Don Shedrick

Feb, 2000

DAS Focus - Feb, 2000

COMPUTERS IN ASTRONOMY by Don Shedrick

In my last article, I wrote about a freeware planetarium program called Home Planet. This month, I will present and compare several other freeware and shareware planetarium and sky charting programs for Windows available on the the Internet.

SkyGlobe is a shareware program widely available on the Internet, available as both a DOS based and Windows based version. It is the planetarium program which will give you the most accurate feeling of sitting under the night sky or in a true planetarium. SkyGlobe, especially in the DOS version, is very simple and easy to use, with almost no inputs or adjustments needed. It is excellent for giving the user a real understanding of how the stars and planets track across the sky, as you can set the sky in motion by tapping the "A" on the keyboard. Explore how all the keyboard letter and function keys, and ctrl B and alt B, change the display. SkyGlobe, however, does not have the vast array of features that Home Planet or Sky Charts have. It is available on many sites on the Internet as the DOS version, but is very hard to find as the Windows version. This web site from a Brazilian astronomy site has both:

http://www.geocities.com/CapeCanaveral/Launchpad/8602/astro/programas.html

PlanetWatch is an entertaining and educational shareware program featuring an atlas of the solar system with a very nice sky chart of the region +/- 30 degrees, or the region of the sky containing the ecliptic. In this region of the sky, the motion of the sun, moon, and planets can be observed by setting the map in motion. The phases of the moon even change as it passes along the ecliptic. With PlanetWatch you can also see each planet's motions in an Orrery style display, photographs of the planets, and learn about planetary atmospheres, geology, and internal structure. For $20, a pro version is available with a few added features and more photos. For more info and download links, visit the web site of the author of this software at:

http://ourworld.compuserve.com/homepages/galen_raben/

Sky Charts is a very powerful sky charting freeware program. This program enables you to draw sky charts with a vast array of options, including the choice of data in 15 catalogs of stars and nebulae, and the position of planets, asteroids and comets. The large number of options allow you to choose which catalogs to use, the color and the dimension of stars and nebulae, the representation of planets, the display of labels and coordinate grids, the superposition of pictures, the condition of visibility and more. The user can enter the specifications for personal eyepieces for accurate projection of eyepiece fields, and there is a red shading mode for night field use with your laptop. All these features make this celestial atlas more complete than a conventional planetarium program, but also make it more difficult to use. Home Planet is easier to use and has easier to read charts. But one big advantage of Sky Charts is it has a flexible print function, something missing in Home Planet. With Home Planet, you need to print by capturing the screen to a utility such as SnagIt. Sky Charts is available from the French author’s web site at:

http://www.stargazing.net/astropc/

SkyView is a Virtual Observatory on the Internet generating images of any part of the sky at wavelengths in all regimes from Radio through optical to Gamma-Ray. SkyView is available on the Internet at the URL:

http://skyview.gsfc.nasa.gov/

The user tells SkyView the position, scale and orientation desired, and SkyView gives the user an image made to specification. In addition to coordinates, the user can request the image location by a star or other sky object name, and can choose between several levels of input forms. In addition, a Java interface form is available, which I found gave the most appealing images. This site is really more of a photographic tour of the universe than a sky charting planetarium. Some of the images I found , such as the Andromeda Galaxy, were stunning.

Shadows. Looking for a winter project as you wait for the warm spring sun to return? Try building a Sun dial. Shadows is a freeware program that provides all the calculations for making plane sundials. It permits anyone to create a sundial for any location, with any orientation including horizontal or vertical. Shadows gives the user full-size printed plans of the sundial face with all the figures and information necessary to construct the entire dial. It is available from the French author’s web site, where you can also get more info on sundials, at:

http://web.fc-net.fr/frb/sundials/shadows.html