Sunday, April 24, 2011


Sky Charting

Astronomy software is strange and confusing. It’s way different from other astro gear where “more expensive” usually equals “more better.” Price doesn’t always have much to do with how well an astro-program works or looks, as is amply demonstrated by Cartes du Ciel (CdC) and Stellarium. They work good. They look good. They are free. I intend to give you the straight poop on Stellarium real soon, but for now let’s focus on everybody’s fave freeware, Cartes du Ciel, “Sky Charts.”

Me and Cartes go a long ways back, back to the late 1990s. At the time, I didn’t have Skytools. I was experimenting with an early “planning” type program, Deepsky, but mostly I was using planetariums, programs whose whole raison d’être is to display a simulation of the night sky on your PC screen. My favorite was Emil Bonanno’s famous (still) Megastar.

Megastar was a fantastic program, throwing up the deepest charts I had ever seen, but it was weak on the sky simulation part of the planetarium equation. It was more a computerized atlas than it was a simulacrum of the sky. There wasn’t much in the way of animation, planetary simulations, or even horizons. For those reasons, I was still clinging to that hoary DOS (what came before Windows, younguns) application, SkyGlobe.

I’m not sure who first told me about Cartes du Ciel. Probably it was my late friend Jeff Medkeff. He was the first astronomy software guru I’d run into, and I figured if he thought the program was worth a look, it was worth a look. Wouldn’t cost nothing to try it, anyhow. CdC was not commercial software or even shareware, it was free, given away by its Swiss author, Patrick Chevalley.

The version of Cartes that went on my Compaq Pentium must have been an early one, likely prior to version 2.0. It ran OK on my Windows 98 box, but, truthfully, it wasn’t quite there. It was a little slow at times and lacked a little in usefulness as well as usability. The user interface left me slightly baffled, too. “Missed it by that much.”

I liked what I’d seen, though, and hoped the author would continue to develop his program. Since the producer of Skyglobe had dropped out of the game, there really weren’t any freeware astronomy standouts (actually, Klass-M Software’s Skyglobe was shareware). Freeware programs come and go, but I had the feeling that if Patrick stuck with it, CdC might become a big success—in a small amateur astronomy way.

I kept my eye on Cartes, and my watchfulness was rewarded the following year, 1999, when Patrick released the first full-up Cartes, Version 2.4, which is the grandpappy of what is probably the most widely used non-commercial amateur astronomy program of all time, Cartes du Ciel v2.76.

As soon as I downloaded and booted 2.4, I could see the puzzle pieces were falling into place. And by the time the first of the 2.7 versions appeared two years later, I knew we were there. Not only had Patrick worked the bugs out of his program, he’d radically improved the interface and made plenty of catalog data available.

Back then, everybody was still obsessed with how many stars and deep sky objects a program contained. Maybe because that was something quantifiable, like the aperture of a telescope, and maybe because we were just on the cusp of the amateur astronomy data explosion where we suddenly went from “ALL THE MESSIERS, OVER 200 NGC OBJECTS, AND THE ENTIRE YALE BRIGHT STAR CATALOG!” to millions of stars and DSOs.

CdC had the chops: the famous SAC (Saguaro Astronomy Club) deep sky catalog was included in the basic package, and you could easily download and install not just the NGC, but catalogs that added millions more objects, like the enormous PGC catalog of galaxies. Stars? You could get the Tycho 2 catalog from Patrick’s site. Not enough? If you had a source for the Hubble Guide Star Catalog (GSC), the program would happily use that, too. There’s long been a cooperative symbiosis between CdC and Steve Tuma’s Deepsky. Not only could Deepsky use Cartes as its charting engine, Cartes du Ciel could use the Hubble GSC files that shipped with Deepsky.

But it wasn’t just catalogs. CdC had a lot more going for it than that. With 2.76, the software added realistic planets, nebula isophotes, and more. Cartes sported some features not found elsewhere, as well. Like the ability to download Digitized Sky Survey images and overlay them on charts (hell, you could even do that with your own astrophotos).

One thing that seemed irksome back in the astro-ware dark ages was that Cartes didn’t have native telescope control. If you wanted to send one of the increasingly popular robo-scopes on go-tos with the program, you had to use a “helper” application, ASCOM. It was odd to have to use an add-on program at first, but it wasn’t long before most of us thanked our lucky stars Cartes went the ASCOM route. ASCOM meant the program would always be up-to-date scope-wise, able to control nearly any telescope on the market. We’d never have to play the waiting game while the author wrote his own built-in drivers to work with the latest Meade-o-tron.

And so we lived happily ever after, huh? For a while, muchachos, for a little while. Things were moving fast in the astro-ware game, and by the time the first decade of the new century was well-underway, it was clear our beloved Cartes du Ciel 2.76 was ripe for replacement. It still worked well. B-u-t. The display was very legible, but was looking old—it shouted “1990s.” The program’s user interface could stand some fine-tuning, too. Performance might be better as well. The whole thing was written in an obsolete programming language and was a little slow compared to more modern software. It would also have been nice to be able to run the program on Macintosh and Linux machines—CdC 2.76 was resolutely Windows only.

Patrick realized all these things, probably more than any of us, and began work on the successor to 2.76, v3.0, in 2002. It being a part-time labor of love, starting Cartes all over again from scratch took a while. It was not till five years later that we had a beta that was nearly ready for prime-time, and it was three more years after that before the official release of Cartes du Ciel 3.0 hit the streets.

The wait was worth it. This was still identifiably Cartes, but it was a better Cartes. The user interface, including the program’s confusing configuration menus, was reworked and improved. The display looked a lot more modern and pretty. The speed of everything was noticeably better. Best of all, the features we loved most in 2.76 were still there, if slightly changed and rearranged. And now the Apple and Linux fans among us could join in the fun, too.

So Cartes 3.0 is a winner? I answer an unreserved “yes” to that. It is a mature piece of software, though, over a decade old, and it does a lot. That means it can be a steep hill for an astronomy software novice to climb. The first hurdle is getting the program installed and configured, which has scared many an astro-ware tyro badly enough that they’ve given up on the whole thing, which is a shame. Tell you what: why don’t we download and install Cartes and give it a whirl together?

Download and Install

Before you can learn Cartes, you gotta get it, right? In the dial-up days, Mr. Chevalley made CD ROMs available for a nominal fee, but in the age of broadband you just download the program from the CdC 3 site. The basic package, which includes everything you need to get started, including the Bright Star Catalog and the SAC deep sky objects, will run you a mere 22 megabytes. If you are still in dial-up hell, do what I did way back when and get a buddy with a fast connection to download the program (and additional catalogs) and burn ‘em on a CD for you.

You will need several other files in addition to the basic package, but let’s get the main program installed before we worry about that. Go to the 3.0 site, choose the appropriate file for your operating system (most of you will want either the Windows 32 or 64 bit version, depending on your flavor of Windows). After you click on the file, you can save it to a directory on your hard drive, but in the interests of saving time and minimizing confusion, let’s hit “run” on the dialog box Windows throws up, which will download the file and execute the install program automatically.

After a brief or not so brief spell of downloading, the installation program for Cartes will begin. Just respond to the prompts as you would when installing any program, accepting the default values. Your hard drive will grind away for a little while, and, when the program ends, you will find a cute little CdC icon now resides on the desktop. Problems/caveats? Not that I’ve experienced. The program has installed and run normally for me under both Windows Vista and Windows 7.

The Apple Macintosh installation process is derned near as simple. Download the installation file, click to mount it to a “virtual disk,” click open the resulting folder, click “skychart.pkg,” and the installation program will begin. Please note that the program will not run on older Macs with Power PC processors.

How do you load the Linux version? Don’t ask me. I had Red Hat Linux on one of our machines here for a while, but using a Linux/Unix computer at home felt too much like work and I deleted the dadgum partition. There are Linux installation instructions available on the CdC 3.0 website (“Documentation”) which will likely make perfect sense if you are on friendly terms with the Penguin.


Installing CdC, getting it up and running, is barely half the battle. You have to tell the program the usual things astro-programs need to know: location, date, and time. Being a rather deep and capable program, there are some other data entries you need to make too. Let’s get started. Click the CdC icon and fire her up.

The program itself will ask you which language you want to use. I chose “English,” and proceeded to the Setup menu on the Windows menubar. Click that open and you will find a bunch of choices. You could choose just one selection, “All configuration options,” but I find that menu is one of the few things in Cartes that is a little slow and clunky. Instead, I choose individual configuration options beginning with “Observatory,” which means “latitude and longitude.”

There, you can select your State (or province, etc.) and then your city from a variety of choices. Select your time zone with the pull down below and you are done. Or, if you want to use your exact location, the value from a GPS or from Google Earth, you can manually enter your site’s latitude and longitude. Give the location a unique name in the blank under “observatory database” and you are done. Well, almost: don’t forget to click the “Update” button to save your new site. You can also input your altitude, though I have never found doing so has made pea-turkey difference. How about that cool map? It’s cool, yeah; you can move a cursor around to establish your location…but I’ve never found it precise enough to be much use.

Location and time zone established, tell Cartes how to handle time. This is an easy one. Click “Date/time” on the setup menu to open the time window. There, all you need to do right now is click the check-boxes labeled “Use system time” and “Auto refresh every” (if the number in the box next to autorefresh doesn’t have “60” in it, put 60 in there).

Next up is “Chart coordinates,” but you can skip that for now. Same with “Catalog” until you install some add-on catalogs (see below). “Solar System”? Same-same. Light on “Display” and open that. Leave most of the Display menu's tabs alone for the moment. They allow you to fine tune the way things look on screen. The only one you probably want to set up from the get-go is your finder circles. These settings will determine the size of finder/eyepiece circles displayed on the screen. You’ll already have some set and checked; using these defaults will place a Telrad reticle on your display at your command.

If’n you ain’t got no Telrad? Or want an eyepiece field circle? Go to the first blank row, enter the (true) field size for whatever you want to use, and insert a text description for it: “Unk’s 50mm finder” is what I got there. If you know this is the field circle you will want to use all the time, unclick the three Telrad circles, click your new one(s), and click “OK” on the winder.

What else? Nothing else, boys and girls. Not in the beginning. You’ve probably already glommed onto the idea that CdC is MUCHO configurable, and you will no doubt soon come back, especially to “Display,” and do a lot of tweaking of things like object colors, text sizes, deep sky symbols, and a whole lot more, but for now you are good to go. Who said Cartes was hard to set up? Not me, muchachos.

Actually, you aren't quite done. If you, like me, want to install some additional star and object catalogs from the get-go, there’s a little more work to do. Once you have downloaded and installed the extra catalogs you want (see "Additional Catalogs" below), go back to the Setup menu, click “Catalog” and choose the tab of interest, “CdC stars” to begin with. Initially, only “Bright Star Catalog” will be checked. As you download and install additional catalogs, you will come here to turn them on. In addition to checking the box on the left to turn each catalog on, you will have to specify the directory path to the catalog you’ve installed. If the catalog in question was downloaded and installed from the CdC page, the directory will usually be filled in for you. If not, or if you want to enable a user supplied catalog like the Deepsky Guide Star Catalog, just click the little folder on the right and you will be able to pick the correct directory.

“CdC Deep Sky” is the next most often accessed tab. It works just the same as the star catalog menu. Click the check-box to enable the catalog and specify the directory if required (if you turn on a catalog and the directory info turns red, the path is wrong). Note some catalogs may “conflict.” If you’ve installed the NGC and want to use it, you will, for example, probably want to unclick the SAC catalog. Otherwise two object symbols and numbers will be superimposed. CdC will let you do it, but will throw up a warning box. You will be warned about conflicts with other catalog types as well.

Once you are done with the Setup menus, you need to turn on the features you want/need to turn on. You do that with the second of the two horizontal icon bars at the top of the screen. Starting at left, click the button with the stars on it to turn on stars (should be on by default). Next to it is “show deep sky objects,” which you may want to turn on (see below). The icon button to the right turns on “Lines,” by which it means nebula outlines. Next over is “Pictures,” which you click to display the program’s astro images if you have installed ‘em. The button labeled “DSS” allows you to download Palomar Observatory Sky Survey images and overlay them on charts. The next two you can skip for now.

Do turn on “Show planets.” Skip another couple and enable “Show Milky Way” if you want to see the outline of the Milky Way. The next couple of buttons allow you to enable either the equatorial grid lines or alt-azimuth grid lines. Actually, you can have both on, but you probably won’t want to. You’ll definitely want “Show constellation lines,” and you may want the next one, too, “Show constellation limits” (boundaries). The button to the right of that is “Show galactic equator,” which I rarely need and which you will rarely need. “Show ecliptic”? Maybe you do, maybe you don’t; you decide. The oddly titled “Show mark” button turns on and off the finder or eyepiece circles you set up and checked on the setup screen. “Show labels,” should usually be on. Skip the next couple, and ensure “Sky background colour” is off unless you want a bright blue background during your artificial sky’s day. And that is it for now.

Additional Catalogs

Now that you’ve got the program resident on your hard drive and have completed basic configuration, you will want to go back to the CdC download page and download the files you need to make it useful. The place to start is with more stars. The add-on Stars catalog, which includes the Tycho II stars, will give you suns down to magnitude 12, which is all some of you may ever need. Click this file (55 megabytes), and “run” it like you did the basic package. It has an installation program that will, if you leave the defaults like they are, put the files in their proper places.

Gotta have more stars? If you don’t have the Hubble Guide Star Catalog available in the form of the Deepsky DVD and can’t get it from another source, you can still go past 12th magnitude when you need to. There is an alternative, a good one; especially if you are a “power user.”

The UCAC3 Catalog of stars down to the 16th magnitude is available on the CdC download page. This humongous catalog goes slightly deeper than the Hubble GSC and its data is, in general, better and cleaner. The penalty? At least several hundred megabytes to download. Please note that stars brighter than magnitude 10 are not included, so you will need to have already installed and configured the basic Stars catalog. Me? It’s nice to know this big star catalog is there when I need it. One thing’s sure: we have come one hell of a long way astronomy data-wise in just a few years. Seems like just yesterday the GSC was mind-blowing—all those millions of stars—and it is already passé.

Stars taken care of, it’s time to load up on deep sky objects. The SAC catalog included in the basic package has plenty, but I can’t get along with just that. If you can’t either and don’t mind downloading 30+ more megabytes, you can get lotsa DSOs. The add-on DSO catalog has a passel, including the whole NGC and even the PGC. All told, over two million DSOs (most of them PGC galaxies, natch). As before, click on the file to begin the download, hit “run” on the dialog that appears, and accept the defaults the install program offers.

Do you like pictures? I do. They can be a huge help identifying the dimmest of the dim. Cartes du Ciel can download deep sky object images from the Digitized Sky Survey, but it’s handy to have onboard pix for those times you ain’t got no Internet. The Pictures catalog contains images for nearly 10,000 objects, which will be placed on your charts in lieu of symbols when you enable them by clicking the “show pictures” button on the lower icon bar. This is about 30 megabytes of data, but it is well worth your time and drive space.

Getting the pictures going is slightly trickier than enabling catalogs, but not tough. When you’ve installed them, you must first go to the setup menu, click on “pictures,” and select the “objects” tab. When you are there, click the “scan directory” button (the default directory above that should be correct). When it’s done, close the setup window, click the “Show pictures” button, and, counter-intuitively, unclick (turn off) the “show deep sky objects” button two buttons to its left. If you do not do that, the pictures will be hidden by DSO symbols if you have “fill” turned on in the “deep sky colour tab” in the display menu. If you’d like to see both pictures and symbols/outlines of DSOs, go to the display/deep sky colour window and uncheck “fill” after each object type.


Almost done downloading and installing. There’s one more component you’ll need, but only if you intend to send your telescope on go-tos with CdC. That is ASCOM, the famous telescope driver program. ASCOM provides an interface between your scope’s computer and Cartes. I should probably do a whole blog entry on ASCOM someday, but for now we’ll stick to the short and sweet. Go to the ASCOM site and download and install the Version 5 “platform” just as you did the Cartes files. Once you have Version 5 installed, you must run the “platform updater” (there is a link to it on the ASCOM website front page), which will bring you up to the current supported version, 5.5. You’ll need drivers for your specific telescope(s), too. Go to the driver page and download and install the driver(s) appropriate for you.

If this sounds like it’s a lot of (potentially scary) work, it’s not; just do what you did with CdC: click the files to download them, click “run” and allow their install programs to execute if your version of Windows asks for permission, accepting defaults. Remember, you only need ASCOM if you want to interface Cartes to a go-to scope, and if that is what you want to do you must have ASCOM—Cartes du Ciel does not include any telescope drivers.

Using It

When you’ve finally got the dadgum thing set up, it’s time to do something useful with it. As with any other astro-ware, exactly what you will do with Cartes depends on exactly what you are observing and how. This is designed just to get you off ground zero, to give you the very basic basics of CdC use. When you have these down, you’ll no doubt quickly learn and start using tricks and techniques of your own.

Panning and zooming is something we do every time we use a planetarium type program, and Cartes works the same as most programs in this regard. Want to look at the southern horizon? What most folks do is click the N/S/E/W buttons on the rightmost vertical toolbar. Click “south” and you are looking south. Don’t see enough of the sky? Click one of the field of view buttons above the direction buttons, “90,” maybe. Don’t like the button clicking? Your mouse scroll wheel will zoom out and in for you too.

What’s that funky looking round button between the direction and field buttons on the right toolbar? Clicking that will give you an all-sky planisphere type display. To return to the normal display, click the 90 degree field button and the direction button of your choice.

Don’t like clicking buttons to pan around? The OTHER way to move around the Cartes du Ciel sky seems to be unknown to some users: hold down the shift button and drag the sky around with the mouse to get to just the spot you want. Works crazy-good and is smoother in operation than similar features are on some mucho-expensive software.

How do you find good stuff? A big part of any planetarium is object locating, and Cartes du Ciel provides two ways of doing that. Easiest way? Cartes’ quick search button on the top icon bar, the little blank field. Type the object of your choice, “M1” for example, in the blank and mash the return key. M1 will be placed at the center of the screen with a circle around it and a label next to it.

Then there is Way Two, a more sophisticated search engine. To access it, click the little binocular icon on the top row. Select the type of object you want to find, enter its ID either manually or using the buttons at the bottom and away you go. The program is fairly picky about object IDs, but no worse than most and better than some. Either “NGC253” or “NGC 253” will work.

Where the going gets a little tough is in searching for comets. The thing is, before you can find a comet, you gotta have comets. To get comets you have to download the current MPC (Minor Planet Center) comet file. Thankfully for the more computer illiterate—like Unk—CdC makes this pretty painless. Go back to the setup menu, choose “Solar System,” hit the “Comet” tab and then the “Load MPC File” tab. Click the download button, and when the file has downloaded, go back to the search window, type the name or indentifier of your comet in the blank field at the bottom left, hit “Find,” and you should have the hairy star of your choice on screen.

Once you’ve found the object of your desire, you’ll want a good look at it. To zoom in tighter than the field size buttons on the right icon bar, you can use your mouse wheel. Or you can click the “+” and "-" magnifying glass icons on the top icon bar. Or you can draw a box around the area/object and click within that box to execute a zoom if that's what floats your boat.

You’ll also likely want to know a little about your object. Left click on the subject so that its label is highlighted, and a brief description will appear at the bottom of the screen. Need more? Right click and choose “About NGC umptysquat” from the right-click menu that appears.

One of the things about Cartes that has always tickled me is its ability to download POSS plates and overlay them on its charts. To do this, pick an object and zoom in good and tight. The max field size is 2-degrees square. Click the DSS button and a window will appear. Click the “Download” button and the image will be downloaded and automatically overlaid on the chart. When you are done with it, click the little “camera” icon next to the “DSS” icon and uncheck “Show picture.” Note: you will probably want to uncheck the autorefresh button in the time setup menu when playing with pictures or you’ll have to continually re-center the target.

What’s a planetarium program without a little animation? Cartes is not obsessed with these features, but it has tools to allow you to advance the sky easily. On the top icon bar you’ll find forward, back, and stop buttons as well as a pull-down. To move the sky, pull down the pull down menu and select a time increment, maybe “1 hour.” To move the sky forward 1 hour, click the right button. To move it back, click the left button. To return to current system time hit the square “stop” button. Alas, Cartes doesn’t have a mode to automatically advance the sky in increments, though it does have an object animation mode good for building comet and planet paths across the sky.

Running into problems with Cartes du Ciel? There are a couple of ways to get help. There’s the program’s help engine, which is usually good enough to get me out of trouble, though Cartes’ English is a little creaky. Or you can visit the Cartes Yahoogroup, “skychart-discussion,” where you will usually be enlightened by Pat Chevalley himself. Or you can ask your questions on this here blog. I only had time to cover the high points this morning, but I’ve used the program long enough that I should be able to answer most of your enquiries and would be glad to do so.

Last words? You’ll pry Cartes du Ciel, Sky Charts, out of my hands about as easily as you’ll get my Alizée videos from me, and that won’t be easy, muchachos, that won’t be easy. Sky Charts is a classic of astronomy software, and thanks to the selfless and tireless efforts of its author it’s still as up-to-date and as wonderful as ever.

Next Time: Sweet Charity.

Great blog as always. The Alizee link was a great plus.
Thanks Rod. I've just downloaded and installed both programs.
Thanks Rod. I have just downloaded and installed both programs.
I've been trying to figure out how to use the mouse to move around in Cartes du Ciel for weeks. Thanks for the info on using the shift key!
Rod, any suggestions on how to configure CdC for use with the NGC-MAX digital setting circles? Supposedly they can talk to each other but I can't figure out how to set it up.
Is there an ASCOM driver for 'em? If so, it should be as simple as getting the right serial cable and configuring ASCOM, right?
Rod - how can I leave a message. Nothing works. I want someone to tell me how to rid my screen of those pesky CCD frames. I've un-checked them in the setup/display and I've set their valuse to zero, but they keep showing near Aquila. How can I get rid of them?
Tis simplicity itself. Right click on the screen, click "finder circles" in the menu that appears, and click "remove all." You owe me a beer, pard. LOL
Wow that was such a brilliant tutorial on using CDC thank you very much for taking the time and effort to write it up I have just started using it along with the ascom drivers and eqmod and this made my life a whole lot better.

Many thanks Mark.
Nice Blog Post !
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