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It is said that we see about 59% part of the Moon due to libration. However we must be seeing more than that. My logic is as below. Since the Moon's orbit is inclined to the plane of Sun-Earth by 5 1/2 degree, when Moon is at farthest and lowest point below the plane, we can see beyond the North Pole of Moon from the Earth's North pole and similarly when the Moon is above the Sun-Earth plane we can see much beyond South pole of the Moon from Earth's South Pole. Thus we must be seeing more than 59% due to inclined orbit of Moon.
Piecing Together the Sun & Moon
By: The Editors of Sky & Telescope September 14, 2015 0
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Here’s an easy technique for creating expansive images of the Sun and Moon using modest sensors.
By Tim Jensen in the September 2013 issue of Sky & Telescope
Planetary imagers dream of shooting high-resolution photos rife with small-scale detail. Swirling clouds within Jupiter’s Great Red Spot, or the enigmatic Encke Gap at the edge of Saturn’s ring system, are two trophies we often search for when presented with a high-resolution planetary image. But capturing the same level of detail on full-disk images of the Sun and Moon requires a different approach. By the time you squeeze the entire object down to fit onto the modest detectors in today’s planetary cameras, all that lovely detail is gone. The solution to this problem is to shoot multi-panel mosaics.
The advantage of making high-resolution mosaics is that the tiny details of your narrow field of view will be preserved in a final result. The drawback is that you have to take lots of images or videos and stitch them together to appear as one continuous image. Fortunately, there’s a handy feature in recent versions of Adobe Photoshop CS that can make this stitching almost completely automated.
Shooting large photographs of the Sun and Moon doesn’t require a huge detector in your camera. Author Tim Jensen explains how with a little planning, you can capture and assemble mosaics of the Sun and Moon with small cameras and the Photomerge action in Adobe Photoshop CS. The author assembled the above image from 25 individual tiles recorded with a Canon EOS T2i DSLR and a Celestron C14.
Are you dreaming of getting into astrophotography? Check out our FREE astrophotography ebook, with all the tips and techniques you need to get started.
A Good Plan
Whether you’re shooting the Sun through a 40-mm Personal Solar Telescope or lunar close-ups through a large reflector, plan your approach ahead of time to avoid gaps in your image. Few things are more disappointing than discovering when processing your images hours later that you missed a section of your target! Take the time to roughly calculate how many frames you’ll have to record to completely cover the Sun or Moon with your particular setup. I suggest about a 50% overlap between each of your frames to ensure success. This should give Photoshop plenty of features to match between segments. When including the limb of your subject, position it so that it fills about ¾ of the field of view.
Also consider whether you’ll be shooting with a polar-aligned mount or simply in alt-azimuth mode. Shooting your target with an aligned mount will allow you to shoot your mosaic tiles sequentially in right ascension and declination, ensuring you don’t miss any regions in your final mosaic. This is still possible to do on an alt-azimuth mount, but keep in mind that your subject will appear to rotate as it arcs across the sky during your recordings.
The type of camera you use to shoot your mosaic is inconsequential to your final result, though the best lunar and solar images today are recorded using high-speed video cameras. These videos are then processed using specialized programs that combine the sharpest frames to produce a single image. Recent digital SLR camera models also allow you to record high-definition video that can be processed in the same way.
Once you’ve made your plans and are ready to shoot, choose a well-defined feature to establish focus, such as a distinct lunar crater at one end of the terminator or a dark sunspot. Take your time to sharpen the focus as much as possible. I often sweep through the telescope’s focal point on the video screen a few times before I’m ready to record.
Finally, establish your exposure settings. The solar atmosphere and lunar surface present a wide range of brightness values, so some areas may be unavoidably overexposed, such as solar flares in the chromosphere or bright craters. Choose a region of your subject that is neither extremely bright nor dark as your mid-range value. Don’t change these settings once you begin recording keeping them constant will give each overlapping frame the same brightness and tonality, and you’ll avoid visible seams between each tile.
Once you begin recording your videos, make sure to capture an adequate amount of frames to guarantee you have plenty of sharp ones to stack. This can vary depending on your seeing conditions. I often record 2 to 3,000 frames per video to ensure a sharp result.
When moving from one mosaic section to the next, pick a feature that is about one-third of the way in from the edge you are slewing toward and move it until it’s one-third of the way from the opposite edge.
Calibration Is Key
The biggest key to making an outstanding solar or lunar mosaic is recording a good flat-field calibration frame. Flat-field images record any optical defects in your system, such as dust motes or vignetting in your optical system. This calibration image is then divided into your raw image to cancel out these defects. Most planetary imagers skip this step when shooting close-ups of the planets because their target only covers a portion of the imaging chip, so dust motes or vignetting may be inconsequential to their final result. But when shooting lunar and solar mosaics, these defects need to be corrected to ensure a seamless result.
Left: Among the most important pieces required when stitching together seamless astrophoto mosaics are accurate flat-field calibration frames. This image records any dust donuts or vignetting in your optical system. The result is then mathematically applied to your raw images to correct these errors. Right: The author solved the problem of shooting flats through solar filters by assembling a diffusing screen using a PVC pipe connector and a sheet of white plastic-bag material.
For flats to work properly, you need to shoot them with the exact same camera rotation and focus position as your mosaic tiles, so it’s often easiest to shoot your mosaic tiles first, then record your calibration frames.
Shooting flat-field images for a lunar mosaic is exactly like capturing deep-sky flats. Simply point your scope at an area of the twilight sky that is fairly evenly illuminated and collect some video frames that give a well-lit, but not saturated, field of view. Most advanced video cameras and DSLRs have an option to display a histogram of the image being recorded. Try to expose your flat so the brightest areas peak at roughly 50% of the histogram. Once you’re ready, simply record a video of a few hundred frames that you will then stack into your flat-field image.
Making a flat for solar hydrogen-alpha images is a bit trickier. It’s nearly impossible to find a light source strong enough to shoot a flat through a solar filter. My solution is to use the Sun itself. By placing a diffuser in front of my telescope’s objective, I can blur out details to create good flat-field images. You can use any white material as a diffuser as long as it’s uniform and isn’t completely opaque. A white garbage bag stretched taught over a plastic pipe large enough to fit over your telescope’s objective makes a great diffuser that you can use whenever necessary. To use the diffuser, aim at a bland area of the chromosphere and place the diffuser over the telescope’s objective. Then simply adjust your exposure as described earlier. The additional benefit to using a diffusing cap is that you can switch between shooting flats and lights in seconds.
Putting It All together
Once that you’ve recorded all your videos and calibration frames, the next step is to stack each video to create the mosaic tiles. I prefer to use AviStack 2 (www.avistack.de) to stack my videos, though all planetary-image processing programs have the ability to apply flat-field calibration frames. You may want to refer to your program’s help section to read up on creating flat-field images, but each use a similar process — stack your flat-field video and save the result in the program’s preferred format. Then load the flat-field image into the calibration section of your preferred program. Now simply stack each of your mosaic videos with this flat loaded and it will be applied properly.
When you’ve completed the stacking process, combining the resulting mosaic tiles is extremely easy using the Photomerge function in Photoshop CS3 or higher. Simply open the program and select File / Automate / Photomerge from the pull-down menu. A dialog window opens that first asks you to choose the files or a folder where your mosaic tiles reside. Click the Browse button and navigate to your images. Once you’ve located the mosaic tiles, select them all by clicking the first image at top, hold the shift key, and click the last image on the bottom.
Next, select the “Auto” button in the Layout column. Make sure the Blend Images Together box is checked, hit “OK,” and let Photoshop run its magic. The program will align each image and organize them on a different layer, then create masks to blend them into the final mosaic. This can take several minutes and when it’s done, you’ll have a full mosaic image on the screen. If you had enough overlap between each tile, there should be no gaps visible in the final mosaic.
Assembling your mosaic after stacking and calibrating the individual tiles is easy. Simply open Photoshop’s Photomerge function (File / Automate / Photomerge) and select all your images to combine. All that’s left is to click the “OK” button and wait for the action to complete.
Occasionally, Photomerge does not recognize where a frame should be placed, and leaves it out of the mosaic. If that happens, you can manually insert the frame where it belongs. Open the missing frame, choose Select / All from the pull-down menu, then click your mosaic image and select Edit / Paste. The missing tile will appear in the middle of your mosaic. Select the Move Tool from the tools palette and drag the layer into roughly the proper position. You can then fine-tune the layer’s position by opening the Layers window (Window / Layers) and changing the layer blending mode to Difference. At that point, simply move the layer into its final position with your keyboard’s arrow keys. If the new tile is slightly rotated to the mosaic, you can adjust this by selecting Edit / Transform / Rotate. The layer will appear almost black when aligned. Once you’ve aligned this layer, change the blending mode back to Normal and select Layer / Flatten Image. At this point you can sharpen your result, adjust the color, or do any additional processing you’d usually do to create your high-resolution solar or lunar photos.
Left: If the sharpness varies greatly between tiles or there was inadequate overlap, Photomerge may fail to register pieces of your mosaic. Right: The easiest way to manually register tiles of a mosaic is to paste the missing piece into your image then change the layer blending mode to “Difference.” Simply slide the tile into place using your mouse and keyboard arrow keys. It can be easier to identify where to move your tile if you lower the layer opacity to 50%.
Once you’ve mastered these simple steps, creating large mosaics is a fun way to create full-disk, high-resolution images of the Sun and Moon. Even if you don’t own a large telescope or multi-megapixel camera, you can still produce gorgeous panoramas of the brightest, most detailed objects in our solar system.
When you’re satisfied all your mosaic tiles are properly in position, you can sharpen, colorize, or crop your image just as you would do to any other astrophoto. This 30-frame mosaic of the Sun was captured with the author’s Coronado P.S.T. and a Point Grey Research Flea3 video camera.
Download Your Free Astrophotography Primer Today!
Learn to photograph the solar system and far beyond! If you're itching to get started astrophotography (or know someone who is), you'll want to download our FREE Astrophotography Primer ebook with some essential and easy-to-follow tips!
Tim Jensen is an avid astrophotographer and research project
supervisor for Swinburne Astronomy Online.
Moon During 2019
A mosaic made from 9 individual photos of the Moon captures its phases over one synodic month. For complete details about this image, see Moon Phases Mosaic. The individual images included in this composite can be found in the Moon Phases Gallery. For more composites, see Moon Phases Mosaics. Photo copyright 2012 by Fred Espenak.
We tend to take the Moon for granted but it shares a unique history with Earth. Shortly after its formation 4.5 billion years ago, “proto-Earth” collided with a Mars-sized object called Theia. Much of “proto-Earth” and Theia merged to become our Earth, but the impact also ejected a large amount of material into space. Some of it coalesced to become the Moon (see: Giant Impact Hypothesis).
The Moon’s orbit stabilizes the axial tilt of Earth, preventing it from undergoing chaotic variations that would lead to catastrophic changes in climate. And the daily rise and fall of the Moon-induced tides has left an indelible imprint on Earth. Some scientists even argue whether life on Earth would be possible without the influence of the Moon (see: Without the Moon, Would There Be Life on Earth?).
With this big picture in mind, we gain a new appreciation for the Moon as we watch its phases, cycles, and motions during 2019.
As the Moon orbits Earth, its changing geometry with respect to the Sun produces the Moon’s characteristic phases (New Moon, First Quarter, Full Moon and Last Quarter). One orbit of the Moon relative to the Sun (the synodic month) has a mean duration of 29.5306 days (29 days 12 hours 44 minutes).
The table above lists the date and time of the Moon’s phases throughout 2019. The time of each phase is given in Greenwich Mean Time or GMT (a.k.a. Universal Time or UT). A table of the Moon’s phases covering 100 years on AstroPixels.com can be found at Moon’s Phases – 21st Century (GMT). Similar 100-year tables for other time zones include Eastern Standard Time (EST), Central Standard Time (CST), Mountain Standard Time (MST), and Pacific Standard Time (PST). To convert GMT to other time zones, visit Time Zones.
What surprises many people is that the length of the synodic month (period from New Moon to New Moon) can vary by more than 6 hours from its mean value of 29.5306 days (29 days 12 hours 44 minutes). The table below gives the date of New Moon, the length of the synodic month, and the difference from the synodic month’s mean value for every synodic month in 2019. For instance, the eighth synodic month of 2019 (beginning Aug 01) is 5 hours 19 minutes shorter than the mean while the first synodic month (beginning Jan 06) is 6 hours 51 minutes longer than the mean.
What causes these variations? The explanation involves the Moon’s elliptical orbit and its orientation with respect to the Sun during any given month. If New Moon occurs when the Moon is nearest to Earth (perigee), then the synodic month is shorter than normal. On the other hand, if New Moon occurs when the Moon is farthest from Earth (apogee), then the synodic month is longer than normal. Furthermore, the orientation of the Moon’s ellipse-shaped orbit slowly rotates in space with a period of about 18 years. A more detailed discussion on this topic can be found at Moon’s Orbit and the Synodic Month (EclipseWise.com). You can also find the duration of every synodic month this century at Length of the Synodic Month: 2001 to 2100 (AstroPixels.com).
The time it takes for the Moon to orbit once with respect to its perigee is known as the anomalistic month. Its average length is 27.55455 days (27 days 13 hours 19 minutes), which is nearly 2 days less than the synodic month. The actual length can vary by several days due to the gravitational effects of the Sun on the Moon’s elliptical orbit. The table below gives the date and time of every perigee and apogee of the Moon during 2019. The Moon’s distance (in kilometers) is also given. The ‘m’ or ‘M’ appearing next to a date indicates the minimum or maximum distance, respectively, for the year. A table listing details of every perigee and apogee this century can be found at Perigee and Apogee: 2001 to 2100 (AstroPixels.com)
Because the Moon orbits Earth in about 29.5 days with respect to the Sun, its daily motion against the background stars and constellations is quite rapid, averaging 12.2° per day. A table giving the Moon’s daily celestial coordinates throughout the year can be found at Moon Ephemeris for 2019 (AstroPixels.com). This table lists many other details about the Moon including its daily distance, apparent size, libration, phase age (days since New Moon) and the phase illumination fraction.
A Perigean Full Moon (Full Moon near Perigee or closest point to Earth) took place on Dec. 13, 2016. The media loves to call this a “Super Moon” but I prefer to call it the less sensational “Perigean Full Moon” or “Full Moon near perigee”. Whatever you call it, it’s a chance to take a moment and marvel at our beautiful natural satellite. The photo below was taken from my driveway in Portal, AZ as the Moon rose above the Peloncillo Mountains of New Mexico. I was hoping for a completely clear sky but the clouds actually added an appealing element to the scene. Copyright 2016 by Fred Espenak.
When a Full Moon occurs within 90% of the Moon’s closest approach to Earth in a given orbit, it is called a Perigean Full Moon or more commonly a Super Moon. The Full Moon then appears especially big and bright because it subtends its largest apparent diameter as seen from Earth. The table below lists the Perigean Full Moons (Super Moons) occurring in 2019.
The Relative Distance listed in the Super Moon table expresses the Moon’s distance as a fraction between apogee (0.0) and perigee (1.0). For more information on Super Moons and a complete list of them for this century, see Full Moon at Perigee (Super Moon): 2001 to 2100 (AstroPixels.com).
Besides its obvious phases, the Moon also undergoes some additional extremes in its orbit including: Perigee and Apogee, Ascending/Descending Nodes, and Lunar Standstills. Each of these AstroPixels links covers lunar phenomena for the entire 21st Century.
As the Moon orbits Earth, its changing geometry with respect to the Sun produces the characteristic phases. This composite image is a mosaic made from 25 individual photos of the Moon and illustrates its phases over one synodic month. For complete details about this image, see Moon Phases Mosaic. The individual images included in this composite can be found in the Moon Phases Gallery. For more composites, see Moon Phases Mosaics. Photo copyright 2012 by Fred Espenak.
One of the first projects I tackled upon completing Bifrost Observatory in 2010 was to photograph the Moon’s phases every day for a complete month. Of course, the weather doesn’t always cooperate (even from sunny Arizona) so it actually took several months to complete the project. You can see the results at the Moon Phases Gallery. Clicking on any of the thumbnail pictures will give you an enlarged image with complete technical details. You can also visit Moon Phases Mosaics to see composites showing the Moon’s phases over a complete synodic month.
The NASA/Goddard Scientific Visualization Studio has used image data from the Lunar Reconnaissance Orbiter (LRO) mission to create clever animations of the Moon’s ever changing phases and librations in 2019. The example below illustrates the Moon’s phase and libration at hourly intervals throughout 2019, as viewed from the northern hemisphere. Each frame represents one hour.
And not to be accused of northern hemisphere chauvinism, here is a version as seen from the southern hemisphere.
Besides presenting the Moon’s phase and apparent size, these videos show the Moon’s orbital position, sub-Earth and sub-solar points, distance from the Earth at true scale, and labels of craters near the terminator. As the Moon orbits Earth, it appears to wobble and tip on its axis. This motion is called libration and it allows us to see about 59% of the Moon’s surface (see Libration (EarthSky)). The major cause of libration is due to our changing line of sight because of the Moon’s elliptical orbit.
Ernie Wright of the NASA Scientific Visualization Studio has also used LRO data to create a web tool called Dial-A-Moon. Enter the month, day and hour and Dial-A-Moon will generate a visualization of the Moon showing the correct phase and libration for that instant during 2019 (see Moon Phase and Libration, 2019).
Finally, what discussion of the Moon would be complete without mentioning eclipses in 2019? There are two eclipses of the Moon. The first is a total eclipse on January 21, which is visible from North and Soth America as well as Western Europe. The second lunar eclipse is partial on July 16 and is visible from the Eastern Hemisphere.
There are also three solar eclipses in 2019. The first is a partial eclipse on January 06, visble from Siberia and Alaska. The next is a total eclipse on July 02. The Total phase of the eclipse is visible from the South Pacific, Chile, and Argentina. The last eclipse is an annular eclipse on December 26 and visible prom parts of the Eastern Hemisphere.
For more details on all these events, see Eclipses During 2019 (EclipseWise.com).
For those who are new to Moon watching, many are surprised that the entire Moon can often be seen during the crescent phase. The pale glow illuminating the unlit part of a crescent Moon is light reflected from Earth and it’s called earthshine. The time-lapse movie above captures earthshine during moonset back one evening in May 2015. Read more about earthshine in this Earth&Sky article.
Watching the Moon’s phases wax and wane as well as the occasional lunar eclipse can best be enjoyed with the naked eye and binoculars. And you don’t even need a dark sky since the Moon is easily visible from the heart of brightly lit cities.
The Moon phases and lunar phenomena discussed here were all generated with computer programs I’ve written (THINK Pascal and FORTRAN 90 running on a Macintosh G4 and MacBook Pro) using Astronomical Algorithms (Jean Meeus).
Eclipse Day Checklist
- Basic Checklist
- Equipment Checklist for Viewing and/or Photographing Eclipse
- Binoculars and/or small telescope
- Solar filters for binoculars and/or telescope
- Camera equipment and tripod
- Video camera and tripod
- Audio recorder for your comments and impressions or to capture reactions of people or wildlife near you
- Audio recorder with prerecorded messages timed to cue you about what to see next*
- Extra batteries for all of the above
- Pencil and paper to record impressions or to sketch (also to take down the names and addresses of fellow observers)
A composite image of the total solar eclipse of 2006 March 29 was shot in Jalu, Libya. It was produced from 26 individual exposures obtained with two separate telescopes and combined with computer software to reveal subtle details in the corona. Copyright 2006 by Fred Espenak.
10 interesting facts about Earth you should know
Before telling some interesting facts about Earth, let me narrate – We live on planet Earth. It is our homeland which feeds us, provides us all sorts of amenities, and makes us live joyfully. As much as we know, it is the only planet which supports all circumstances of creation of life. Earth provides us many invaluable things to sustain life such as oxygen, water and other life carrying factors. It will not be exaggeration to say that Earth is like our mother which nurtures us in its best possible way.
In some ancient mythologies such as in ancient India, Earth is regarded as a goddess. Even today many people worship Earth and feel obliged for what Earth has provided them. In spite of this, many people don’t know much about it. Here, I am going to present some interesting facts about the Earth which you will like. Just go through the page.
1. The enormous size of Earth but not too enormous before Sun or Universe:
The size of our home planet is very huge. It has a radius of 6371 Km. If we compare the size of the earth with our’s, it is very big. But in this universe, its size is not more than a billionth fraction of a sand particle or probably even smaller than that. The Sun, which is the largest celestial body in our solar system, has the radius 109 times larger than our Earth. Weight of Sun is also 333000 times as much as Earth. It is estimated that 1300000 piles of the earth are equivalent to a single Sun.
2. We are in the third place from the Sun:
Our home planet, Earth is in the third position from the Sun. This distance is so optimized naturally that it is just sufficient to support life. Any variation in this distance will make Earth too hot or too cold to allow life to propagate. At this location, every factor necessary to the survival of organisms exists abundantly. Unlimited oxygen, unlimited water, and many other natural gifts are bestowed to us only due to the perfect distance of Earth from the Sun.
3. Earth is not a young guy, it’s too old:
Do you think that you are older enough to be called grandpa by children? Think about the age of Earth. Using modern technologies, scientists have calculated it and announced that it is approximately 4.54 billion years. Isn’t it mind-blowing? Our life span is quite negligible before that. We are like “nothing”. Isn’t it quite surprising that we plan more and more for our negligible life span? Even with respect to size, we are “nothing”, but thanks to our ego, we think that we are the center of the universe!!
4. Earth had two moons that merged to form a single moon:
Can you imagine, once upon a time, Earth was the owner of two moons. According to some researchers, these two moons of Earth slammed into each other and formed a single moon. This single moon is what we see today as a lunar satellite of Earth. This theory of two moons justifies the cause why two sides of the moon have different interfaces.
5. Earth’s rotation is gradually slowing:
When I say Earth rotates about its own axis, what is new in it? All of us know that. But what makes you puzzled is that Earth’s rotation is slowing down by few milliseconds per day. This has a direct consequence on the lengthening of the day. It is estimated that after 140 million years later, the duration of the day will increase by 25 hours. Some scientists have associated recent earthquakes with that change in rotation of Earth.
6. We are living on the densest planet of the solar system:
Yes, you heard it correctly. You are living on the densest planet of the solar system. Don’t believe it yet? Just consult the data as taken from NASA as given below. This information is something that also made my jaw dropped. Can you tell me why the density of Earth is more than any other mate planets? Pen down in comment section if you know..
7. Is another Sun hidden in the core of Earth:
All of us know very well that the Sun is hot but you might be unaware of the fact that the core of the Earth has very high temperature and it is equivalent to the temperature of the Sun. The temperature is approximately 6000 degrees Celsius. Do you know that the magnetic property of the Earth is due to its core? May God not do that but if somehow, the core becomes cool, the magnetism of the Earth will get terminated and the whole system of circumstances responsible for life will get distorted. It will not take much time to end life on Earth.
8. The surface of the Earth is in a continuous process of transformation:
The surface of the Earth is recycled again and again. Every moment, it is in the continuous process of transformation. The rocks on the earth transform itself from one type to another type of rock due to internal and external factors. Igneous rocks transform into sedimentary rocks which further transform into metamorphic rocks and this process continues into cyclic order. So, as our body transforms itself into new cells, in the same manner, Earth transforms itself into new rocks.
9. First photo of Earth from space?
The image shown above is the first photo of Earth taken from space. On October 24, 1946, a German rocket launched from White Sands Missile Range carrying a 35 mm motion picture camera. After reaching an altitude of 65 miles, the camera fell back to Earth and destroyed, however, the film survived.
10. Epic picture of Moon crossing Earth:
This amazing picture was taken by NASA’s Earth Polychromatic Imaging Camera(EPIC) installed on Deep Space Climate Observatory (DSCOVR) satellite. What is special in this image? In this image, the “dark side” of the moon is visible which can never be seen from Earth. The dark side of the moon is also called the “far side of the Moon”.We are able to see only 59% of Moon. The remaining portion can’t be seen from the Earth.
Observing conditions: definitions
The following definitions of the observing conditions are common between Phase 1 preparation and Phase 2 preparation, as well as between Service Mode and Visitor Mode observations. These basic definitions are listed below. Please use the instrument selector on the right to see instrument-specific information at the bottom of the page. There are additional Service Mode Policies and Service Mode Guidelines regarding the observing conditions.
Observing conditions (Sky Transparency, Moon, PWV, as well as Turbulence Category, and Image Quality) are defined as follows:
- Sky Transparency
- Photometric: No visible clouds, transparency variations under 2%, only assessable by the analysis of photometric standard stars.
- Clear: Less than 10% of the sky (above 30 degrees elevation) covered in clouds, transparency variations under 10%.
- Thin cirrus: transparency variations above 10%.
Important note on the moon distance constraint for optical wavelengths:
At the dry, low water vapour site of Paranal during clear or photometric nights we expect that the night sky brightness does not show a strong dependence of the lunar distance (Rayleigh scattering I
Measurements performed on Paranal in I-band during bright time have shown that the sky brightness is approximately constant for moon distances >
50deg. Hence, defining a moon distance constraint larger than 50 deg for I-band observations are unnecessarily limiting the time available for the execution. Observations at shorter wavelengths (B- to R-band) in grey and dark time are also not affected very much by the presence of the moon if the distance is >
50-60 deg, and often the sky is darker at 60-70 deg away from the moon than at 120 deg away, when the moon is low above the horizon (see Fig 5 of Patat 2004, Messenger Issue 118)
For observations in optical wavelengths it is advised to select moon distance up to 60-70 degrees. Selecting larger lunar distances may drastically reduce the gray/dark time periods in which the observations can be carried out.
- Acceptable upper limits for the PWV must be specified for all instruments in the new p1 proposal submission system, when defining the corresponding observing run. The default values are 10mm for VISIR, 20mm for KMOS, and 30mm for all other Paranal instruments. These defaults should be fine for all non-IR instruments and in any event can be lowered if required for the science. The impact of the PWV can be evaluated with Exposure Time Calculators (ETCs).
- Turbulence Category, Image Quality, and their usage at Phase 1 and Phase 2 are defined as follows:
- As a preface, seeing is an inherent property of the atmospheric turbulence, which is independent of the telescope that is observing through the atmosphere outside the dome. The seeing values in the table and figure below are measured in the V band at zenith.
- Image Quality (IQ),defined as the full width at half maximum (FWHM) of long-exposure stellar images, is a property of the images obtained in the focal plane of an instrument mounted on a telescope observing through the atmosphere. It is therefore a quantity measured at the (requested) airmass and wavelength of observation.
- Turbulence Category
- Starting with Phase 1 of ESO Period 105 (Sept 2019), we introduce a new constraint, the atmospheric turbulence constraint. This constraint generalizes the classical seeing constraint used so far, and takes into account the coherence time and the fraction of turbulence in the ground layer, for instruments that need it, in addition to the classical seeing. These additions are important constraints for instruments using adaptive optics (AO) and need to be taken into account when scheduling observations to ensure that the science goals can be achieved. In order to harmonize this new scheme between all non-AO and AO instruments, a single Turbulence Category is introduced at Phase 1 for all instruments.
- Turbulence Category at Phase 1 for any instrument: At Phase 1, the classical seeing constraint is replaced by the choice of the Turbulence Category for all instruments. The Turbulence Category is defined by its probability of occurrence, from 10%, meaning the top 10% of the best conditions in La Silla or Paranal (the most demanding category), to 100% meaning any conditions. The following 7 Turbulence Categories have been defined allowing one to select from a range of good turbulence conditions as appropriate and encouraging requests for demanding science cases:
(name and probability)
10% 20% 30% 50% 70% 85% 100%
- Turbulence Category at Phase 1 for instruments without AO system: For instruments without AO systems, for which the only relevant turbulence parameter is the classical seeing (i.e. for Paranal: UVES, FLAMES, XSHOOTER, FORS2, KMOS, MUSE WFM without AO, HAWKI without AO, CRIRES without AO VISIR, ESPRESSO, VIRCAM, and VISTA), each Turbulence category can therefore be associated to a unique seeing upper threshold. These thresholds have been computed using the cumulative distribution of the seeing assuming on average 1h long observations:
Turbulence Category 10% 20% 30% 50% 70% 85% 100% Seeing threshold 0.5" 0.6" 0.7" 0.8" 1.0" 1.3" all
These 7 Turbulence Categories are shown graphically in the Figure below along with the cumulative distribution of the seeing computed after applying a rolling 90-th percentile over 1h:
- Instruments without AO systems or with ground layer AO systems (MUSE WFM-AO and HAWKI+GRAAL): the image quality (IQ) remains the constraint for Service Mode Phase 2 Observation Blocks (OBs) and there is no change with respect to past observing periods. Quality control grade A is assigned to executed OBs if constraints are fully met, and they are graded B if the measured IQ is violated up to 10%. If constraints are violated by more than 10% within the 1h of the start of observation, the quality grade will be C and the observation will be repeated.
With the help of the Exposure Time Calculators (ETCs) the requested Phase 1 V-band seeing at zenith can be transformed into the desired IQ at the observed wavelength and airmass for each instrument.
- Instruments with AO systems (SPHERE, MUSE NFM, CRIRES, VLTI instruments): the same Turbulence Categories as defined at Phase 1 are used at Phase 2. An observation will be considered successfully executed if the turbulence conditions associated to this Turbulence Category are met during the observation. More precisely, if the constraints are met during 90% of the time, the quality grade of the observation will be A. If the constraints are met during 50% of the time, the quality grade will be B. In other cases, the quality grade will be C and the observation will be repeated.
Please note that while for each instrument/mode the constraint specification at Phase 1 is the Turbulence Category, at Phase 2 the corresponding constraint is (instead) as specified in the table below (Turbulence Category or Image Quality), depending on instrument and AO mode. In any event, the specification at Phase 2 should be no tighter than the Phase 1 specification (see Service Mode Policies).
The correspondence between Phase 1 and Phase 2 characterisations of the Turbulence Category and Image Quality follows this table, where the definitions of Turbulence Category and Image Quality are as described above
HAWK-I MUSE SPHERE CRIRES VLTI Other Phase 1 Turbulence Category Turbulence Category Turbulence Category Turbulence Category Turbulence Category Turbulence Category Phase 2 No-AO Image Quality Image Quality N/A Image Quality N/A Image Quality GLAO Image Quality Image Quality N/A N/A N/A N/A Full-AO N/A Turbulence Category Turbulence Category Turbulence Category Turbulence Category N/A
The two figures below show the percent chance of realisation of combined sky transparency (clear sky or better left thin clouds or better on the right) conditions and instantaneous measurement of different seeing values, across the year at Paranal. The black line through the middle represents the 50% chance of realisation. See also the Messenger article "Fifteen Years of Service Mode Operations: Closing the Loop with the Community" by F. Primas et al. (2015).
10 reasons we should be exploring space
Space exploration involves great economic investment, massive risks and seemingly impossible objectives. So why should we commit ourselves to it? Because it can benefit us, as individuals and as a species, in unexpected ways.
1) It protects us from asteroids
The asteroid threat may be manna from heaven for the catastrophists, but it has to be taken into consideration: a serious and well-funded space programme must have the capacity to monitor large asteroids that could potentially destroy our planet. Small asteroids break up in the atmosphere at the rate of one every fortnight, but there are some that are over 100 metres in diameter that we should keep an eye on. Fortunately, we already have instruments that allow us (in most cases) to predict and study asteroids’ transit.
2) It safeguards our health
From a robotic arm that can work directly using functional magnetic resonance imaging (FMRI) to methods of administering anti-cancer drugs aimed directly at diseased cells, research in microgravity has brought about important innovations in the field of medicine. Today, one of the most promising sectors is research into osteoporosis – a condition that causes a loss of bone mass, which means that bones become weak and more likely to break. Not only does this afflict the elderly (particularly women) – it also affects astronauts on the International Space Station (ISS). After one month’s exposure to microgravity, an astronaut loses about 1.5 per cent of his bone mass, the same percentage as that lost by an elderly person over the course of a year. Not only is there, therefore, plenty of opportunity to trial new anti-osteoporosis drugs and treatments in space, it’s also a lot easier to do so than it is on Earth.
Why Does the Moon Have Phases?
For millennia, humans have kept track of time by observing the changing face of the moon. In fact, you may have noticed that the word "moon" shares its first few letters with the word "month" — and that's no coincidence.
The phases of the moon — new moon, first quarter, full moon and last quarter — repeat themselves about once every month. But why does the moon have phases at all? To answer this question, it's necessary to understand two important facts. First of all, the moon revolves around the Earth once every 29.5 days. And secondly, as the moon carries out its voyage around the planet, it's lit from varying angles by the sun.
One half of the moon is always illuminated by the sun. But here on Earth, we can't always see the half of the moon that's lit up. What we call the phases of the moon represent the different fractions of the moon's lighted half that we can see as the moon circles the Earth. [See this infographic on Moon Phases]
When the moon and the sun are on opposite sides of the Earth, we perceive the moon as full. However, when the sun and the moon are on the same side of the Earth, we say the moon is "new." During a new moon, the side of the moon that we can see from Earth is not illuminated by direct sunlight at all.
Between the new moon and the full moon, the moon is a crescent (less than half illuminated). It then waxes — grows bigger — into a half-moon (half-illuminated). The first half moon after the new moon is called the first quarter because at that point, the moon is one-quarter of the way through its monthly cycle of phases. After the first quarter comes the gibbous moon (more than half illuminated) and finally a full moon.
This cycle of phases then repeats itself in reverse. After a full moon, the moon wanes — becomes smaller — into a gibbous moon, a half-moon (also called last quarter), a crescent and finally a new moon.
Just before and just after the new moon, when a slim crescent of the moon is lit, you can also see the rest of the moon lit dimly. This owes to sunlight that bounces off the Earth and illuminates the otherwise dark portion of the moon that&rsquos facing us, an effect known as "earthshine."
The major phases of the moon — new moon, first quarter, full moon, last quarter and next new moon — occur, on average, about 7.4 days apart. If you need some help tracking these phases yourself (or if you want to see where the moon was on an important day in history), NASA provides an online calendar of the dates and times of all phases of the moon for the six thousand year period between 2000 BCE to 4000 CE.
Early years Edit
Clarke was born in Minehead, Somerset, England,  and grew up in nearby Bishops Lydeard. As a boy, he lived on a farm, where he enjoyed stargazing, fossil collecting, and reading American science-fiction pulp magazines. He received his secondary education at Huish school in Taunton. Some of his early influences included dinosaur cigarette cards, which led to an enthusiasm for fossils starting about 1925. Clarke attributed his interest in science fiction to reading three items: the November 1928 issue of Amazing Stories in 1929 Last and First Men by Olaf Stapledon in 1930 and The Conquest of Space by David Lasser in 1931. 
In his teens, he joined the Junior Astronomical Association and contributed to Urania, the society's journal, which was edited in Glasgow by Marion Eadie. At Clarke's request, she added an Astronautics Section, which featured a series of articles written by him on spacecraft and space travel. Clarke also contributed pieces to the Debates and Discussions Corner, a counterblast to an Urania article offering the case against space travel, and also his recollections of the Walt Disney film Fantasia. He moved to London in 1936 and joined the Board of Education as a pensions auditor.  Some fellow science-fiction writers and he shared a flat in Gray's Inn Road, where he got the nickname "Ego" because of his absorption in subjects that interested him,  and later named his office filled with memorabilia as his "ego chamber". 
World War II Edit
During the Second World War from 1941 to 1946, he served in the Royal Air Force as a radar specialist and was involved in the early-warning radar defence system, which contributed to the RAF's success during the Battle of Britain. Clarke spent most of his wartime service working on ground-controlled approach (GCA) radar, as documented in the semiautobiographical Glide Path, his only non-science-fiction novel. Although GCA did not see much practical use during the war, it proved vital to the Berlin Airlift of 1948–1949 after several years of development. Clarke initially served in the ranks, and was a corporal instructor on radar at No. 2 Radio School, RAF Yatesbury in Wiltshire. He was commissioned as a pilot officer (technical branch) on 27 May 1943.  He was promoted flying officer on 27 November 1943.  He was appointed chief training instructor at RAF Honiley in Warwickshire and was demobilised with the rank of flight lieutenant.
After the war, he attained a first-class degree in mathematics and physics from King's College London.    After this, he worked as assistant editor at Physics Abstracts.  Clarke then served as president of the British Interplanetary Society from 1946 to 1947 and again from 1951 to 1953. 
Although he was not the originator of the concept of geostationary satellites, one of his most important contributions in this field may be his idea that they would be ideal telecommunications relays. He advanced this idea in a paper privately circulated among the core technical members of the British Interplanetary Society in 1945. The concept was published in Wireless World in October of that year.  Clarke also wrote a number of nonfiction books describing the technical details and societal implications of rocketry and space flight. The most notable of these may be Interplanetary Flight: An Introduction to Astronautics (1950), The Exploration of Space (1951), and The Promise of Space (1968). In recognition of these contributions, the geostationary orbit 36,000 kilometres (22,000 mi) above the equator is officially recognised by the International Astronomical Union as the Clarke Orbit. 
His 1951 book, The Exploration of Space, was used by the rocket pioneer Wernher von Braun to convince President John F. Kennedy that it was possible to go to the Moon. 
Following the 1968 release of 2001, Clarke became much in demand as a commentator on science and technology, especially at the time of the Apollo space program. On 20 July 1969, Clarke appeared as a commentator for the CBS News broadcast of the Apollo 11 moon landing.  
Sri Lanka and diving Edit
Clarke lived in Sri Lanka from 1956 until his death in 2008, first in Unawatuna on the south coast, and then in Colombo.  Initially, his friend Mike Wilson and he travelled around Sri Lanka, diving in the coral waters around the coast with the Beachcombers Club. In 1957, during a dive trip off Trincomalee, Clarke discovered the underwater ruins of a temple, which subsequently made the region popular with divers.  He subsequently described it in his 1957 book The Reefs of Taprobane. This was his second diving book after the 1956 The Coast of Coral.  Though Clarke lived mostly in Colombo, he set up a small diving school and a simple dive shop near Trincomalee. He dived often at Hikkaduwa, Trincomalee, and Nilaveli. 
The Sri Lankan government offered Clarke resident guest status in 1975.  He was held in such high esteem that when fellow science-fiction writer Robert A. Heinlein came to visit, the Sri Lanka Air Force provided a helicopter to take them around the country.  In the early 1970s, Clarke signed a three-book publishing deal, a record for a science-fiction writer at the time. The first of the three was Rendezvous with Rama in 1973, which won all the main genre awards  and spawned sequels that along with the 2001 series formed the backbone of his later career.
In 1988, he was diagnosed with post-polio syndrome, having originally contracted polio in 1962, and needed to use a wheelchair most of the time thereafter.  Clarke was for many years a vice-patron of the British Polio Fellowship. 
In the 1989 Queen's Birthday Honours, Clarke was appointed Commander of the Order of the British Empire (CBE) "for services to British cultural interests in Sri Lanka".  The same year, he became the first chancellor of the International Space University, serving from 1989 to 2004. He also served as chancellor of Moratuwa University in Sri Lanka from 1979 to 2002.
In 1994, Clarke appeared in a science-fiction film he portrayed himself in the telefilm Without Warning, an American production about an apocalyptic alien first-contact scenario presented in the form of a faux newscast.
Clarke also became active in promoting the protection of gorillas and became a patron of the Gorilla Organization, which fights for the preservation of gorillas.  When tantalum mining for mobile phone manufacture threatened the gorillas in 2001, he lent his voice to their cause.  The dive shop that he set up continues to operate from Trincomalee through the Arthur C Clarke Foundation. 
Television series host Edit
Personal life Edit
On a trip to Florida in 1953,  Clarke met and quickly married Marilyn Mayfield, a 22-year-old American divorcee with a young son. They separated permanently after six months, although the divorce was not finalised until 1964.  "The marriage was incompatible from the beginning," said Clarke.  Clarke never remarried, but was close to a Sri Lankan man, Leslie Ekanayake (13 July 1947 – 4 July 1977), whom Clarke called his "only perfect friend of a lifetime" in the dedication to his novel The Fountains of Paradise. [a] Clarke is buried with Ekanayake, who predeceased him by three decades, in Colombo's central cemetery.  In his biography of Stanley Kubrick, John Baxter cites Clarke's homosexuality as a reason why he relocated, due to more tolerant laws with regard to homosexuality in Sri Lanka.  In 1998, the Sunday Mirror reported that he paid Sri Lankan boys for sex, leading to the cancellation of plans for Prince Charles to knight him on a visit to the country.   The accusation was subsequently found to be baseless by the Sri Lankan police.   Journalists who enquired of Clarke whether he was gay were told, "No, merely mildly cheerful."  However, Michael Moorcock wrote:
Everyone knew he was gay. In the 1950s, I'd go out drinking with his boyfriend. We met his protégés, western and eastern, and their families, people who had only the most generous praise for his kindness. Self-absorbed he might be and a teetotaller, but an impeccable gent through and through. 
In an interview in the July 1986 issue of Playboy magazine, when asked if he had had a bisexual experience, Clarke stated, "Of course. Who hasn't?"  In his obituary, Clarke's friend Kerry O'Quinn wrote: "Yes, Arthur was gay . As Isaac Asimov once told me, 'I think he simply found he preferred men.' Arthur didn't publicise his sexuality – that wasn't the focus of his life – but if asked, he was open and honest." 
Clarke accumulated a vast collection of manuscripts and personal memoirs, maintained by his brother Fred Clarke in Taunton, Somerset, England, and referred to as the "Clarkives". Clarke said some of his private diaries will not be published until 30 years after his death. When asked why they were sealed, he answered, "Well, there might be all sorts of embarrassing things in them." 
On 26 May 2000, he was made a Knight Bachelor "for services to literature" at a ceremony in Colombo.  [b]  The award of a knighthood had been announced in the 1998 New Year Honours list,   but investiture with the award had been delayed, at Clarke's request, because of an accusation by the British tabloid the Sunday Mirror of paying boys for sex.   The charge was subsequently found to be baseless by the Sri Lankan police.   According to The Daily Telegraph, the Mirror subsequently published an apology, and Clarke chose not to sue for defamation.  The Independent reported that a similar story was not published, allegedly because Clarke was a friend of newspaper tycoon Rupert Murdoch.  Clarke himself said, "I take an extremely dim view of people mucking about with boys", and Rupert Murdoch promised him the reporters responsible would never work in Fleet Street again.  Clarke was then duly knighted.
Later years Edit
Although he and his home were unharmed by the 2004 Indian Ocean earthquake tsunami, his "Arthur C. Clarke Diving School" (now called "Underwater Safaris")  at Hikkaduwa near Galle was destroyed.  He made humanitarian appeals, and the Arthur C. Clarke Foundation worked towards better disaster notification systems. 
Because of his post-polio deficits, which limited his ability to travel and gave him halting speech, most of Clarke's communications in his last years were in the form of recorded addresses. In July 2007, he provided a video address for the Robert A. Heinlein Centennial in which he closed his comments with a goodbye to his fans. In September 2007, he provided a video greeting for NASA's Cassini probe's flyby of Iapetus (which plays an important role in the book of 2001: A Space Odyssey).  In December 2007 on his 90th birthday, Clarke recorded a video message to his friends and fans bidding them good-bye. 
Clarke died in Sri Lanka on 19 March 2008 after suffering from respiratory failure, according to Rohan de Silva, one of his aides.     His aide described the cause as respiratory complications and heart failure stemming from post-polio syndrome. 
Just hours before Clarke's death, a major gamma-ray burst (GRB) reached Earth. Known as GRB 080319B, the burst set a new record as the farthest object that can be seen from Earth with the naked eye.  It occurred about 7.5 billion years ago, the light taking that long to reach Earth.  Larry Sessions, a science writer for Sky and Telescope magazine blogging on earthsky.org, suggested that the burst be named the "Clarke Event".   American Atheist Magazine wrote of the idea: "It would be a fitting tribute to a man who contributed so much, and helped lift our eyes and our minds to a cosmos once thought to be province only of gods." 
A few days before he died, he had reviewed the manuscript of his final work, The Last Theorem, on which he had collaborated by e-mail with contemporary Frederik Pohl.  The book was published after Clarke's death.  Clarke was buried alongside Leslie Ekanayake in Colombo in traditional Sri Lankan fashion on 22 March. His younger brother, Fred Clarke, and his Sri Lankan adoptive family were among the thousands in attendance. 
While Clarke had a few stories published in fanzines, between 1937 and 1945, his first professional sale appeared in Astounding Science Fiction in 1946: "Loophole" was published in April, while "Rescue Party", his first sale, was published in May. [c] Along with his writing, Clarke briefly worked as assistant editor of Science Abstracts (1949) before devoting himself in 1951 to full-time writing.
Clarke began carving out his reputation as a "scientific" science-fiction writer with his first science-fiction novel, Against the Fall of Night, published as a novella in 1948. It was very popular and considered ground-breaking work for some of the concepts it contained. Clarke revised and expanded the novella into a full novel, which was published in 1953. Clarke later rewrote and expanded this work a third time to become The City and the Stars in 1956, which rapidly became a definitive must-read in the field. His third science-fiction novel, Childhood's End, was also published in 1953, cementing his popularity. Clarke capped the first phase of his writing career with his sixth novel, A Fall of Moondust, in 1961, which is also an acknowledged classic of the period.
During this time, Clarke corresponded with C. S. Lewis in the 1940s and 1950s and they once met in an Oxford pub, the Eastgate, to discuss science fiction and space travel. Clarke voiced great praise for Lewis upon his death, saying the Ransom trilogy was one of the few works of science fiction that should be considered literature. 
"The Sentinel" Edit
In 1948, he wrote "The Sentinel" for a BBC competition. Though the story was rejected, it changed the course of Clarke's career. Not only was it the basis for 2001: A Space Odyssey, but "The Sentinel" also introduced a more cosmic element to Clarke's work. Many of Clarke's later works feature a technologically advanced but still-prejudiced mankind being confronted by a superior alien intelligence. In the cases of Childhood's End, and the 2001 series, this encounter produces a conceptual breakthrough that accelerates humanity into the next stage of its evolution. This also applies in the far-distant past (but our future) in The City and the Stars (and its original version, Against the Fall of Night).
In Clarke's authorised biography, Neil McAleer writes: "many readers and critics still consider Childhood's End Arthur C. Clarke's best novel."  But Clarke did not use ESP in any of his later stories, saying, "I've always been interested in ESP, and of course, Childhood's End was about that. But I've grown disillusioned, partly because after all this time, they're still arguing about whether these things happen. I suspect that telepathy does happen." 
A collection of early essays was published in The View from Serendip (1977), which also included one short piece of fiction, "When the Twerms Came". Clarke also wrote short stories under the pseudonyms of E. G. O'Brien and Charles Willis.  Almost all of his short stories can be found in the book The Collected Stories of Arthur C. Clarke (2001).
"Big Three" Edit
For much of the later 20th century, Clarke, Asimov, and Heinlein were informally known as the "Big Three" of science-fiction writers.  Clarke and Heinlein began writing to each other after The Exploration of Space was published in 1951, and first met in person the following year. They remained on cordial terms for many years, including visits in the United States and Sri Lanka.
Clarke and Asimov first met in New York City in 1953, and they traded friendly insults and gibes for decades. They established an oral agreement, the "Clarke–Asimov Treaty", that when asked who was better, the two would say Clarke was the better science-fiction writer and Asimov was the better science writer. In 1972, Clarke put the "treaty" on paper in his dedication to Report on Planet Three and Other Speculations.  
In 1984, Clarke testified before Congress against the Strategic Defense Initiative (SDI).  Later, at the home of Larry Niven in California, a concerned Heinlein attacked Clarke's views on United States foreign and space policy (especially the SDI), vigorously advocating a strong defence posture. Although the two later reconciled formally, they remained distant until Heinlein's death in 1988. 
2001 series of novels Edit
2001: A Space Odyssey, Clarke's most famous work, was extended well beyond the 1968 movie as the Space Odyssey series. In 1982, Clarke wrote a sequel to 2001 titled 2010: Odyssey Two, which was made into a film in 1984. Clarke wrote two further sequels which have not been adapted into motion pictures: 2061: Odyssey Three (published in 1987) and 3001: The Final Odyssey (published in 1997).
2061: Odyssey Three involves a visit to Halley's Comet on its next plunge through the Inner Solar System and a spaceship crash on the Jovian moon Europa. The whereabouts of astronaut Dave Bowman (the "Star Child"), the artificial intelligence HAL 9000, and the development of native life on Europa, protected by the alien Monolith, are revealed.
Finally, in 3001: The Final Odyssey, astronaut Frank Poole's freeze-dried body, found by a spaceship beyond the orbit of Neptune, is revived by advanced medical science. The novel details the threat posed to humanity by the alien monoliths, whose actions are not always as their builders had intended.
2001: A Space Odyssey Edit
Clarke's first venture into film was 2001: A Space Odyssey, directed by Stanley Kubrick. Kubrick and Clarke had met in New York City in 1964 to discuss the possibility of a collaborative film project. As the idea developed, they decided to loosely base the story on Clarke's short story, "The Sentinel", written in 1948 as an entry in a BBC short-story competition. Originally, Clarke was going to write the screenplay for the film, but Kubrick suggested during one of their brainstorming meetings that before beginning on the actual script, they should let their imaginations soar free by writing a novel first, on which they would base the film. "This is more or less the way it worked out, though toward the end, novel and screenplay were being written simultaneously, with feedback in both directions. Thus, I rewrote some sections after seeing the movie rushes – a rather expensive method of literary creation, which few other authors can have enjoyed."  The novel ended up being published a few months after the release of the movie.
Due to the hectic schedule of the film's production, Kubrick and Clarke had difficulty collaborating on the book. Clarke completed a draft of the novel at the end of 1964 with the plan to publish in 1965 in advance of the film's release in 1966. After many delays, the film was released in the spring of 1968, before the book was completed. The book was credited to Clarke alone. Clarke later complained that this had the effect of making the book into a novelisation, and that Kubrick had manipulated circumstances to downplay Clarke's authorship. For these and other reasons, the details of the story differ slightly from the book to the movie. The film contains little explanation for the events taking place. Clarke, though, wrote thorough explanations of "cause and effect" for the events in the novel. James Randi later recounted that upon seeing the premiere of 2001, Clarke left the theatre at the intermission in tears, after having watched an eleven-minute scene (which did not make it into general release) where an astronaut is doing nothing more than jogging inside the spaceship, which was Kubrick's idea of showing the audience how boring space travels could be. 
In 1972, Clarke published The Lost Worlds of 2001, which included his accounts of the production, and alternative versions of key scenes. The "special edition" of the novel A Space Odyssey (released in 1999) contains an introduction by Clarke in which he documents the events leading to the release of the novel and film.
2010: Odyssey Two Edit
In 1982, Clarke continued the 2001 epic with a sequel, 2010: Odyssey Two. This novel was also made into a film, 2010, directed by Peter Hyams for release in 1984. Because of the political environment in America in the 1980s, the film presents a Cold War theme, with the looming tensions of nuclear warfare not featured in the novel. The film was not considered to be as revolutionary or artistic as 2001, but the reviews were still positive.
Clarke's email correspondence with Hyams was published in 1984.  Titled The Odyssey File: The Making of 2010, and co-authored with Hyams, it illustrates his fascination with the then-pioneering medium of email and its use for them to communicate on an almost daily basis at the time of planning and production of the film while living on opposite sides of the world. The book also included Clarke's personal list of the best science-fiction films ever made.
Clarke appeared in the film, first as the man feeding the pigeons while Dr. Heywood Floyd is engaged in a conversation in front of the White House. Later, in the hospital scene with David Bowman's mother, an image of the cover of Time portrays Clarke as the American President and Kubrick as the Soviet Premier.
Rendezvous with Rama Edit
Clarke's award-winning novel Rendezvous with Rama (1973) was optioned for filmmaking in the early 21st century   but this motion picture was in "development hell" as of 2014 [update] . In the early 2000s, actor Morgan Freeman expressed his desire to produce a movie based on Rendezvous with Rama. After a drawn-out development process, which Freeman attributed to difficulties in getting financing, it appeared in 2003 that this project might be proceeding, but this was very dubious.  The film was to be produced by Freeman's production company, Revelations Entertainment, and David Fincher has been touted on Revelations' Rama web page as far back as 2001 as the film's director.  After years of no progress, Fincher stated in an interview in late 2007 (in which he also credited the novel as being influential on the films Alien and Star Trek: The Motion Picture) that he is still attached to helm.  Revelations indicated that Stel Pavlou had written the adaptation.
In late 2008, Fincher stated the movie is unlikely to be made. "It looks like it's not going to happen. There's no script and as you know, Morgan Freeman's not in the best of health right now. We've been trying to do it but it's probably not going to happen."  In 2010, though, the film was announced as still planned for future production and both Freeman and Fincher mentioned it as still needing a worthy script. 
Clarke published a number of nonfiction books with essays, speeches, addresses, etc. Several of his nonfiction books are composed of chapters that can stand on their own as separate essays.
Space travel Edit
In particular, Clarke was a populariser of the concept of space travel. In 1950, he wrote Interplanetary Flight, a book outlining the basics of space flight for laymen. Later books about space travel included The Exploration of Space (1951), The Challenge of the Spaceship (1959), Voices from the Sky (1965), The Promise of Space (1968, rev. ed. 1970), and Report on Planet Three (1972) along with many others.
His books on space travel usually included chapters about other aspects of science and technology, such as computers and bioengineering. He predicted telecommunication satellites (albeit serviced by astronauts in space suits, who would replace the satellite's vacuum tubes as they burned out). 
His many predictions culminated in 1958 when he began a series of magazine essays which eventually became Profiles of the Future, published in book form in 1962.  A timetable  up to the year 2100 describes inventions and ideas including such things as a "global library" for 2005. The same work also contained "Clarke's First Law" and text that became Clarke's three laws in later editions. 
In a 1959 essay, Clarke predicted global satellite TV broadcasts that would cross national boundaries indiscriminately and would bring hundreds of channels available anywhere in the world. He also envisioned a "personal transceiver, so small and compact that every man carries one". He wrote: "the time will come when we will be able to call a person anywhere on Earth merely by dialing a number." Such a device would also, in Clarke's vision, include means for global positioning so "no one need ever again be lost." Later, in Profiles of the Future, he predicted the advent of such a device taking place in the mid-1980s. 
Clarke described a global computer network similar to the modern World Wide Web in a 1964 presentation for the BBC's Horizon programme, predicting that, by the 21st century, access to information and even physical tasks such as surgery could be accomplished remotely and instantaneously from anywhere in the world using internet and satellite communication. 
In a 1974 interview with the Australian Broadcasting Corporation, the interviewer asked Clarke how he believed the computer would change the future for the everyday person, and what life would be like in the year 2001. Clarke accurately predicted many things that became reality, including online banking, online shopping, and other now commonplace things. Responding to a question about how the interviewer's son's life would be different, Clarke responded: "He will have, in his own house, not a computer as big as this, [points to nearby computer], but at least, a console through which he can talk, through his friendly local computer and get all the information he needs, for his everyday life, like his bank statements, his theatre reservations, all the information you need in the course of living in our complex modern society, this will be in a compact form in his own house . and he will take it as much for granted as we take the telephone." 
An extensive selection of Clarke's essays and book chapters (from 1934 to 1998 110 pieces, 63 of them previously uncollected in his books) can be found in the book Greetings, Carbon-Based Bipeds! (2000), together with a new introduction and many prefatory notes. Another collection of essays, all previously collected, is By Space Possessed (1993). Clarke's technical papers, together with several essays and extensive autobiographical material, are collected in Ascent to Orbit: A Scientific Autobiography (1984).
Clarke contributed to the popularity of the idea that geostationary satellites would be ideal telecommunications relays. He first described this in a letter to the editor of Wireless World in February 1945  and elaborated on the concept in a paper titled Extra-Terrestrial Relays – Can Rocket Stations Give Worldwide Radio Coverage?, published in Wireless World in October 1945.  The geostationary orbit is now sometimes known as the Clarke Orbit or the Clarke Belt in his honour.   
It is not clear that this article was actually the inspiration for the modern telecommunications satellite. According to John R. Pierce, of Bell Labs, who was involved in the Echo satellite and Telstar projects, he gave a talk upon the subject in 1954 (published in 1955), using ideas that were "in the air", but was not aware of Clarke's article at the time.  In an interview given shortly before his death, Clarke was asked whether he had ever suspected that one day communications satellites would become so important he replied: "I'm often asked why I didn't try to patent the idea of a communications satellite. My answer is always, 'A patent is really a license to be sued.'" 
Though different from Clarke's idea of telecom relay, the idea of communicating via satellites in geostationary orbit itself had been described earlier. For example, the concept of geostationary satellites was described in Hermann Oberth's 1923 book Die Rakete zu den Planetenräumen (The Rocket into Interplanetary Space), and then the idea of radio communication by means of those satellites in Herman Potočnik's (written under the pseudonym Hermann Noordung) 1928 book Das Problem der Befahrung des Weltraums – der Raketen-Motor (The Problem of Space Travel – The Rocket Motor), sections: Providing for Long Distance Communications and Safety, [d] and (possibly referring to the idea of relaying messages via satellite, but not that three would be optimal) Observing and Researching the Earth's Surface, published in Berlin.  [e] Clarke acknowledged the earlier concept in his book Profiles of the Future. [f]
Clarke was an avid scuba diver and a member of the Underwater Explorers Club. In addition to writing, Clarke set up several diving-related ventures with his business partner Mike Wilson. In 1956, while scuba diving, Wilson and Clarke uncovered ruined masonry, architecture, and idol images of the sunken original Koneswaram temple – including carved columns with flower insignia, and stones in the form of elephant heads – spread on the shallow surrounding seabed.   Other discoveries included Chola bronzes from the original shrine, and these discoveries were described in Clarke's 1957 book The Reefs of Taprobane. 
In 1961, while filming off Great Basses Reef, Wilson found a wreck and retrieved silver coins. Plans to dive on the wreck the following year were stopped when Clarke developed paralysis, ultimately diagnosed as polio. A year later, Clarke observed the salvage from the shore and the surface. The ship, ultimately identified as belonging to the Mughal Emperor, Aurangzeb, yielded fused bags of silver rupees, cannon, and other artefacts, carefully documented, became the basis for The Treasure of the Great Reef.   Living in Sri Lanka and learning its history also inspired the backdrop for his novel The Fountains of Paradise in which he described a space elevator. This, he believed, would make rocket-based access to space obsolete, and more than geostationary satellites, would ultimately be his scientific legacy.  In 2008, he said in an interview with IEEE Spectrum, "maybe in a generation or so the space elevator will be considered equally important" as the geostationary satellite, which was his most important technological contribution. 
Themes of religion and spirituality appear in much of Clarke's writing. He said: "Any path to knowledge is a path to God – or Reality, whichever word one prefers to use."  He described himself as "fascinated by the concept of God". J. B. S. Haldane, near the end of his life, suggested in a personal letter to Clarke that Clarke should receive a prize in theology for being one of the few people to write anything new on the subject, and went on to say that if Clarke's writings had not contained multiple contradictory theological views, he might have been a menace.  When he entered the Royal Air Force, Clarke insisted that his dog tags be marked "pantheist" rather than the default, Church of England,  and in a 1991 essay entitled "Credo", described himself as a logical positivist from the age of 10.  In 2000, Clarke told the Sri Lankan newspaper, The Island, "I don't believe in God or an afterlife,"  and he identified himself as an atheist.  He was honoured as a Humanist Laureate in the International Academy of Humanism.  He has also described himself as a "crypto-Buddhist", insisting Buddhism is not a religion.  He displayed little interest about religion early in his life, for example, only discovering a few months after marrying that his wife had strong Presbyterian beliefs.
A famous quotation of Clarke's is often cited: "One of the great tragedies of mankind is that morality has been hijacked by religion."  He was quoted in Popular Science in 2004 as saying of religion: "Most malevolent and persistent of all mind viruses. We should get rid of it as quick as we can."  In a three-day "dialogue on man and his world" with Alan Watts, Clarke said he was biased against religion and could not forgive religions for what he perceived as their inability to prevent atrocities and wars over time.  In his introduction to the penultimate episode of Mysterious World, entitled "Strange Skies", Clarke said: "I sometimes think that the universe is a machine designed for the perpetual astonishment of astronomers," reflecting the dialogue of the episode, in which he stated this concept more broadly, referring to "mankind". Near the very end of that same episode, the last segment of which covered the Star of Bethlehem, he said his favourite theory  was that it might be a pulsar. Given that pulsars were discovered in the interval between his writing the short story, "The Star" (1955), and making Mysterious World (1980), and given the more recent discovery of pulsar PSR B1913+16, he said: "How romantic, if even now, we can hear the dying voice of a star, which heralded the Christian era." 
Despite his atheism, themes of deism are a common feature within Clarke's work.  
Clarke left written instructions for a funeral: "Absolutely no religious rites of any kind, relating to any religious faith, should be associated with my funeral." 
Regarding freedom of information Clarke believed, "In the struggle for freedom of information, technology, not politics, will be the ultimate decider." 
Clarke also wrote, "It is not easy to see how the more extreme forms of nationalism can long survive when men have seen the Earth in its true perspective as a single small globe against the stars."  Clarke opposed claims of sovereignty over space stating "There is hopeful symbolism in the fact that flags do not wave in a vacuum." 
Clarke was an anti-capitalist, stating that he did not fear automation because, "the goal of the future is full unemployment, so we can play. That's why we have to destroy the present politico-economic system." 
Regarding human jobs being replaced by robots, Clarke said: "Any teacher that can be replaced by a machine should be!" 
Clarke supported the use of renewable energy, saying: "I would like to see us kick our current addiction to oil, and adopt clean energy sources . Climate change has now added a new sense of urgency. Our civilisation depends on energy, but we can't allow oil and coal to slowly bake our planet." 
Intelligent life Edit
Clarke believed, "The best proof that there's intelligent life in outer space is the fact that it hasn't come here . the fact that we have not yet found the slightest evidence for life – much less intelligence – beyond this Earth does not surprise or disappoint me in the least. Our technology must still be laughably primitive we may well be like jungle savages listening for the throbbing of tom-toms, while the ether around them carries more words per second than they could utter in a lifetime."  He also believed, "Two possibilities exist: either we are alone in the Universe or we are not. Both are equally terrifying." 
Paranormal phenomena Edit
Early in his career, Clarke had a fascination with the paranormal and said it was part of the inspiration for his novel Childhood's End. Citing the numerous promising paranormal claims that were later shown to be fraudulent, Clarke described his earlier openness to the paranormal having turned to being "an almost total sceptic" by the time of his 1992 biography.  Similarly, in the prologue to the 1990 Del Rey edition of Childhood's End, he writes ". after . researching my Mysterious World and Strange Powers programmes, I am an almost total skeptic. I have seen far too many claims dissolve into thin air, far too many demonstrations exposed as fakes. It has been a long, and sometimes embarrassing, learning process."  During interviews, both in 1993 and 2004–2005, he stated that he did not believe in reincarnation, saying there was no mechanism to make it possible, though "I'm always paraphrasing J. B. S. Haldane: 'The universe is not only stranger than we imagine, it's stranger than we can imagine.'"   He described the idea of reincarnation as fascinating, but favoured a finite existence. 
Clarke was known for hosting several television series investigating the unusual: Arthur C. Clarke's Mysterious World (1980), Arthur C. Clarke's World of Strange Power] (1985), and Arthur C. Clarke's Mysterious Universe (1994). Topics examined ranged from ancient, man-made artifacts with obscure origins (e.g., the Nazca lines or Stonehenge), to cryptids (purported animals unknown to science), or obsolete scientific theories that came to have alternate explanations (e.g., Martian canals).
In Arthur C. Clarke's Mysterious World, he describes three kinds of "mysteries":
- Mysteries of the First Kind: Something that was once utterly baffling but is now completely understood, e.g. a rainbow.
- Mysteries of the Second Kind: Something that is currently not fully understood and can be in the future.
- Mysteries of the Third Kind: Something of which we have no understanding. 
Clarke's programs on unusual phenomena were parodied in a 1982 episode of the comedy series The Goodies, in which his show is cancelled after it is claimed that he does not exist.
Clarke's work is marked by an optimistic view of science empowering mankind's exploration of the Solar System and the world's oceans. His images of the future often feature a Utopian setting with highly developed technology, ecology, and society, based on the author's ideals.  His early published stories usually featured the extrapolation of a technological innovation or scientific breakthrough into the underlying decadence of his own society.
A recurring theme in Clarke's works is the notion that the evolution of an intelligent species would eventually make them something close to gods. This was explored in his 1953 novel Childhood's End and briefly touched upon in his novel Imperial Earth. This idea of transcendence through evolution seems to have been influenced by Olaf Stapledon, who wrote a number of books dealing with this theme. Clarke has said of Stapledon's 1930 book Last and First Men that "No other book had a greater influence on my life . [It] and its successor Star Maker (1937) are the twin summits of [Stapledon's] literary career." 
Clarke was also well known as an admirer of Irish fantasy writer Lord Dunsany, also having corresponded with him until Dunsany's death in 1957. He described Dunsany as "one of the greatest writers of the century." 
Clarke won the 1963 Stuart Ballantine Medal from the Franklin Institute for the concept of satellite communications,   and other honours.  He won more than a dozen annual literary awards for particular works of science fiction. 
- In 1956, Clarke won a Hugo Award for his short story, "The Star". 
- Clarke won the UNESCO–Kalinga Prize for the Popularization of Science in 1961. 
- He won the Stuart Ballantine Medal in 1963. 
- Shared a 1969 Academy Award nomination with Stanley Kubrick in the category Best Writing, Story and Screenplay – Written Directly for the Screen for 2001: A Space Odyssey.
- The fame of 2001 was enough for the Command Module of the Apollo 13 craft to be named "Odyssey". 
- Clarke won the Nebula (1973) for his novella, "A Meeting with Medusa".
- Clarke won both the Nebula (1973)  and Hugo (1974)  awards for his novel, Rendezvous with Rama.
- Clarke won both the Nebula (1979)  and Hugo (1980)  awards for his novel, The Fountains of Paradise.
- In 1982, he won the Marconi Prize for innovation in communications and remote sensing in space. 
- In 1985 the Science Fiction Writers of America named him its 7th SFWA Grand Master. 
- In 1986, he was elected to the National Academy of EngineeringFor conception of geosynchronous communications satellites, and for other contributions to the use and understanding of space
- In 1988, he was awarded an Honorary Degree (Doctor of Letters) by the University of Bath. 
- Readers of the British monthly Interzone voted him the all-time second best science fiction author in 1988–1989. 
- He received a CBE in 1989,  and was knighted in 2000.  Clarke's health did not allow him to travel to London to receive the latter honour personally from the Queen, so the United Kingdom's High Commissioner to Sri Lanka invested him as a Knight Bachelor at a ceremony in Colombo. 
- In 1994, Clarke was nominated for a Nobel Peace Prize by law professor Glenn Reynolds. 
- The Science Fiction and Fantasy Hall of Fame inducted Clarke in 1997, its second class of two deceased and two living persons. Among the living, Clarke and Andre Norton followed A. E. van Vogt and Jack Williamson. 
- In 2000, he was named a Distinguished Supporter of the British Humanist Association. 
- The 2001 Mars Odyssey orbiter is named in honour of Clarke's works.
- In 2003, Clarke was awarded the Telluride Tech Festival Award of Technology, where he appeared on stage via a 3-D hologram with a group of old friends including Jill Tarter, Neil Armstrong, Lewis Branscomb, Charles Townes, Freeman Dyson, Bruce Murray, and Scott Brown.
- In 2004, Clarke won the Heinlein Award for outstanding achievement in hard or science-oriented science fiction. 
- On 14 November 2005 Sri Lanka awarded Clarke its highest civilian award, the Sri Lankabhimanya(The Pride of Sri Lanka), for his contributions to science and technology and his commitment to his adopted country. 
- Clarke was the Honorary Board Chair of the Institute for Cooperation in Space, founded by Carol Rosin, and served on the Board of Governors of the National Space Society, a space advocacy organisation founded by Wernher von Braun.
Named after Clarke Edit
In 1986, Clarke provided a grant to fund the prize money (initially £1,000) for the Arthur C. Clarke Award for the best science fiction novel published in the United Kingdom in the previous year. In 2001 the prize was increased to £2001, and its value now matches the year (e.g., £2005 in 2005).
In 2005 he lent his name to the inaugural Sir Arthur Clarke Awards – dubbed the "Space Oscars". His brother attended the awards ceremony, and presented an award specially chosen by Arthur (and not by the panel of judges who chose the other awards) to the British Interplanetary Society.
- Starting with Phase 1 of ESO Period 105 (Sept 2019), we introduce a new constraint, the atmospheric turbulence constraint. This constraint generalizes the classical seeing constraint used so far, and takes into account the coherence time and the fraction of turbulence in the ground layer, for instruments that need it, in addition to the classical seeing. These additions are important constraints for instruments using adaptive optics (AO) and need to be taken into account when scheduling observations to ensure that the science goals can be achieved. In order to harmonize this new scheme between all non-AO and AO instruments, a single Turbulence Category is introduced at Phase 1 for all instruments.