Earth from space in xephem

Xephem is a Unix/Mac OS X based sky chart and ephemeris program. The program costs $80 for a precompiled version on CD-Rs or by download along with a huge set of catalogues and the Lunar Orbiter images. An identical version is available for download only at $60. This is a 1 Gb download spread over three gzip files. I have downloaded just Cd 1 to get the basics running on my iBook, the Lunar Orbiter photos and large field star catalogues will wait until the CDs arrive.

You can download the source for free and build your own version of the application and then download the catalogues from various astronomicl servers for nowt. Youngsters with access to a broadband connection but limited cash could build their own version and learn about compiling code. You can compile a Windows version under the Cygwin environment but I can think of better things to do on a wet Sunday. The excellent free Cartes Du Ciel might be a better bet for Windows.

Xephem runs under X11 on Mac OS X, and the interface needs some working out – it is nothing like the Mac OS native applications. I’m hacking my way into it – mainly because the program produces excellent PostScript star charts and I can use Preview to pop those into Word (at screen resolution) or incorporate them into TeX documents. The PS files are produced by ‘printing to a file’ from xephem’s print menu and the single page files load directly into my ancient copy of Adobe illustrator. The page size appears to be fixed at either Letter or A4. I’m sure there will be a way of getting A3 charts.

In Mac OS X Preview I can also Copy a part of the PS file and Paste as New and then save the region as a PDF file. A challengecan you recognise this field (PDF, 60Kb)?

The package can fetch data from Web based astronomical databases – including a light curve lookup feature from the AAVSO Web site.

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