Data Source

[Guest]

Hello all. First off, I just discovered Celestia and I'm loving it! Thank you for such a wonderful app!

I decided to contribute back to the project by creating the rings for Neptune, and I'm almost done. I'm getting my data from http://nssdc.gsfc.nasa.gov/planetary/factsheet/nepringfact.html.

While I was there, I started looking around solarsys.ssc and the minormoons addon to see how things were done, but I found several descrepancies<sp?> between the data for Celestia and the data I found at NASA:

http://nssdc.gsfc.nasa.gov/planetary/factsheet/neptunefact.html
http://nssdc.gsfc.nasa.gov/planetary/factsheet/neptuniansatfact.html

For example, Neptune's radius is shown as 24764 on the website, but it's 25225 in solarsys.ssc. Also, Triton's Inclination is off by about half a degree.

I'm not trying to be critical, but I am curious about where Celestia's data came from. Is there another source Celestia used which is more accurate than these pages, or could our data be out of date? If it's the latter, I'd be more than happy to provide an updated Neptune section for solarsys.ssc, especialy since I'm modifying it for the rings anyway.

Thanks again for all your hard work on Celestia.

Troy Corbin Jr.
http://knights.sourceforge.net

[chris]

While I was there, I started looking around solarsys.ssc and the minormoons addon to see how things were done, but I found several descrepancies<sp?> between the data for Celestia and the data I found at NASA:

http://nssdc.gsfc.nasa.gov/planetary/factsheet/neptunefact.html
http://nssdc.gsfc.nasa.gov/planetary/factsheet/neptuniansatfact.html

For example, Neptune's radius is shown as 24764 on the website, but it's 25225 in solarsys.ssc. Also, Triton's Inclination is off by about half a degree.

I'm not trying to be critical, but I am curious about where Celestia's data came from. Is there another source Celestia used which is more accurate than these pages, or could our data be out of date? If it's the latter, I'd be more than happy to provide an updated Neptune section for solarsys.ssc, especialy since I'm modifying it for the rings anyway.

Thanks again for all your hard work on Celestia.

Most of the data on the planets came from appendices in the book _Solar System Dynamics_ . . . It's possible that the NASA data is more accurate. I now have a copy of the US Naval Observatory's 2002 Astronomical Almanac, which should have the most accurate current estimates for physical parameters of solar system bodies. Any adjustment to data in solarsys.ssc will be based on figures from that book.

Also, the Keplerian elements for most of the major solar system bodies in solarsys.ssc are not actually used. Much more accurate custom calculations are used for the the nine major planets and the large satellites of Earth, Jupiter, Saturn, and Uranus (I'll get to Phobos, Deimos, Triton, and Charon eventually . . .)

--Chris

[Troy]

Thanks for the info, and all your hard work.