Other Downloads for SkyChart III

This page contains some additional files that you can download to enhance SkyChart III. Links to downloadable files, as well as instructions for how to use them, are provided here. These files may all be downloaded free of charge.

Asteroids and Comets

To make sure that SkyChart III provides accurate positions for asteroids and comets, you should use the most current orbital elements possible. The following diagram illustrates the difference between the actual position of the asteroid Ceres, and its position predicted with an out-of-date set of orbital elements (specifically, its orbital elements for 1997 Dec 18.0). As you can see, the error grows dramatically after about 1 year from the epoch of osculation. By two years, Ceres is more than 600 arseconds from its predicted position -- one third the width of the full moon!

The Harvard-Smithsonian Center for Astrophysics has kindly provided sets of current orbital elements for asteroids and comets suitable for loading into SkyChart III. The following files are currently available. (Please note that the links below connect directly to the files on the CfA's web site; to view the original page which contains them, click here):

To download these files, right-click (Windows) or click-and-hold (Macintosh) on any of the above links; then select "Save Target As" (Windows) or "Download to Disk" (Macintosh) from the popup menu that appears. After you've saved the file to your computer's hard disk, start SkyChart III. Select the Import SkyChart Text File command from the File menu, and open the file you just downloaded. SkyChart III will then import the file into its object database; you can remove it later on with the Delete Database File command.

Artificial Satellites

As with asteroids and comets, it's important to use up-to-date elements to make accurate predictions -- orbits no more than 30 days out of date are reccomended. For artificial satellite observers, Dr. T. S. Kelso's CelesTrak.com web site is a good source of current orbital elements. The following links will allow you to download the latest satellite orbit files directly from CelesTrak.com:

Another good source of satellite orbit files is Mike McCant's Satellite Tracking TLE ZIP Files. Quick links to some of the files on this web site are:

All of these files are in standard NASA/NORAD two-line-element format and can be imported into SkyChart III. To do so, right-click (Windows) or click-and-hold (Macintosh) on any of the above links; then select "Save Target As" (Windows) "Download to Disk" (Macintosh) from the popup menu that appears. (The files on the McCants web site are ZIP-compressed archives; you may need a utility program like WinZip (for Windows users) or ZipIt (for Macintosh users) to decompress them.) After you've saved these files to your computer's hard disk and/or decompressed them, start SkyChart III. Select the Import NASA Satellite File command from the File menu, and open the file you just downloaded. SkyChart III will then import the file into its object database; you can remove it later on with the Delete Database File command.

Note: if the objects you imported are not appearing on the screen, the reason is probably that they are fainter than the limiting magnitude for solar-system objects. To change this limit, select the Symbols & Grids command, under SkyChart III's Draw menu. The limiting magnitude for solar system objects is under the section for Draw Planets. You can remove the solar-system-object magnitude limit by deleting the value in this field; then all solar system objects will be displayed, regardless of how faint they are.

Traditional Constellations

The constellation figures depicted in SkyChart III are a modern version based on H.A. Rey's book, The Stars: A New Way to See Them. David Lazaroff has provided a constellation import file which shows the constellations in a more traditional form. These figures are based on the SC001, SC002, and SC003 Constellation Charts in the ESSCO Classroom Publications series from Sky Publishing Company, 49 Bay State Rd., Cambridge, MA 02138-1200. The following images, generated by SkyChart III, are a good example of the differences between H.A. Rey's depiction of the constellations, and the traditional version:

Ursa Major according to H.A. Rey

Ursa Major, traditional depiction

Along with the traditional constellations, we've also provided a "modern" constellation file that generates the constellations according to H. A. Rey (as they appear on the SkyChart III CD-ROM by default). You can use this to restore the constellations to their original appearance after importing the traditional constellations file.

To download these files, right-click (Windows) or click-and-hold (Macintosh) on any of the above links; then select "Save Target As" (Windows) or "Download to Disk" (Macintosh) from the popup menu that appears. After you've saved the file to your computer's hard disk, start SkyChart III. Select the Import SkyChart Text File command from the File menu, and open the file you just downloaded. SkyChart III will then import the file into its object database; you can remove it later on with the Delete Database File command.

You probably want to delete the constellation file that came with SkyChart III by default before importing this new Traditional constellations file; otherwise, you'll get two versions of the constellation figures displayed simultaneously! To do this, use the Delete Database File command to delete the file called Figures.skd inside the Constell folder, inside the Database folder, inside the main SkyChart III application folder.

And, before doing any of this, you might want to make a backup copy of the entire Database folder. That way, you can easily switch between the modern and traditional constellations by using the Open Database command in the File menu.


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This page was last updated on 2 April 2003.