Astronomy

Brightness, altitude & azimuth for satellites?

Brightness, altitude & azimuth for satellites?


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I'm using the heavens-above website to identify a satellite I've seen several nights this week.

The question is related to how I can search the satellites table with the information I can provide.

The page has a table that has the satellite name,Brightness (mag), and Time, Altitude, and Azimuth forStart,Highest pointandEnd. I don't know how brightness and altitude are measured, and I don't know how the start, highest, and end points are measured. In terms of azimuth, if I base it on this compass, and based on the time I saw it, I would have to say NNE.

With that said, last night I was sitting looking straight north. I first saw the satellite, literally moving directly over my head, at 7:33pm EST and stopped seeing it at a 7:36PM EST because it was too far. The satellite was going North and just a bit to the East.

My question: how can I use this information to search for the satellite in the table? Also, how do I know what's the Brightness (mag)? The satellite is so tiny that it's almost impossible to see with the naked eye.


Altitude is measured in degrees above the horizon, from 0° on the horizon to 90° directly overhead. Your fist appears about 10° wide at arm's length away from your eye.

Azimuth is measured along the horizon, usually with north 0°, east 90°, south 180° west 270°, and other directions (e.g. NNE, ENE) interpolated as in the compass image.

Magnitude is a logarithmic scale in which the brightest stars are 0 or 1, and the faintest stars visible to the unaided eye are 4 or 5 (maybe 2 or 3 in a city, or 6 in a remote area).

Each row of Heavens-Above's table links to a sky chart showing their predicted path for that satellite pass. The brightness listed in the main table is a maximum; the table under the sky chart shows a brightness for other points on the path.


Thread: PROTRACTORS FOR MEASURING DEGREES IN SKY

Ok folks, here are a couple of printable protractors and an astrolabe.

You can use these for finding satellites, iridium flares, and other neat things in the sky.

The first one you can used for finding angles off the horizon.

Aim the base of the protractor level with the ground you are standing on, and then 90 degrees is straight up. With this you can tell what 10 degrees, 20 degrees, etc. are above the horizon. 90 degrees is directly overhead. You can copy this image to a Word program to enlarge or reduce the size of it.

Here is a 360 degree protractor. You can use it for the same thing, but you can also use it for finding Azimuth directions around the globe. Place the paper flat with the ground you are standing on, then aim the inner 𔄘” to the North and read the inner circle of numbers. 180 degrees on the inner circle will aim South. 90 degrees will be East. 270 degrees will be West. Copy the image to Word program document to enlarge or reduce the size.


Astronomy Software

This astronomy software page contains links to sites with PC software of interest to the astronomy hobbyist. These programs include useful astronomy utilities and programs that are educational and fun. Some of this software is free and some is commercial or shareware. There are also a few demo versions of some commercial software products.

Each entry contains a description of the software type as well as the last known price. Please read the information on each publisher's site for more detailed information. These astronomy software links are provided for informational purposes only. Sea and Sky does not endorse these products.

Free Astronomy Software

Astroviewer
Platform: Windows 98 and above Cost: Free Demo: Download available
AstroViewer is a planetarium software that helps you to find your way in the night sky quickly and easily. Due to its intuitive and easy-to-use graphical user interface, it fits well to the demands of astronomy beginners.

Celestia
Platform: Windows, Linux, Mac OS X Cost: Free Demo: N/A
Celestia is a very unique 3-dimensional universe simulator. With it you can travel throughout the Solar System, to any of over 100,000 stars, or even beyond the galaxy. Celestia comes with a large catalog of stars, planets, moons, asteroids, comets, and spacecraft. If that's not enough, you can download dozens of easy to install add-ons with more objects. The program is highly configurable and expandable. A library of add-ons and expansions is available including everything from additional stars & galaxies to science fiction worlds and spacecraft. For those with fast processors, you can even download and install super high resolution images of the planets and moons enabling you to zoom in close and explore every subtle detail. You can even take screen shots of your favorite scenes. Celestia is highly recommended by Sea and Sky!

Home Planet
Platform: Windows 95 and above Cost: Free Demo: N/A
Home Planet is a comprehensive astronomy, space, and satellite-tracking package for Microsoft Windows 95 and Windows NT 4.0 and above. Features include an Earth map showing day and night regions, position of selected satellites, positions of the planets, positions and phases of the Sun and Moon, sky map based on either the Yale Bright Star Catalogue or the 256,000 star SAO catalogue, including rendering of spectral types, planets, Earth satellites, asteroids and comets, and much more.

Stella 2000
Platform: Windows 95 and above Cost: Free Demo: N/A
Complete astronomy software suite exploring realistic skies in real time, with observing log, Sky Quiz, Live Orbits, telescope support, spoken pronunciation guide, a half-million word Encyclopedia Astronomica, and concentrated searches embracing planets, comets, asteroids, DSOs, and over 300,000 stars. An integral HTML guide to the solar system, a 1000-term astronomical dictionary, and the 2nd revised and enlarged edition of Aspects of Astronomy--a book-length primer covering topics such as "What are the Stars?", "Choosing a Telescope", "Cosmology", "Dark Matter", "Eclipses", and "The History of Astronomy", to name but a few--are closely coordinated with the sky display and picture windows.

Stellarium
Platform: Windows, Linux, Mac OS X Cost: Free Demo: N/A
Stellarium is a free GPL software program which renders realistic skies in real time with openGL. It is available for Linux/Unix, Windows and MacOSX. With Stellarium, you really see what you can see with your eyes, binoculars or a small telescope. Loaded with advanced features, this incredible software will turn your PC into a virtual planetarium! This is definitely one of the best free astronomy programs currently available for download. Stellarium is highly recommended by Sea and Sky!

WinOrbit
Platform: Windows 3.1 or later Cost: Free Demo: N/A
WinOrbit is a free software package for Microsoft Windows (3.1 or later), which will compute and display the position of artificial Earth satellites. The principal feature of WinOrbit is a series of Map Windows, which display the current position of satellites and observers on a simple world map, together with information such as bearing (azimuth), distance, and elevation above the observer's horizon. The maps can be updated in real time, or in simulated time, or manually set to show the situation at any time past or future. An additional Table Window displays much more-detailed information about one or more satellites in a tabular form.

Astronomy Shareware

Cybersky
Platform: Windows XP and above Cost: $34.95 Demo: 30-day trial download available
CyberSky is an exciting, entertaining, and educational astronomy program that transforms your personal computer into your personal planetarium. CyberSky provides an excellent way to learn about astronomy and to explore the wonders of the sky visible in the distant past, the present, and the far-off future. CyberSky displays accurate charts of the sky as seen from any location on the Earth. Sky charts can include stars, constellations, deep sky objects, and solar system objects, and can be enhanced by the addition of labels, coordinate system grids, and reference lines. CyberSky's user-friendly interface allows you to easily change your view of the sky, search for celestial objects, and display data about those objects. CyberSky also prints attractive sky charts that you can take outside with you.

StarStrider
Platform: Windows XP and above Cost: $22.00 Demo: 30-day trial download available
StarStrider is a three-dimensional star plotting program that allows the user to see the stars and constellations from distant points in the sky. With the help of StarStrider you will be able to travel to the stars and watch their alien skies. Travel to Vega and see how the Sun pales to a faint star, a star among thousands of others. Look at the Pleiades from behind! With ordinary red/blue 3D glasses your experience will be even greater. Now you can see the variable distances to the stars - without even leaving our solar system if you don't want to! Cassiopeia looks really different when you realize that the constellation aren't flat. You'll also learn to appreciate the fact that the closest stars are not always the brightest.

Commercial Astronomy Software

MegaStar Sky Atlas
Platform: Windows 95 and above Cost: $129.95 Demo: N/A
MegaStar is the first software to integrate the Hubble Guide Star Catalog, and combine it with a massive deep sky database of 84,000 objects. It is also the first to implement the "eyepiece view," with deep sky objects plotted to scale and galaxies rotated to show position angle. This is an extremely detailed visual sky atlas program with too many features to mention here. Check out their site for more information. A demo version of the software is available for download.

Starry Night
Platform: Windows XP & above, Mac OS X 10.4 & above Cost: $24.95 - $239.95 Demo: N/A
Starry Night is the most visually stunning and realistic astronomy program in its class. A powerful tool for both serious observers and casual stargazers, Starry Night lets you view the universe from anywhere in the Solar System. Explore over 19 million celestial objects and travel across 14,700 years of night skies. Features include a 19 million object Hubble Guide Star catalog and the ability to add new objects and databases. An evaluation version of the Basic version is available for download.


Observing Satellites

Is there a good thread dedicated to observing satellites anyone can point me to?

What tips or extra equipment (if any) is needed.
I'm trying to get my head around

c) the speeds and directions involved.

#2 jgraham

"Is there a good thread dedicated to observing satellites anyone can point me to?"

Not that I have seen, but the forum on solar system observing might be a place to look.

Long ago I wrote my own software for predicting the particulars of satellite overflights, altitude and azimuth versus time, but there are now software packages and apps that do a nice job.You might also look at Dr. T.S. Kelso's CelesTrak web site.

This is very easy to do once you know when and where to look. You can use anything from just your eyes to binoculars or a small telescope. For many years I used this little scope made from an old photocopier lens.

. note the altitude and azimuth marks on the mount. I now use a StarBlast fitted with altitude and azimuth circles.

The idea is to generate a list of targets (hundreds each night) and to point the scope at the designated altitude and azimuth shortly before the predicted time and wait for a little point of light to enter the field. If it doesn't, move ahead to the next predicted location and try again. Once you spot it, the chase is on! They can move at a pretty good clip (you get a feel for how FAST they are moving) so you need a nimble, wide field scope to follow them.

c) the speeds and directions involved.

Usually west-to-east, but they can also move either way north/south. Geosynchronous satellites move very slowly north/south, geostationary satellite don't move at all, but can vary in brightness.

Edited by jgraham, 28 November 2016 - 10:59 AM.

#3 jimr2

For finding satellites passing over your area on any given date, you can check the Heavens-Above site (www.heavens-above.com). Input your location, what satellites(s) you're interested in checking on, and it will display a list of all (or visible passes only) for the next week or so.

#4 t_image

Take a 3D tour with an amazing website: (tour described below to orient you to the information the site provides and is a quick lesson on types of satellite orbits!)

Orientation of website model:
search feature on left. Type in a group name of satellites or specific object and their orbits/its orbit will be highlighted in the model, while listing in text all members of the group in order of Int'l designator (also launch sequence).
Zoom in or out with mouse wheel or +/- on right of screen.

click and drag to reorient the "camera" to show what side of the Earth:

*Note the dark side of the Earth land masses will only show lights, the lit side of the Earth will show visible land masses.

Click on dot to highlight its orbit ring and details given in window on right.
Notice the realtime data given of the object when click on:
Int'l Designator (which is the year of launch, then the number sequenced based on what order in the year the object was launched).
Type:same as color code:

payload (red) is the object designed to orbit for its particular function

rocket body (blue)-final stage of rocket that placed payload in orbit, stayed in orbit

debris (gray) rocket bits from launch or bits of satellite
Apogee/Perigee -static measurement that describes the orbit -the closer they are to equal means the more circular the orbit
Inclination-the angle of orbit compared to how parallel with the Earth's equator
Altitude the direct distance from object straight down to the closest surface on Earth
Velocity-angular speed of object around the Earth
Period-amount of time it takes to complete an orbit (full track around Earth)

Take My Tour of the different Orbit Types with representative objects:
1. Scroll out far out, note the interesting distribution patterns [we'll get to more detail in a second].

2. Scroll in close to the Earth with mouse wheel to notice dark (nightime) and daytime parts of Earth, note Poles and Equator location.

3. scroll way out. over on the left search feature type the word "Intelsat"

  • notice all of the sudden a bunch of blue orbits are highlighted and a list of intelsat satellites are listed downward from the search bar.
  • notice if you hover over the text names, the specific orbit is highlighted and labeled in the 3D model.
  • notice if you click on the the name, it will color that orbit in green and move you closer and show the dot of the object selected.
    • Notice the intelsats are mostly in a predictable 3D ring around the Earth, all above the Equator and at altitudes of 35,000km.
    • They have varied inclinations but mostly from 0-15 degees of variance from orbiting parallel with the Earth's equator.
    • They mostly have a velocity of

    These are a network of Geostationary communication satellites and pretty much stay immediately above the same spot on Earth.
    So the satellite dish doesn't need to move.
    The maneuvers necessary to keep the objects stationary above the same spot is called "station keeping."

    click on black space and zoom out to continue.
    4. clear the search and type: "iridium"

    • notice the blue orbits now highlighted and the text list of names of iridium objects.
    • notice the Iridium satellites orbits are all perpendicular to the equator (Inclination=

    LEOs are usually the ones that you can see moving as points of light across the sky.

    Iridiums are a constellation of communication satellites that move across a fixed path and with many, the entire Earth can be always covered so the satellite phones depending on them can be used anywhere in the world.

    Iridiums are also unique in that their construction afforded long shiny antennas that allow the Sun, in the right place and right time, to reflect towards an observer with such change in brightness as to appear for a few moments as a "flare" sometimes even to magnitude 8. -many of these events are predictable with math, but it has to be calculated based on the observer's coordinates.

    click on black space and zoom out to continue.

    5. clear the search and type in "O3B".

    • notice there are 12 text names and they all share the same blue orbit path.
    • notice they are spaced out red dots along the highlighted blue orbit.
      • notice the Inclination=

      The O3B network is a constellation of communication satellites that move slowly and the satellite dishes that track them also move.

      click on black space and zoom out to continue.

      6. clear the search area and type in "molniya"

        notice a list and all the interesting blue orbits highlighted.
          notice they all share Inclination=

        40,000km and the Perigee is

        These are a series of communication satellites used to both benefit areas of the Earth that are more polar, while needing less number of satellites (compared with Iridium network) to maintain point-point communication.
        The funky orbit shape is therefore named "Molniya-like" after these objects, and the utility of this type of orbit is used with a number of craft for different purposes.

        click on black space and zoom out to continue.

        7. clear the search area and type in "yaogan 9"

        • notice there are 3 of them A,B,C, if you click on the text to highlight the orbit in green and move to where they are located, they are oriented in a triangle and move together
        • notice they are also LEO satellites
        • if you look them up and find visible passes (fainter) you will see all three of them in the sky in triangle formation.

        These are Chinese objects for scientific or military purposes.

        click on black space and zoom out to continue.

        zoom and click and drag around the orbits zoomed out.
        >Now you can spot the GEOsat area that is a narrow column of dots over the equator and you know what that is about!
        >Now you can spot the inner sphere of objects in LEO easily and know these are the ones you will probably be able to see moving across the sky!
        >Now consider all the other objects randomly distributed, especially the blue ones, rocket bodies that are in graveyard orbits stuck in space for the moment and orbiting in ways that hopefully keep them out of the way of the payloads, since they are empty shells and can't be controlled.

        You can move your mouse to slowly hover over certain dots-which will label the object and its orbit. Investigate further all the different types.

        Of course, you can go to the search and type in "ISS" (ZARYA) will be the space station. check out its orbit and where it currently is located above the Earth.

        Notice in the about section the data about each object is updated daily from space-trak, a service of the USAF-USSPACECOM that updates the math of the objects.
        Each object has a Two Line Elements-two sets of numbers that describe the math of the orbit.
        With these numbers, software can:

        • plot the location of the object are a certain point in time
        • predict whether it will be above the horizon of a given observer based on observer's coordinates
        • and while including math on the location and level of the Sun below the horizon, the software will also predict whether the objects above the observer's horizon will be in Sunlight (while observer is experiencing night) and therefore will reflect Sunlight and be visible as points of light moving across the sky.

        Each object has a normal "brightness" value based on its size, reflective bits, and distance from the Earth, and the software can also tend to predict how bright the object may appear during a visible pass.

        Appearance of satellites:

        So now that you have an overview of the many bits in orbit, let's consider more of what they might look like from the ground.

        Given the orientation of the satellite/object, where the Sun is currently, and the coordinates of the observer,

        • an orbiting might pass overhead in complete shadow during the night because the Sun is lower behind the Earth relative to the object. Most do.
        • Others may be in sunlight but so far away as to be very dim and only show up in long exposure photographs.
        • An orbiting object might also pass overhead in such a way as to come out of shadow and enter Sunlight (while observer in dark) and thus appear as a point of light out of nowhere, and trace across the sky as a point of light.
        • Objects may also pass overhead in such a way as to be in sunlight for the moment (while observer in darkness) and appear as a point of light moving across, then suddenly enter into shadow, and thus appear to fade out while high in the sky.
        • Others will trace across the sky as points of light from horizon to horizon, and the lower the altitude the object, the more likely it will only be visible close after Sunset or just before Sunrise (Summer allows objects to be seen deeper into the night due to Sun's more shallow angle-mid latitudes).

        Apparent Speed across the sky:

        • Note apparent speed as an orbiting object appears to move across the sky as a point of light is affected by two things:
          • the closer in altitude, the faster it will appear to move across,
          • the higher above your head (towards Zenith) the faster the object will appear to move because the distance from observer to object is cut due to direct angle, as opposed to being near the horizon, which means the object is much further away from the observer than if it were overhead--and since it appears further away, it will appear to travel slower

          [this is the same effect observed with planes in the sky-however with orbiting objects the extremes of the effect is greater because they are so much more distant. ]

          Looking at a sky plot of an orbiting object over-the-horizon visible pass on a site like heavens-above that shows tick marks of where the object will be at what minute, illustrates this phenomenon (slower at horizon, faster as goes across higher in sky).

          Besides flare events like Iridiums can be known to do, other times an orbiting object may tumble or rotate [usually those that aren't functioning] in a way that "flashes" or glints either in a predictable period or randomly glints.


          Spectrophotometry

          Carol J. Bruegge , . Felix C. Seidel , in Experimental Methods in the Physical Sciences , 2014

          12.3.7 Cloud Altitude

          While cloud altitude is often estimated by using measured brightness temperature or by CO 2 slicing [26] , this is an indirect approach that also needs knowledge about the atmospheric temperature structure to relate temperature or pressure to height. Direct measurement can of course be made using space-borne lidar [27] , but cloud heights can also be measured directly using measurements of reflected solar radiance—provided these are made at reasonably high spatial resolution simultaneously from at least two directions. This approach takes advantage of the fact that most clouds are not plane parallel giving rise to spatial contrast patterns of reflectivity at cloud top that can be matched from two directions. The resulting parallax provides a stereo estimate of cloud-top height that is independent of the atmospheric temperature structure, and that is insensitive to radiometric calibration. In the case of MISR, for example, the effective, global, annual cloud-top height can be measured to within a sampling error of about 8 m [28] .


          Comments

          December 3, 2019 at 5:28 pm

          This issue is only going to effect the night sky during astronomical twilight and not later. These satellites will then be in earth's shadow since they are at a much lower altitude. No one in the astronomy community seems to be mentioning this. Remember over 3 billion people have no access to the internet and 5 BILLION do not have 25mbs that the major cities in the USA have. We forget how small (5%) a country the USA is when compared to the rest of the world's population.

          You must be logged in to post a comment.

          December 3, 2019 at 8:01 pm

          Hi Mike, that's a great point, and one that I address in the feature. How far into the night a satellite is visible depends on its altitude as well as on the observer's latitude. The megaconstellations being proposed are at a wide variety of altitudes in low-Earth orbit. Lower altitudes mean brighter satellites, but they're also visible for less of the night satellites in higher-altitude orbits will be fainter but visible for more of the night. And latitude matters: At high latitudes in summertime, satellites will actually remain visible for most of the night. Cees Bassa has tweeted some visualizations of satellite visibility (such as the one here: https://twitter.com/cgbassa/status/1132551806125522945) and we feature his work in the feature as well.

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          December 4, 2019 at 4:19 pm

          I was imaging M42 a couple of nights back here in the UK, offset to try and catch the NGC1999 in the frame, and every single exposure (20s to 180s) showed at least 3 Starlink satellites passing below NGC1999. The magnitude varied slightly, the track varied slightly, but they kept coming throughout the hour I was imaging that area. Watching the track the satellites were taking, I gave up, and sure enough processing the stacked images did not remove the trails, as some seem to be on exactly the same track. This was 22:00 - 23:00 at 52N - the sun had disappeared below the horizon 4-5 hours earlier and, when I gave up, was due up in 6 hours. if the satellites are visible to imaging at 23:00 in the winter, they are going to be visible to imaging all night long, all year round, until they get to the operating altitude.. maybe even then.

          As for the 3 billion people who do not have access to the internet, the majority of those also don't have access to electricity and/or the minimal wealth to afford Elon's terminals, unless he plans to give them away?

          You must be logged in to post a comment.

          December 6, 2019 at 8:32 pm

          Your point is well taken regarding access to the Internet by humanity is agreed, but isn't there perhaps a better engineering solution to the problem that does not damage the environment or our ability to explore the Universe?
          Doesn't Starlink design and deployment mostly based on reducing the commercial costs and making profit rather than human need to observe the sky? Is there a better and less damaging way to achieve this aim?
          Also saying "We forget how small (5%) a country the USA is when compared to the rest of the world’s population." is a plain contradiction, as the full deployment will affect 100% of the world's population. e,g. So 95% of the population have no say in their own desire to observe the Universe?
          Total investment in ground-based astronomy is significant for many countries, being a global undertaking toward uniting our human desire of exploration and collaboration without the weight of commercial gain or nationalistic competition. e.g. Pure science. Astronomy is one of the the final bastions that hasn't been totally destroyed by vested interests. Sacrificing this might be an awfully high price that we may well rue for our future generations.
          IMO astronomical endeavours must be defended and protected at all cost.

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          December 3, 2019 at 6:07 pm

          Do we want to have a window onto the rest of the universe, or a mirror reflecting back tweets and HD videos onto every square centimeter of the Earth's surface? It's too bad we need to rely on the good will of an unlimited number of unregulated high tech entrepreneurs. Even if most of them make every possible accommodation, the sheer number of satellites in multiple arrays will be problematic, and one or a few bad actors would have a huge negative effect.

          You must be logged in to post a comment.

          December 4, 2019 at 2:45 am

          I wonder what uncontacted tribes in places like Brazil are making of this.

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          December 4, 2019 at 6:20 am

          Nice to see a more thorough article, as well as the promise of more to come. The obvious question from outsiders (disclaimer: I do have an interest in astrobiology and so cosmology) is why the regulatory process, the satellite traffic oversight, and - it seems - the astronomical society - are all unprepared?

          The process seems mainly commercial/military though I gather radio astronomy has protected bands the satellite traffic oversight has reportedly no enforced avoidance procedures (so e.g. Starlink satellites will be self guided to avoid collisions and can go anywhere within the orbit corridor), and the astronomy society seems to have no weight or even communication insight whatsoever (s e.g. the launch trains are coming as surprises instead of as planned interrupts)..

          Hopefully the upcoming articles will go over some of that. The same reactive-instead-of-proactive process can be seen in regards commercial interplanetary traffic impact on astrobiology (e.g. the dead but still organic contaminants of stealth tardigrades on the Moon, adding to the Apollo waste bags).

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          December 5, 2019 at 12:55 am

          don't forget the impact on infra-red and radio astronomy. black paint won't work there.

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          December 6, 2019 at 7:27 pm

          The argument for this sadly falls back to imposing exploitation, politics and singular domestic national commercial interests - regardless of moral damage it may cause or the collective wishes of humanity or other nations. Worst the launching of all these satellites plainly ignores international agreements - the peaceful and specific non-commercial use of space. If saying : "For their first 1,584 satellites, SpaceX has FCC approval for 24 orbital planes of 66 satellites each." is true, then the problem is really down to the Federal Communications Commission (FCC) is a wholly US agency, whose goal is: "make available so far as possible, to all the people of the United States, without discrimination on the basis of race, color, religion, national origin, or sex, rapid, efficient, Nationwide, and world-wide wire and radio communication services with adequate facilities at reasonable charges." (Five elected US politicians.) Whilst this organisation may have an International Bureau (IB) for agreed telecommunications bandwidths, there is clearly no provision to protect the interests of other countries - nor now seemingly even their own rights to freely explore and observe the vast universe. The contradiction is plainly obvious. e.g. What is truly ironic here is Musk's SpaceX laudable goals of advancing the exploring or colonising the Moon or Mars but willingness to sacrifice the ability and philosophical need to understand humanity's place in the world.
          I personally find that the sheer degree of imposition of another country upon my own environment is quite repulsive and abhorrent. In my view, it is just another step towards the obliteration of our collective futures - as exhibited from such things as the dogmatic attitudes towards climate change or other unnecessary destructive human activities such as the ever continuing encroachment of light pollution.
          IMO, the cost of this Starlink (and future satellite constellation 'infestations') on astronomy is far too high a price.

          You must be logged in to post a comment.

          December 7, 2019 at 9:14 pm

          Even if it will be practical or even possible, who ruled that colonizing the Moon or Mars is a worth while or even moral laudable goal?

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          December 6, 2019 at 9:52 pm

          I’m glad they’re putting thought into reducing the satellites’ impact on the night sky. I wonder what effect, however, the black paint will have on the satellites’ ability to keep cool?

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          December 7, 2019 at 1:06 pm

          Are any other launch-capable countries planning similar exploits? If so, this could be just the tip of the iceberg (and just as destructive to astronomy as that one the Titanic encountered).

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          December 10, 2019 at 2:04 pm

          We have read in these pages recently of the negative effect of the relatively rapid switch from sodium vapor to bright-white LED streetlight and security illumination, and now the current debate over the Starlink situation. It all reminds me of something that Leslie Peltier once prophetically wrote over 50 years ago in Starlight Nights: " In these strange lights that cross the sky my two scopes see a gloomy portent, a distant early warning of the nights to come. Forty years ago, on the top of Mt. Wilson, the world's largest telescope could look down and see the gathering lights below. Today the approach is from above as well.

          So much that man touches he destroys."

          Monica, why was your article pulled so soon? I hope he hasn't gotten his fingers into S&T!!


          Satellite Tracking using Astronomy Goto Mount

          Recently, I reviewed the video by K4WOF https://www.youtube.com/watch?v=kpgV8P6ocLE and was motivated to build my own satellite tracking mount. Satellite operations are considerably easier if satellite tracking is automated so that satellite passes can be focused on radio work. Somewhat comically, automated antenna tracking looks exciting and generates community interest in our amateur radio activities. I have to apologize as mistakes were made by me as I came up to speed with satellite operations. A shout out to Jason N8PDX for invaluable feedback.

          As an amateur astronomer I have been working with “goto” telescope mounts for more than a decade – “Goto” computer controlled telescopes are designed to make night viewing easier by automatically moving the telescope to an object in the sky via computer control, and then the telescope mount can track the object for many hours. The more expensive goto telescope mounts can track objects for days with no tracking errors. With our busy lives and brief sky viewing opportunities, a “goto” telescope mount makes astronomy easy, and more complex activities such as long exposure astrophotography accessible to all. The inexpensive goto telescopes provide an easy path for new amateur astronomers as they take the guesswork out of finding objects in the night sky.

          Goto telescopes are made up of four components – The Tripod/leveling base, the telescope mount (with motors) for object tracking, the optical tube, and the computer controller. Initial setup requires a simple alignment procedure, but once aligned, tracking will remain accurate for many hours. All the consumer goto telescopes have a basic sky object database built in to a small handheld computer controller with provision for serial connectivity to an external computer for advanced software control. The Meade ETX60 and the Celestron Astro FI are two examples of consumer grade goto telescopes.

          Assembling PVC antenna mounting components.

          Telescope mounts come in two form factors – Equatorial (Eq) Mounts, and Altitude/Azimuth (Alt/Az) mounts – Equatorial mounts tend to be simpler and more accurate if only since once they are first orientated to your latitude, they only need to track an object in one plane. Alt/Az mount are leveled to your location, and thus for solar system and deep space objects, they will need to move in two axis to track objects. Either mount would need to move in two axis to acquire a satellite. My personal preference is to use an Alt/Az mount for satellite tracking.

          So, the important questions are “Can a goto telescope track satellites like planets, asteroids, or deep space objects?” The answer is maybe! “Can a goto telescope move quickly to a location in the sky?” The answer is absolutely yes! It’s the ability to move quickly from one location in the sky to another that makes goto telescope mounts useful to us for satellite work. To expand on this, certainly there are telescope mounts that can track satellites, but if we are also using VFO computer control, there is the need for coordination between two “computers” for each satellite pass. Selecting the satellite on the telescope mount, and selecting the satellite on the VFO control.

          As an FYI, the coordinate system used to track solar system and deep space objects is a different model than what is used to track satellite positions. Although many telescope mounts have the fine and fast motor control to follow a satellite, only a few telescope mounts have the ability to accept satellite TLE data. The Meade “goto” mounts have satellite tracking capabilities.

          The data a goto telescope mount uses for tracking objects.

          When a “goto” scope is commanded to move from one location in the sky to another, the scope will move quickly to the desired location – This action is called slew or slewing. For satellite tracking, we just need to “slew” every few seconds to accurately track satellites for the purposes of amateur radio communication. Depending on the telescope mount software and hardware capabilities, the position commands for this action will either be entered as Right Ascension/Declination (Ra/Dec) coordinates followed by a slew command, or via Elevation or Altitude/Azimuth (Alt/Az) coordinates followed by a slew command.

          Some goto telescope mounts will only accept Ra/Dec or Alt/Az while others will accept both formats. Equatorial telescope mounts commonly only accept Ra/Dec commands. There is a means to calculate Right Ascension and Declination from Altitude and Azimuth but to do so, you will also need your local Latitude, Longitude, and UTC Time.

          The astronomy community has been satellite tracking for some time the purpose of actually spotting satellites at sunrise and sunset with a telescope when the satellites are still illuminated by the sun – SkyTrack by http://www.heavenscape.com is an example of one such program and with this program alone, you have automated satellite tracking using various goto telescope mount manufacturers. SkyTrack uses an open source telescope mount API called ASCOM to communicate with a telescope mount which is supported by most astronomy manufacturers. What astronomy programs are missing is satellite frequencies and transceiver VFO control to compensate for doppler.

          I felt that there was a “fast path” to satellite tracking using a telescope mount. I believe the various Alt/Az one armed and fork mounts by Meade, Celestron, and iOptron well suited to the task. Portability is very important. I chose the iOptron Az Mount Pro as my platform with a number of advantages over other mounts with these features –

          • An Alt/Az mount with the ability to support Altitude and Azimuth commands.
          • Onboard battery so external power is optional.
          • 33lb primary dovetail interface with a secondary 11lb dovetail interface. A secondary allows a second telescope or antenna to be attached. A dovetail is a means of quickly attaching a telescope (or antenna).
          • A wifi interface so that command/control can be wireless.
          • Single star alignment.
          • Portable!

          Amateur radio satellite tracking programs have been optimized to work with more traditional “rotators” which unfortunately have fairly “cumbersome” I/O interfaces and large power requirements. Fortunately, these programs do output altitude (elevation) and azimuth data for rotators to action.

          Lets review the software options we have available to us for satellite tracking –

          1. Some satellite mounts support TLE input. Meade as an example, but with the challenge adapting the mount to antennas. The Meade LX65 mount looks to be ideal for amateur radio satellite operations.
          2. ASCOM compatible software – Astronomy software SkyTrack using the ASCOM API. SkyTrack will accept an amateur radio TLE database and interface with any goto telescope mount via ASCOM. This is a Windows Program. Radio VFO control would need to be performed manually or via an independent program.
          3. Hamlib compatible software – Hamlib is the “swiss army” knife of radio and rotator control includes VFO control of numerous radios together with support of rotators including telescopes. Radio software that has radio and rotator controls can take advantage of frequent updates to Hamlib that add new radio and rotators. Recently, the iOptron telescope mount was added to Hamlib adding to existing support of Meade and Celestron telescope mounts. Gpredict is one satellite tracking application that can leverage this support from Hamlib to both control VFO’s for satellite frequency and doppler adjustment and rotators including Telescope mounts for satellite tracking.
          4. Write Your Own Software – Many satellite tracking software applications will provide a basic means of outputting Altitude and Azimuth information. As an example, MacDoppler can output rotator control information to a UDP port. If you have programming skills, you can use standard API’s and interfaces to adapt to your own needs.

          I decided to pursue a “write my own” software for three reasons – (1) Take advantage of MacOS software MacDoppler and continue to use my Mac for portable operations, (2) take advantage of WIFI control of my goto telescope mount via TCP/IP simplifying data cabling between mount and computer. This means there is no interaction between me and the telescope mount during passes, and (3) The mount I am using have an incredibly simple alignment process as it has a built in GPS. It calculates its own position, aligns itself, then prompts you to fine tune alignment on a single bright object in the sky.

          My software consists of MacDoppler configured for my IC-9700 connected via USB cable for VFO control. The WIFI from my Mac is connected to my iOptron goto telescope mount and a Python script performs the following:

          • Opens the MacDoppler UDP port to receive Altitude and Azimuth information.
          • Opens a TCP port to the Telescope Mount
          • Formats the UDP Altitude and Azimuth information from MacDoppler into Telescope Mount commands a. Set Altitude, Set Azimuth, and Slew.
          • This occurs every 1 second and this frequency is more than accurate to maintain alignment.

          This Python script is available at https://github.com/djsincla/goto and can be modified relatively easily to change from TCP to serial port control of the Telescope Mount. The program also includes a module to calculate Right Ascension and Declination if the goto telescope mount does not support Altitude and Elevation.

          For antenna hardware, I chose the Arrow antennas phased at 90 degrees with phasing cables from Diamond for both 2M and 73cm connected to a diplexer so that a single antenna cable runs to the radio. Antennas are mounted to the goto telescope mount using standard Telescope dovetail plates together with some PVC pipe connectors. The iOptron Az Mount Pro I own is assembled the same as if I was going to mount a telescope. I just attach antennas instead.

          Initial attempts to consolidate cabling to the mount itself were ok but I felt to simplify, it was simpler for antenna cables to hang below the antennas. PVC is inexpensive so changes to mount configuration will likely be ongoing as I continue to tweak the configuration.

          iOptron AZ Mount Pro, Icom IC-9700 Transceiver, and MacDoppler software

          I am using the Icom IC-9700 as my portable rig and both radio and the iOptron telescope mount have their own Pelican cases making deployment fast. I power everything off an accessory battery in my van that has an Anderson Power Pole attached. Given the low Amp requirements of Satellite VHF/UHF operations, the van accessory battery has more than enough amp hours to cover extended sessions hunting satellites.

          Price – I want to be clear that I was not build for the most inexpensive setup as I am reusing the goto telescope mount I own for astronomy. The iOptron Az Mount Pro I own is a $1200 goto mount. Everything I have done can be reproduced on a less expensive mount and I will circle back around when I have everything dialed in and demonstrate on a

          $400 goto mount.
          Setup process is:

          • Set up tripod and telescope mount.
          • Attach antennas with phasing cables and diplexer
          • Perform telescope mount alignment
          • Connect diplexer to radio
          • Connect radio to USB computer
          • Start MacDoppler Software
          • Start Python Script

          Success? Yes!! Surprisingly good reception with only 10-15+ degree elevation as satellites come inbound over the ocean. I am extremely happy with progress to date as I continue to focus on operational techniques. The setup is not “clunky” and deploys quickly. I live in a dense neighborhood and will operate from a parking lot with open vistas down by my local beach.

          There are going to be issues and this is my list on ongoing challenges…

          • Cabling is an issue. Sometimes the mount will slew in an unexpected direction. I continue to research this with iOptron.
          • Hamlib. I believe Hamlib is expecting the mount to be connected via serial port and not TCP/IP. Working on this.
          • Cat control between MacDoppler and FLDIGI. I would like to use CW macros. I am working on the config for this.
          • I am continuing to tweak the configuration of cabling, cable routing, phasing, and circular polarization switching.
          • I continue to improve the Python script for telescope mount control.
          • Look at updating the Arrows to the larger Alaskian Arrows.
          • Review other program control including Hamlib together with gPredict. I don’t use Windows portable, but I will confirm functionality via a VM with some of the Windows programs available.
          • Adding 23CM as there are a few satellites which switch modes on a regular basis.
          • Review the need for preamps at the antenna.
          • Building a single antenna solution on the most inexpensive goto mount I can find.
          • Adapt the Meade LX65 mount. Upcoming passes identified by MacDoppler will be used to set the Meade to follow the next object. The Meade mount will operate independently of macDoppler during passes. I will need a wifi serial interface.
          Playback at 2x to see antenna mount tracking satellite. A pic of current phasing. I will get to circular polarization eventually, but today linear polarization is working ok for me.

          Brightness, altitude & azimuth for satellites? - Astronomy

          I have just received a GeoClock program that runs on my PC. It graphically shows the position of the sun and gives figures for Azimuth and Elevation. I'm confused about what Azimuth and Elevation mean in reference to plotting the sun's course across the sky. Does one represent the position from North to South and the other represent the position East to West? This is very basic, but its been so long that I have used this information that I've lost track. Thanks for your help!

          Azimuth represents the cardinal direction in which the object (in this case, the sun) can be found. It varies between 0 and 360 degrees. 0 degrees would be north, 90 east, 180 south, and 270 west.

          Once you know in which direction the object is located, you need to know how high in the sky to look for it. That's where Altitude comes in. Altitude ranges from 0 to 90 degrees, and measures the angle between the horizon, you, and the object. An object with 0 degrees altitude is right on the horizon, while an object at 90 degrees altitude is directly overhead. If you stretch out your arm and make a fist, then your fist covers about 10 degrees on your field of vision, so if the sun is at 40 degrees altitude, it is about 4 outstretched fists above the horizon.

          Occasionally, you will see altitudes less than zero, e.g. "At 9:30 PM, the sun will be at -20 degrees altitude." In this case, the sun would be 20 degrees below the horizon, you would be unable to see it, and it would be night time.

          This page was last updated June 28, 2015.

          About the Author

          Dave Kornreich

          Dave was the founder of Ask an Astronomer. He got his PhD from Cornell in 2001 and is now an assistant professor in the Department of Physics and Physical Science at Humboldt State University in California. There he runs his own version of Ask the Astronomer. He also helps us out with the odd cosmology question.


          Brightness, altitude & azimuth for satellites? - Astronomy

          Basic Patterns and Motions of the Sky

          Imagine the Universe as extending out into space in all directions. When we stand on the surface of the Earth, we can only see at most half of the Universe, the other half being blocked by the body of the Earth. We call the part we can see, the sky . Think of the sky as painted, or projected, onto the inside of a dome--like a planetarium dome.

          Azimuth
          The directions around the horizon are the familiar directions North, East, South, and West (N, E, S, W). We can specify coordinates, in degrees, by assigning N as 0 , and increasing eastward (E = 90 ), through S (180 ), W (270 ) and finally back to N (360 ). We call such coordinates the azimuth coordinate.

          Altitude
          The angle of a star or other object from the horizon is called the altitude coordinate. A star on the horizon has an altitude of 0 degrees. A star straight overhead has the maximum altitude of 90 degrees. Why is this the maximum? Because if a star in the north has an angle of more than 90 degrees, then it has an angle of less than 90 degrees from the south horizon.

          Angular Measure
          We can pinpoint a star or other object using the pair of coordinates, altitude and azimuth, i.e. (30 degrees, 45 degrees) means the star is thirty degrees above the NE horizon. but if we want to be really accurate, we may want to specify the position to better than a degree. We divide degrees into arcminutes (or minutes of arc ), which is 1/60th of a degree, and arcseconds (or seconds of arc ), which is 1/60th of an arcminute, or 1/3600th of a degree. For shorthand , we use the symbols ' and ". Thus, an altitude of 35 d 27' 15" means an angle of 35 degrees, 27 arcminutes, and 15 arcseconds. So remember, 1 degree = 60' = 3600".

          Meridian Line and Zenith
          The point directly overhead is called the zenith . Note that if the Sun is ever at the zenith, then your shadow would be directly under you. This never happens in Newark, but in some places on the Earth it does, which we will discuss later. The imaginary line from the north point on the horizon through the zenith to the south point on the horizon, is called the meridian or local meridian . This is a very important line in the sky, as we will learn shortly.

          When you see the night sky on a dark night away from city lights, you can see at most about 1000 stars. You may pick out patterns in the stars--in general this is a natural function of the human brain, to find patterns. However, these patterns are for the most part random chance groupings of stars, and the stars are not actually related. Two stars may appear close to each other in the sky, but actually be thousands of light years apart in distance.

          Asterisms and Constellations
          Ancient civilizations and cultures noticed apparent groupings of stars and gave them names. Usually the names are associated with myths or legends of human or supernatural events. We call such groupings by two names-- constellation (a group of stars officially recognized by astronomers) and asterism (a group of stars that form a recognizable pattern, but is not officially recognized). A well-known example is the Big Dipper , which is an asterism and is part of the constellation of Ursa Major (the Big Bear).

          Official Astronomical Boundaries
          The constellation names were standardized in 1928, to agree with the names known in Europe at the time, but almost all cultures had their own names and stories.

          Modern usage of constellations now refers not to a set of stars, but to areas of the sky, within official boundaries set by the committee in 1928. In this way, a faint galaxy found in some area of the sky can be said to belong to the constellation within whose boundaries it lies. For example, the Andromeda Galaxy is found in the constellation of Andromeda.

          Milky Way
          When you look at a really dark sky, like you might see in the country far from city lights, you can see a faint path of milky light running across the sky. This is the combined light of the billions of faint stars making up our galaxy, and is called the Milky Way. In addition to the light, you may see dark patches where there appear to be fewer stars--these are dust clouds, which are a common feature of spiral galaxies.

          Sun, Moon, and Planets
          In addition to the far away stars, and the even farther away faint Milky Way, you can also see a variety of nearby objects--members of our solar system. This includes, of course, the Sun itself, as well as the Moon and 5 of the planets, Mercury, Venus, Mars, Jupiter, and Saturn. These 7 objects were called for the latin planetes , meaning wanderers. Did you know that the Sun and Moon were called planets? Nowadays, we would classify the Sun as a star, and the word moon is reserved for members of the natural satellites orbiting planets, but that was not the original meaning. Both the Sun and Moon appear as large objects in the sky, but the other planets appear only as points of light, indistinguishable from stars except by their brightness and their motion (hence wanderers).

          Meteors, Comets and Aurorae
          You may occasionally see comets if you know where and when to look. Some of you may have seen comet Hale-Bopp, in 1996. On any given night you may also see a meteor, also called a shooting star , or falling star . Most are really just a sand-grain-sized pebble of space dust, actually a piece of a comet, hitting the atmosphere. Several times per year there are meteor showers, which occur when the Earth passes through a comet's orbit. Finally, solar storms can cause aurorae, also called northern lights, which you may see as shimmering rays or curtains of light all over the sky. They are rare in New Jersey, but common in Canada and Alaska.

          Coordinate Name Type Conceptual
          Framework
          Reference Point
          celestial coordinates absolute celestial sphere center of the Earth
          altitude and azimuth
          coordinates
          local sky dome our local surface of the Earth
          The celestial coordinates are based on extending the familiar points on Earth up into the sky, i.e. extend the equator to become the Celestial Equator , extend the north pole to become the North Celestial Pole (NCP) , and extend the south pole to become the South Celestial Pole (SCP) . We also extend lines of longitude and latitude, but because the Earth spins we have to pick a particular date and time to do the extension. We pick midnight on the first day of spring as the moment when the celestial and Earth coordinates line up.

          Tilted Coordinates
          One difference in these two coordinate systems is that the celestial coordinates are tilted relative to the local coordinates, by an amount that depends on where we are on Earth . If we are at the Earth's equator, then the celestial equator will go overhead, directly from east through the zenith to the west, the NCP will be on the north horizon, and the SCP will be on the south horizon. If we are at the Earth's north pole, the celestial equator will run all the way around the horizon, the NCP will be at the zenith, and the SCP will be directly under our feet. If we are at some other north latitude, say in Newark, the the NCP will be at some angle from the north horizon, the celestial equator will be on a tilted path from east to west, but not reaching overhead, and the SCP will be below the horizon at the angle exactly opposite the NCP. Note that the altitude of the NCP is exactly equal to your latitude on Earth .

          The Ecliptic, path of Sun and planets
          The Sun and planets (and the Moon) all follow a path in the sky that is tilted from the celestial equator. This path is called the ecliptic (because it is on this path that eclipses occur). There are 12 constellations along the ecliptic, and these make up the zodiac . The Sun appears in each of these constellations in turn, one per month, and their names may be familiar to you as your "sign" -- the constellation that the Sun is supposed to be in during the month of your birth. This "motion" of the Sun is an apparent motion, caused by the orbit of the Earth around the Sun. The planets follow this same path, because the planets all orbit the Sun in more-or-less the same plane . During the orbits of the planets, the Earth "catches up or falls behind" another planet, so that the path of the planet we see may describe a loop. Normally, the Sun and planets all move eastward in the sky with respect to the stars. When a planet appears to move westward, the motion is called retrograde motion.

          Phases of the Moon
          The Moon also follows the ecliptic, because its orbit around the Earth is also near the same plane as the planets. As it orbits the Earth, we see it change phase, from New to Full and back again. You should become familiar with the names of the phases (see Phases of the Moon web page). Here is the image from the text: <Moon Phases>.

          • Rotation (spin leads to 24-hour day) -- about 1000 km/h (600 mph)
          • Revolution (orbit around the Sun leads to 365 day year) -- about 100,000 km/h (60,000 mph!)
          • Sun's motion through the galaxy (relative to other nearby stars) -- about 70,000 km/h (40,000 mph)
          • Sun's orbit around the galaxy (along with other nearby stars) -- about 1 million km/h (600,000 mph!!)
          • Galaxy's motion within Local Group (moving toward Andromeda galaxy) -- about 300,000 km/h (180,000 mph)
          • First day of spring ( vernal equinox ) is around Mar 21.
          • First day of summer ( summer solstice ) is around June 21.
          • First day of fall ( autumnal equinox ) is around Sep 21.
          • First day of winter ( winter solstice ) is around Dec 21.
          • The northern hemisphere summer starts in June, while the southern hemisphere summer is 6 months later, in January!
          • The Sun is up for a longer time in summer (longer days) and a shorter time in winter (longer nights).
          • The Sun is up for 6 months at a time at the Earth's poles, and it is night for 6 months.
          • The Sun rises higher in the sky in the summer, and is lower in the sky in winter.
          The Moon orbits the Earth, and travels with the Earth about the Sun. Sometimes the Moon gets between the Earth and the Sun, causing solar eclipses , and sometimes the Moon goes into the Earth's shadow, causing lunar eclipses . We want you to have a good understanding of how, when, and why eclipses occur, so pay special attention to this part of the course and work hard to visualize it!

          Solar and Lunar Eclipses
          As the Moon orbits the Earth, its orbit is tilted slightly (about 5 degrees) from the plane of the orbits of the planets (the ecliptic plane). It crosses the ecliptic plane twice during its orbit. If this crossing happens at the phase of the New Moon, the Moon will be lined up with the Sun and pass in front of it. This alignment has to be perfect in order for the Moon to completely cover the Sun, which happens only for a small part of the Earth. If it lines up perfectly, it is called a total solar eclipse : then the sky will darken just like nighttime, and the stars will be visible. Total solar eclipses are spectacularly beautiful, as seen in the image below.
          The 1991 total solar eclipse, Steve Albers

          Note: It is often hard for students to see why this doesn't happen every month, and the problem is made worse by drawings such as the one below. We have to use such a drawing so that you can see the geometry clearly, but this top drawing is NOT a scale drawing!

          A more accurate drawing is as shown in the second figure, above. On this correct scale, the Earth is the size of a pinhead, the Moon is the size of a grain of sand, and you can see that getting the shadow of a grain of sand to fall on a pinhead is not easy! So total eclipses are rare for any one place on the Earth. But partial solar eclipses (where the Sun is only partly covered by the Moon) occur about once every 6 months.

          When the Moon goes to the other side of the Earth (the Moon is a FULL Moon at this time), it can pass through the Earth's shadow. This is called a lunar eclipse . This is a case of a pinhead (Earth) shadowing a grain of sand (Moon), which is much easier to do, so lunar eclipses are somewhat more common than solar eclipses. The following drawing can help to understand when solar and lunar eclipses occur, and why. It shows the Earth-Moon system at several places around the 1-year-long orbit of Earth around the Sun. On each lunar orbit, the Moon is drawn at two positions, new-moon and full-moon. The Moon crosses the ecliptic twice each orbit, along the line of nodes . For half of the orbit, the Moon is above the ecliptic, and for the other half the Moon is below the ecliptic. When the line of nodes is aligned with the Sun, that is when eclipses occur--a solar eclipse at the time of new moon, and a lunar eclipse at the time of full moon.

          Here is the image from the text:. <Moon Orbit> .


          Vixen Space Eye 70mm Alt-Azimuth Refractor

          As a confirmed telescope addict, I’m often asked to recommend an inexpensive “starter” telescope for a child or novice on a budget. At some of the public outreach events of the Buffalo Astronomical Association, I’ve groped with the difficulties of pointing the way to something that won’t instantly kill a budding interest in astronomy.
          Many decades ago, my own beginnings in amateur astronomy were almost terminated by a long-focus 32mm refractor on a ball-joint mount that oscillated wildly with the slightest touch. Fortunately, a wonderful Unitron 60 mm saved me and sent me down the path of spending huge chunks of my disposable income on bigger and more capable instruments.

          Today, there are myriad choices in low-cost telescopes, most of them imported from mainland China. However, the vast majority of them feature decent optics, rendered almost useless by cheap plastic parts and pathetically engineered mounts. Many of these 60mm refractors and 75mm to 114mm reflectors COULD serve as a viable introduction to observational astronomy, but finding and tracking objects with them is an exercise in frustration.

          In trying to get some sense of the bottom of acceptability, I purchased a Vixen Space eye 70M alt-azimuth refractor instead of another unnecessary eyepiece. At a street price of about $140, the Vixen is priced above the “bottom-feeder” varieties, and the consistent reports of solid Vixen quality for most of their instruments offered some measure of hope.

          The Space Eye 70 arrived in perfect condition, well packaged in an attractive “gift box” featuring the usual spectacular Keck and Hubble photos that promise a great deal more than the telescope can actually deliver. Form-fitting Styrofoam ensures that components are not subject to shifting and potential damage while the package is in transit.

          Assembly of the scope was simple and straightforward, a decent set of instructions making the task quick and efficient. The instrument is an amalgam of metal and plastic, actually quite attractive with its gloss white aluminum tube with a black plastic lens cell, dew cap, and 1.25” rack & pinion focuser. A mounting point with two protruding screws allows attachment of the 5 x 20mm finder with a plastic bracket and set of fastening knobs. The 1.25” 90 degree mirror star diagonal is fashioned of black plastic and is secured in the drawtube by a setscrew. Two generic 1.25” Plossl eyepieces and a plastic dust cap complete the ensemble.

          The mount for this Vixen is unusual in that it features slow-motion controls for both altitude and azimuth along with locks for tensioning both axes. The mount is metal, finished in a nice looking black crackle. It sits on an adjustable extruded and very light aluminum tripod that has plenty of height adjustment available for seated or standing observation. A small tray at its center has holes to accommodate a number of eyepieces.

          The optical tube attaches to the mount with a captive knob and an additional safety lock.
          Not at all a bad set-up.
          When fully assembled, the Vixen weighs in at a feathery 6.5 lbs., easily movable by a child, but SO light that a gust of wind or a curious family pet could send it tumbling. The narrow angle of the tripod legs puts the center of gravity in a precarious state, so caution is advised.

          The Space eye 70M is a 70mm, f/10 achromat of the classic crown and flint configuration. Two eyepieces are included with the scope: a 20mm Plossl for 35x and a 10mm Plossl yielding 70x – good choices as it turns out, though the 20mm displays a healthy dose of field curvature.
          The objective lens was clean, perfectly collimated and coated, presumably with MgF2, as there were reflections visible when the lens was viewed head-on.
          But are all 70 millimeters of the objective lens in use? Looking through the scope without an eyepiece, I found that the outer perimeter of the objective lens was not visible. A rough estimate indicated that 65 to 66mm of the lens was actually being used, baffles in the main tube and drawtube cutting a bit into the light cone.

          The optical quality, nevertheless, is surprisingly good. Even with the cheap 1.25” mirror star diagonal supplied, the Vixen generated a pretty nice star test, which showed no astigmatism and diffraction-limited correction for spherical aberration. As expected, there is a dose of chromatic aberration, but the false color with an achromat of this aperture and long focal length is not obtrusive at low and medium powers.

          On a cold January evening (about 12 degrees F.) with the telescope cooling for 30 minutes in an unheated garage, the test on a variety of commonly observed objects was on.
          The nearly full moon was very sharp with excellent contrast and almost no false color at 35x. A thin purple rim manifested itself at 70x, but the image remained sharp. These views would undoubtedly be very pleasing to a novice observer, especially with the orb near first quarter.

          Jupiter, high in the southern sky and brilliant, easily displayed its four Galilean satellites at 35x, and when the magnification was doubled, revealed the North and South Equatorial Belts with one tiny northern “barge” and some detail in the southern component. There were hints of dusky polar areas and fainter belts. At 140x, with a 5mm Orion Ultrascopic, the image remained quite sharp, and detail in the belts was better resolved, though the brightness of the Jovian disk became compromised.
          (Unfortunately, the telescope shook so badly at this power that exact focus almost impossible to achieve, and tracking was a frustrating chore.)

          Double stars were also handled well by the Vixen. Albireo was a lovely sight at 35x as its vivid colors were nicely maintained. Sinking low into the northwestern sky, the classic double-double, Epsilon Lyrae, surprised me with resolution at 70x and a satisfying split with the power bumped up to 140x. Resolving this pair is pushing fairly close to Dawes’ limit for a small scope, but the Vixen’s optics were good enough to get the job done.
          Observing Castor at 70x, I found the split to be clean and easy, solid airy discs and a delicate first diffraction ring being just visible. With the power doubled, the view was still relatively sharp, but the stars’ colors took on a yellowish cast instead of the authentic white.
          Rigel turned out to be a tougher challenge. The faint companion faded in and out of view at 70x as the seeing varied and created a swollen primary star.

          I didn’t expect much for deep-sky performance from this small refractor, but it did serve up a pretty decent image of the Orion Nebula, albeit a faint one with the “bat wings” being just visible and any trace of any color lacking. The Trapezium, however, did show four neatly defined points at 35x.
          That same 35 power did a solid job of framing the Pleiades, the stars forming tight pinpoints spread on a dark sky background.

          Overall, the optics of the Space eye 70 do their job well – enough to inspire a real interest in observational astronomy in spite of its limited aperture.

          If only the mechanical features of the telescope matched the quality of the optics!
          While conceptually pretty decent, the mount suffers from the same “shake, rattle and roll” syndrome of almost every low-cost telescope. With both axis locks tightened so the slow-mo knobs engaged, damping time was between 3 and 4 seconds after a sharp rap on the tube. This sounds reasonable, but any attempt to touch the focusing knob created the same effect, making accurate focus difficult to obtain.
          The slow motion controls did nudge the scope along with less vibration, but their feel was non-linear, and (especially in altitude) they had dead spots where they provided no motion whatsoever. The knob for tension in altitude had to be adjusted carefully, and frequently, in order to allow acquisition and eventual tracking of objects.
          As problematic as this seems, it is still better than the frustration generated by cheap “mini-fork” mounts found on the majority of inexpensive refractors.

          The R&P focuser is another sore spot. Though its motion was fairly smooth, it drooped a few millimeters with the unit racked out to normal focusing depth. I removed it, tried to shim it with thin plastic, felt, and a variety of other materials – but without success. In actual use, this turned out to be a minor annoyance, but with its wobble, the focuser won’t be mistaken for a decent Crayford.

          The 5x20 finder, small by any standard, displayed mediocre optical quality, but it did sport a crosshair reticle and a helical focuser for its eyepiece. The problem occurred in trying to align the finder with the main telescope: the three-screw arrangement with a plastic sleeve to anchor the front end of the finder bracket made for a lengthy period of fiddling. I finally gave up for “close enough” in the upper left quadrant.

          If it seems that I’ve been overly critical of the Space eye 70, I may have unwittingly removed the scope from the context of its very reasonable cost. This is obviously an instrument built to a strict price point, and its shortcomings can be forgiven if the prospective buyer can live with a less-than-optimum mount, focuser, and finder.

          Yet, the scope has very good optics and offers a lot of desirable standard features not found in the competition. It could serve as a decent starter scope for a child, but might not satisfy a novice teen or adult who would benefit from more aperture and stability.

          Overall, this little Vixen is surprisingly competent for its price, and it’s a whole lot better than my first little refractor of years ago. So, with reservations in mind, it’s not a bad choice.


          Watch the video: A 4 4 altitude and azimuth (January 2023).