XEphem 3.5.2

“OK, <yawn> that’s great. Think I’ll just be running along now.”

Hold on just a darned minute! You want pretty pictures? Here they come. Click on the view menu and choose the Moon. Up comes the beautiful rendering of the Earth’s sister. You can do the same with other planets. Mars is particularly impressive from a graphics standpoint, while the Jupiter and Saturn choices depict the great planets’ retinues of moons (and Jupiter shows off its Great Red Spot in the right location).

But the real reason most people obtain an astronomy program is for a depiction of the sky. To get that, just click “sky view” under the “view” menu. Up comes a depiction, a lovely depiction of the entire “skyglobe” . What you with this skyglobe is up to you. With the proper catalogs downloaded and installed (this is easy to do, and like most things in this program, is handled from the main menu), you can easily obtain a very detailed view. This shows the great Virgo galaxy M87 and its little attendants. To create this I loaded up the Tycho 2 star catalog and the CGCG galaxy catalog that I’d downloaded off the net. Copies of these resources converted to XEphem format were easy to find on the web, but making other downloadable catalogs into XEphem files is relatively easy. As you can see, the final result is very competitive with some very well-regarded commercial Windows programs. Better than quite a few that I’ve wasted my hard-earned bucks on, I’d say!

But you don’t have to stop. Need more stars? XEphem will read the Hubble Guide Star Catalog CDs sold by the Astronomical Society of the Pacific. Can’t afford—or don’t want to afford—these? No problem. As long as you can get your Linux computer on the Internet (Red Hat comes with a copy of Netscape Navigator for the included Gnome X-Windows desktop) you can download all the stars you need for free. XEphem will go and get GSC stars as needed, a process that’s pretty seamless if you have an always-on broadband Internet connection.

You can, naturally, manipulate your onscreen view as you wish by zooming and moving around the sky, just as you can with any Windows planetarium. This is another place, admittedly, where XEphem goes its own way. Most of your movement will be done with scroll bars. The left slider controlls zoom, and the right one Right Ascension or altitude (depending on if you’ve selected RA/DEC or ALT/AZ on the toolbar at the top of the screen). The bottom scroll controls the remaining axis—declination or azimuth as required. Or you can right-click on objects or locations on the screen and choose “center” from the resulting menu of choices to move around. But the sliders work so well that I seldom resort to this. On a modern PC with a modern video card, Linux and XEphem run so smoothly, that the changing display as you scroll around is a joy to watch: fast, smooth, and precise.

The alt/az/RA/dec sliders are nice. But I did not really like the zoom slider, I must admit. I’m so used to the method other astro programs use, drawing a box with the mouse and clicking to zoom, that the slider seemed awkward and different. But XEphem provides an alternative (“alternative” is a word you use a lot in association with XEphem--almost as much as “free”). You can click a button on the right toolbar to enable box-dragging. Once you’ve drawn a box enclosing the area of the sky you’re interested in, you click the “+” zoom button on the right-hand toolbar to zoom. Not quite the same as dragging and clicking in the box as we’re used to with other planetariums, but still warmly familiar.

XEphem is that fabled Horse of a Different Color in quite a few ways, but Mr. Downey was wise enough to stay close enough to the format we’re used to to make the program very easy to learn. Most of the programs other most-used functions work just as you’d expect ‘em to. In fact, you may even forget you’re using Linux and XEphem once you start concentrating on printing star charts for your next deep sky expedition (XEphem offers excellent printing support). I was taken aback for a moment when I looked at the bottom of the screen, at the taskbar, and didn’t see the familiar Windows Start button! Instead there was the Gnome desktop’s little footprint (don’t ask). “Oh, yeah, this is XEphem!”

Is there anything I don’t like about XEphem 3.5.2? A few things. There is that zoom process. I much prefer the “standard” draw-box-and-click-in-box to zoom rather than XEphem’s draw-box-move-mouse-to-right-side-of-screen-find-button-click-button to zoom. On the other hand, XEphem’s “unzoom” button is very easy to access and use, unlike some Win programs, which require you to open a menu to unzoom. I also occasionally ran into problems when zooming in to small areas. Sometimes the field stars I should have been seeing at increased “magnifications” weren’t drawn very quickly, with 5 or 10 seconds elapsing before a redraw. Sometimes, they didn’t get drawn at all. This was very occasional, though, and I could always fix this by opening the Field Stars Dialog and hitting “apply”. I generally liked the idea of having a separate main menu apart from the Sky View window. This keeps the menus on the sky window uncluttered. But there were a few instances when I wished that some menu choices were in both places or just on the sky menu. But these times were rare. Once you get used to it, XEphem is very ergonomically sound.

How do I rate XEphem against that other well-known freeware astronomy giant, Cartes du Ciel? Well, there’s no doubt in my mind that Cartes is a more mature program. But XEphem is close, and in some ways maybe even superior, if not quite as fancy looking or feature-laden. XEphem is certainly in the lead when it comes to non-Windows computing. The new Macintoshes run an operating system (OSX) that is Unix related/based, and there’s already a Mac version of XEphem for these machines. Each program has its strengths, and I rate both of these programs as “up there” with just about any commercial astronomy offerings. XEphem, like CdC, possesses some fanatically loyal users, and, also like CdC, the author has set-up a Yahoo mailing list for the program’s fans. Elwood Downey is OFTEN found there “in person”, answering questions from users, taking suggestions, and moderating an enthusiastic group of Linux-loving Astro-software hounds!

I love XEphem, and if you can make peace with the Penguin (Linux), you will too! If I can help you get XEphem up and running, please don’t hesitate to ask for help! If old Rod (who’s still locked in the TRS-80 Model 1 computer days) can get this fine, DEEP program up and running, so can you!

Added:  Friday, August 01, 2003
Reviewer:  Rod Mollise
Score:
Related Link:  Clear Sky Institute
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Language: eng
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