The Precession of the Earth's Axis?

[Pixel]

First of I wish to thank developers for the beautiful program. When i first saw it, i was sure - it is another Lucas shooter . But then when looking closer i found out that despite all eye-candy the planetarium is still precise enough to simulate features that are available only in 2d-professional planetariums. And to go more profesional and still fun, here is my xmas wishlist;)-
1) Precession of the planet's axis.
It is however an important parameter that is missing in planet description. It is importand because it defines the part of the sky which is visible from planet surface at any moment. For example when sitting on Earth in March - year 2500 i was expecting that at the equinox, the Sun will rise from aquarius, not in Pisces like now.
The Earth's rotation axis is not fixed in space. Like a rotating toy top, the direction of the rotation axis executes a slow precession with period of 26,000 years for the entire ecliptic of our planetary bodies to travel around our sun, a trip of 360 degrees. Each one of the 12 signs of the zodiac takes about 2100 years for our solar system to pass through. Every 72 years we actually move backward 1 degree. This was for the public;).

2) Custom time intervals.
there is one very usefull and educational feature with relative small effort to implement. Currently the default time-slice for animation is one second. It will be great if user can change it to whatever other fixed value(per second) say - the planet's day,month,year ..Only in this case we can observe movements that are usually invisible without astronimic measurements. Then we can see yearly movement of Sun over sky, dayly movement of other planets over sky and even star paralaxing.

Congrat's,
Pix.

[Guest]

Use the 'L' and 'K' keys to increase/decrease the time flow rate. Use the 'J' key to reverse the time flow direction. Enjoy!

- Hank

[chris]

I've already got precession working in my development version of Celestia. I use it to model the irregular rotation of the asteroid Toutatis which has two separate rotation periods of 5.41 days and 7.35 days.

--Chris

[Fleegle]

Pixel doesn't want to change the rate at which time passes, he just wants to change the way it is measured. For example, rather than measuring time in Earth years you would be able to measure it in Venus years or whatever length of time you wish. Or if you create a planet with a 14 hour day, you could set the program to a 14-hour clock rather than a 24-hour clock.

I would love to see a feature like this in Celestia.

Fleegle

[Pixel]

I've already got precession working in my development version of Celestia. I use it to model the irregular rotation of the asteroid Toutatis which has two separate rotation periods of 5.41 days and 7.35 days.

--Chris

Great! I don't know if it is applicable to other planets, because long-term precession is very dificult to measure. But at least for the Earth we know it.

[Pixel]

Actually the idea was quite simple and it is even not mine - i saw such a feature in other planetariums. It is just possibility to set the exact animation step. For example if you look at night sky from Earth, you are interested to see what is changed in the sky axactly after 24h:00:00. In animation mode you should see only planents and Moon moving. Of course when you are on Earth, the interested periods are 1min, 1hour, 24hours, one month, one year. If you are on another planet, the interested periods will be different. BTW , i am curious, what is the period , per which a solar system configuration (snapshot) is repeated again?

3) i miss also toggle on/off the ecliptic plane. It can look like semitransprent disk (as lagre in diameter as possible)

Cheers,
Pix

[Pixel]

i am curious, what is the period , per which a solar system configuration (snapshot) is repeated again?

Simply consider the Minimum Common Multiple of all the rivolution period of the planet you would like to consider (I hope you are not so much disturbed excluding asteroids ) including the rotation period of Earth if you want the same snapshot from the same obervation place.

I guess there is and there was and there will be no man on the earth with the same planetary configuration over his head when he born.

[Pixel]

[/quote]
I guess there is and there was and there will be no man on the earth with the same planetary configuration over his head when he born.
[/quote]

Now i have understood why people never repeats

[Sum0]

I don't believe this! I was reading about precession today, and I thought "it's a pity Celestia doesn't support this... I'll post something about it..." only to find someone beat me to it!