Free Star Maps!

Star Maps or Star Atlases are peculiar things. Imagine making a map of New York City when you can only view it from the Hoboken waterfront. It’d be quite a different map than those top-down street views we’re all used to navigating with. That’s kinda like star charts, which “map” how the stars and other celestial objects look from our particular vantage point, through the portal of the night sky on tiny spaceship earth. Given the scales of the universe, there really isn’t a better vantage point to draw a map, or a better way to draw it (anything that tried to represent actual distances, even at greatly reduced scale, would be unusable and probably larger than the planet).

It’s useful to remember that star maps show us how things look from here, not how they are. Two stars that appear very “close” together in the sky might be (in real terms) much farther apart than two stars on opposite sides of our sky. Our binocular vision fails us at such great distances. Similarly, some brighter stars are farther away than dimmer stars. It all depends on how bright they really are combined with how far away they are. The sky is flat, much like the ancient earth.

In the second half of the 20th century, most amateur astronomers aspired to use Antonin Becvar’s Atlas Coelhi (Atlas of the Heavens). Becvar was a Czech astronomer and the work was compiled at the Skalnate Pleso obseveratory in the Tatra Mountains. I’ve been there, and I can imagine the exciting (and tedious) work making what was then the most detailed sky map ever, all drawn by hand and without the help of either computer datadases or plotting. The opus is also called the Skalnate Pleso atlas. It’s still used today, even though the RA coordinates are a bit out of date. But in it’s day it was expensive.

The update of Skalnate Pleso is Wil Tirion’s Sky Atlas 2000. Like Becvar’s work, Tirion’s atlas is large and not cheap. The pages are unwieldy at the telescope. You almost need a folding table to put them on. The best field version is laminated, but they’re still big and hard to carry, and again, are not free.

Kids, buying things is not punk. At least, buying things when very similar free things are freely available, is not punk. And copywrite is not punk. Do-it-yourself is punk, and so is free. I’d like to highlight several free star maps that can be downloaded from the internet and, in some cases, even redistributed in print or online form. While it might cost a little to print these out on a photocopier, the price will still come in under a commercially-available atlas.

We’ll start with the most basic. Every month since 2000, Kym Thalassoudis has published the Evening Sky Map as a free download from www.skymaps.com

In my opinion, this map is far better than the color ones published by Sky & Telescope and Astronomy. They’re more readable, have better information for a beginner, and, THEY’RE FREE! The prominent feature of the two-page (one front and back) publication is a large circular map of the sky with instructions for use. To the left of that is a calendar of astronomical events that month. The B side has notes, instructions, a very helpful glossary, and a list of celestial objects that you can see with the naked eye, in binoculars, and with the aid of a telescope. For all the information that is packed in, the design is extremely clean. It’s a work of graphic design art.

This is a great tool with which to learn the constellations, find planets and the brightest of Deep Sky Objects. The Evening Sky Map’s usefulness for outreach cannot be overstated; for a pittance a pile of them could be printed and distributed at star parties and other public viewing activities.

When you know the constellations and have binoculars and/or a telescope, Andrew Johnson’s Mag 7 Star Atlas Project is the next free download you should print out. It charts the apparent sky in 20 maps, showing stars down to magnitude 7 (hence the name!) and 550 Deep Sky Objects, including the brightest from the Messier and NGC lists.

Andrew Johnson

There’s a version in black and white, and a pretty color one that shows the Milky Way. It’s licensed under Creative Commons, so it can be widely distributed for non-commerical purposes. This would be a great step up from the Evening Sky Map as you learn more about the night sky, and will guide you to many wonders that can be easily seen with binoculars and small telescopes, including those listed on the Evening Sky Map’s flip-side.  Johnson also includes many double stars which are really fun objects to explore. You can download it at:

http://www.cloudynights.com/item.php?item_id=1052 or from the internet archive: http://www.archive.org/details/Mag_7_Star_Atlas

These two tools can keep a beginning astronomer busy for many nights!

Up the scale in complexity is Toshimi Taki’s 8.5 Magnitude Star Atlas. This one is different than Johnson’s Mag 7 Star Atlas Project in format. It’s A4 sized maps (you can shrink them a tad to fit US letter-sized paper) show you much narrower swatches of the sky, and are much roomier. If course, there are more of them and so that makes navigating between the 146 separate charts more of a chore. But for star-hopping to fainter objects, Taki’s Mag 8.5 would be a very valuable tool. It charts more stars than Tirion’s Sky Atlas 2000 and almost 3000 Deep Sky Objects.

Taki’s atlas can be downloaded from http://www.asahi-net.or.jp/~zs3t-tk/atlas_85/atlas_85.htm

A page from Taki

Lastly, there’s José Ramón Torres and Casey Skelton’s Triatlas Project. This is an expansive and impressive three-part work, as the project title suggests. There are three sets  of charts. The A set consists of 25 charts reaching to Magnitude 9. The B set has 107 charts reaching to magnitude 11, and the C set (get ready!) has 571 charts, with stars down to Magnitude 12.6. Basically it charts pretty much every star you can see with a medium-sized amateur telescope of 10 inches.  The author believe in offering choices, so they have all charts available in pdfs formatted for US letter sized printing in addition to A4, and they have an “intermediate” B/C set of charts that lies between the two large sets.

I printed out the same map from each atlas, A2/B12/C93, showing most of the constellation Cygnus. Interestingly, the higher maps reference the lower ones the C93 chart, for example, has A2/B12 written on it so you can hop down to wider and less deep views, but not the other way around. The Triatlas is not for the faint of heart. All of the charts are packed with stars and a loupe wouldn’t be a bad idea. And, although the stars the C set charts are visible with a 10-inch scope,  I wouldn’t recommend it for use with that aperture unless you have really dark skies. Still, the Triatlas represents quite an achievement and would be useful for owners of large dobsonians and access to very dark skies.  The Triatlas lives online at: http://www.uv.es/jrtorres/triatlas.html

A page from the C-section of the Triatlas. Be afraid, be very afraid.

Some people use planetarium programs on computers while observing. There’s lots of good programs out there, as well, and some of them are also free, non-copywrited and therefore totally punk. But they’re out of the scope of this article. Many people (myself included) stare at a computer all day, and find that using a laptop outside, while observing, somehow feels wrong. Not to mention that the planetarium programs sometimes show you a nicer sky than what nature, or human development, allows you to see above your head. There’s something utilitarian and satisfying about paper maps, and frankly it’s much easier to notate them than with planetarium programs. And with printouts costing just a few cents a page, there’s no reason you can’t fill up your atlas with personal notations about what you saw, and when. Except with the Triatlas…there’s no room to do that!

NOTE: One reader submitted that technically these atlases are not open-source, since you can’t really modify them very easily. This is true, so I have removed that from the title and references to open-source in the text. The program that was used to make Andrew Johnson’s Mag 7 atlas is an open source software called PP3. http://pp3.sourceforge.net/

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One thought on “Free Star Maps!

  1. I agree with you that the sky atlas made by J. R. Torres is “impressive”. In my opinion it’s the best night sky atlas that there is in any form and it’s simply amazing that its author is offering it for free to the world.

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