Celestia Forums

Does v. 1.3.1 Include the earth's precession? I want to use the program to get ancient skycharts and it does not appear that the precession is accounted for. If not can anyone tell me how I could plug this little(but important) detail in? Thanks

Pick wrote:Does v. 1.3.1 Include the earth's precession? I want to use the program to get ancient skycharts and it does not appear that the precession is accounted for. If not can anyone tell me how I could plug this little(but important) detail in? Thanks

dunno about 1.3.1, but 1.4.0pre5 doesn't appear to include it. I can park at the north pole look up, ff time by thousands of years, and I'll still be looking at Polaris...

Pick wrote:Does v. 1.3.1 Include the earth's precession?

The last time I saw discussion on this (some long time ago) Celestia did not include precession.
The experiment by EDG seems to indicate that it is still not included

I want to use the program to get ancient skycharts

If it is just charts that you want then you could have a look at the freeware "Cartes du Ciel", page in English at :-
http://www.stargazing.net/astropc/index.html
It includes planetary info between -3000 and +3000 (so I would hope precession is included !!) according to the methods of Steve Moshier http://www.moshier.net/index.html
I have not tested it that far back! I just use it as an excellent bit of kit for current amateur astronomy with a 6inch home made Newt.

If not can anyone tell me how I could plug this little(but important) detail in? Thanks

No idea, sorry ! (try a 'feature request' in the sticky at the top of this forum ??)

It is interesting to note here that thanks to precession there are currently thirteen zodiac constellations! The thirteenth one that has joined in is Ophiuchus, the serpent bearer.

Michael Kilderry

Michael Kilderry wrote:It is interesting to note here that thanks to precession there are currently thirteen zodiac constellations! The thirteenth one that has joined in is Ophiuchus, the serpent bearer.

The pages below are quite interesting in this regard:
http://www.griffithobs.org/IPSrealrealc ... tions.html
http://www.griffithobs.org/SkyOphiuchus.html

It's quite nifty to go look at where the sun was (as viewed from Earth) when you were born in Celestia. All this time I thought I was a Libra, I'm really a Virgo!

Hey, I am an Ophiuchus !

Celestia does support precession, but it's not enabled for Earth. The reason is that the orbits of moons are specified with respect to the equatorial plane, so when this plane precesses, the moon ends up in the wrong position. Soon, I hope to implement options for other reference planes and then turn on precession for the Earth. You can see precession working if you visit the asteroid Toutatis or Saturn's moon Hyperion (where precession is used to approximate its chaotic rotation.)

--Chris