Celestia Forums

I haven't seen many post on this. So I would like to congratulate the developer for this new feature in Celestia. It works very well.

I have a question and enhencement suggestions :
1/ Why is there no eclipse calculation for all moons of jupiter/saturn but only the biggest ones ?
2/ Is it possible to give more detail on the eclipse ? (time enter in shadow, exit, first contact, last contact, total/annular, etc...)
3/ Would it be possible to have the same calculation for any Star system ?

4/ A new feature would be calculations of star occulations from a given planet by any given body.
5/ Another one is calculation of oppositions & conjonctions & transit with regard to a given body
6/ aphelie and perigee calculations
7/ in 2 words a comprehensive ephemeris

I know, this is a lot of work, but the current Eclipse finder is so cool and it is one of the most difficult feature to do. Now remain the easiest ones!!!
(just few words for encouragement)

Thanks again
---Paul

1 - None of the minor moons would create an eclipse.
3 - Why? It's not possible to have eclipses in any of the extrasolar systems.
2, 4, 5, 6, & 7 - That'd be more work than it would probably be worth it. Stick with the KISS principle I say.

Thanks Chris, the eclipse finder is the best new addition!

Aya Reiko wrote:3 - Why? It's not possible to have eclipses in any of the extrasolar systems.

how is it not possible? i mean i understand that they wouldnt be acurate because we dont know the exact orbit patterns, but what about custom made solar systems? i know i would like it to work for mine. and one more thing what about an alignment finder for 3 or more planets with teh parent star? that would be really nice.

Aya Reiko
I disagree with you
1/ most (likely all) of the minor moons can be eclipsed by the planet (tho they won't eclipse the sun)
2/ most of the work has already been done by calculating the time of the eclipse, so the remaining information I asked should not be that difficult. (however the first contacts times depends on Lat and Long)
4 5 6 / Most planeterium programs do that, I think Celestia also deserves these features. It'll have it all!!!

Moreover, I recall that this Finder Eclipse was developed by somebody else than Chris. And I'm sure he'll be willing to work on these additions.
Could you just remind me his name in order to give him the credits ?
Thanks
---Paul

billybob884 wrote:

Aya Reiko wrote:3 - Why? It's not possible to have eclipses in any of the extrasolar systems.

how is it not possible? i mean i understand that they wouldnt be acurate because we dont know the exact orbit patterns, but what about custom made solar systems? i know i would like it to work for mine. and one more thing what about an alignment finder for 3 or more planets with teh parent star? that would be really nice.

No data

I'm glad to hear that people are trying out the Eclipse Finder. Most of the code was not written by me, but by another Celestia forum contributor, Kendrix.

The eclipse finder will be enhanced in future versions of Celestia. Certainly, I want to make it more general so that it can be used for calculating eclipse events between any planet/satellite system. In fact, the eclipse finding code already is quite general. But developing a user interface for it will require some time.

I would like to maintain the current focus of Celestia as a visual simulation. There are other programs that handle calculating star occultations (for example) quite well, so I'm not all that interested in adding such a feature to Celestia. Also, since Celestia ignores light time delay, it's timing calculations for such events wouldn't be very accurate.

To sum things up, you'll definitely see items 1, 2, and 3 addressed in Celestia 1.2.6. The other things will have to wait until I'm satisfied enough with the rendering capabilities of Celestia to devote more time to ephemeris features--in order words, quite a while. Of course, if someone else were to take it upon him or her self to write an ephemeris package, complete with a nice UI and integration with Celestia, it could happen sooner

--Chris

Rassilon wrote:

billybob884 wrote:

Aya Reiko wrote:3 - Why? It's not possible to have eclipses in any of the extrasolar systems.

how is it not possible? i mean i understand that they wouldnt be acurate because we dont know the exact orbit patterns, but what about custom made solar systems? i know i would like it to work for mine. and one more thing what about an alignment finder for 3 or more planets with teh parent star? that would be really nice.

No data

what exactly do you mean by no data?

billybob884 wrote:

Rassilon wrote:

billybob884 wrote:

Aya Reiko wrote:3 - Why? It's not possible to have eclipses in any of the extrasolar systems.

how is it not possible? i mean i understand that they wouldnt be acurate because we dont know the exact orbit patterns, but what about custom made solar systems? i know i would like it to work for mine. and one more thing what about an alignment finder for 3 or more planets with teh parent star? that would be really nice.

No data

what exactly do you mean by no data?

In order to have an eclipse, a world needs to have a moon.

I think perhaps you're being a little too limited in your definition of eclipse. Strictly speaking an eclips happens whenever one object casts a shadow on another one. If Celestia generated "real" shadows, then they'd happen naturally. Unfortunately, like my own dream of star movement, the amount of raytracing involved would slow things down unacceptably in most circumstances.

Aya Reiko wrote:

billybob884 wrote:

Rassilon wrote:

billybob884 wrote:

Aya Reiko wrote:3 - Why? It's not possible to have eclipses in any of the extrasolar systems.

how is it not possible? i mean i understand that they wouldnt be acurate because we dont know the exact orbit patterns, but what about custom made solar systems? i know i would like it to work for mine. and one more thing what about an alignment finder for 3 or more planets with teh parent star? that would be really nice.

No data

what exactly do you mean by no data?

In order to have an eclipse, a world needs to have a moon.

wouldnt a planet be able to cast a shadow onto another planet?

all planets have cone shadows behind them, since of course their star is much larger than the planet. so two planets would have to be extremely close for one to fall into the cone of darkness behind the other.

Thanks to you Calculus for your compliments on my eclipse finder...

But thanx to Chris for this wonderful Celestia !!!

I wan't wait for the next version !

erostosthenes wrote:all planets have cone shadows behind them, since of course their star is much larger than the planet. so two planets would have to be extremely close for one to fall into the cone of darkness behind the other.

what about custom made solar systems that have moons?

billybob884 wrote:

erostosthenes wrote:all planets have cone shadows behind them, since of course their star is much larger than the planet. so two planets would have to be extremely close for one to fall into the cone of darkness behind the other.

what about custom made solar systems that have moons?

Your missing the point...The eclipse finder to my knowledge goes on data thats been recorded in the past/or a probable future event...eg: Io eclipses Jupiter has been recorded to happen at a certain time...Any extrasolar moons are theroy at best...No moon/planet outside of our solar system has been seen to eclipse another...thats why its not listed in the eclipse finder

Well, gee, to the extent that Celestial bodies travel on simple ellipses, in principle it's just a matter of solving the appropriate systems of equations. Unlike a many-body gravitational problem, an analytic formulation might actually be possible.

But not easy. *I'm* certainly not going to try!

No Rassilon you're wrong.

The eclipse finder REALLY compute to find eclipses...

I have limited it to the solar system but with minor changes chris could make it usable in every system !

selden wrote:Well, gee, to the extent that Celestial bodies travel on simple ellipses, in principle it's just a matter of solving the appropriate systems of equations. Unlike a many-body gravitational problem, an analytic formulation might actually be possible.

But not easy. *I'm* certainly not going to try!

The motions of solar system bodies are in general not modeled very well by simple ellipses. Perturbations from other objects are significant, and essential to account for when computing eclipse times. The eclipse finder uses a brute force technique for finding eclipses; it computes positions of bodies at fixed intervals over a time range, and at each time checks for an eclipse. It should be possible to refine this using an adaptive time step, but an analytic solution is out of the question. Remember that 'orbits' in Celestia can be a series of arbitrary samples (e.g. the Voyager 1 and 2 trajectories.)

--Chris