Celestia Forums

I mean, before posting them in the add on page, is there accuracy or quality control to check out if orbits are accurate?

I discovered that Galileo crashes on the atmosphere of the 2 planet it visits. I also had been asked if Pioneer 11 passed so close to Saturn...

Is MIR at the proper altitude or position or even the proper orbit?

I was asked if Saturn could have shadows casted so far to the north as it has right now.

So I ask myself if I can tell people ad ons are reliable, or just something for visual amusement, just an approximate view and not a good material for hardcore fans.

As a rule of thumb, ALL addons ARE NOT accurate.

They are made by amateurs, like you and me. Most users don't have a scientific formation, so the addons they are making cannot be trusted, on a scientific point of view.

Even addons made by scientists contains errors, and are subject to Celestia's limitations. So every addons found on the net are suspect.

I was asked if Saturn could have shadows casted so far to the north as it has right now.

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I suspect that the rings of Saturn and the shadows are reasonably reliable in their configuration and angle. On the other hand such add-ons as exoplanets are subject to a fairly large margin of error, especially in their appearance and orientation; and the fictional add-ons are just for fun, of course.

Don't we have even some basic reliable information on planet axis inclination?

Grant Hutchison spent a lot of time making sure the information in Celestia's solarsys.ssc is accurate. This includes planetary inclinations (Obliquity).

If you find an error, please be sure to post it here on the Forum. Be sure to include the source of your corrected value.

selden wrote:Grant Hutchison spent a lot of time making sure the information in Celestia's solarsys.ssc is accurate. This includes planetary inclinations (Obliquity).

If you find an error, please be sure to post it here on the Forum. Be sure to include the source of your corrected value.

I was told by a guy that shadows of Saturn might not be as shown in Celestia. It seemed strange because obliquity might have been a basic data in the construction of Celestia. So either I must not believe in that guy or I might have to think the authors of Celestia were not serious.

You bet what option I had chosen. I am now questioning the guy... last named Sierra. He claims to be well connected to astronomers in this country, and he claims to know lots so he had been even at conferences, but you bet whoever they are, they are not NASA and since there is no observatory in my country, I doubt they may have better data than the one in Celestia.

So I'm sorry for asking those stupid questions. I just wanted to know if the effort of making Celestia objects was serious other than the eye candy factor. You know... in case of finding more guys like Sierra.

The guy also told me that he wasn't sure Pioneer 11 passed near Saturn or even that close as shown in teh add on. I checked out and Pioneer 11 indeed passed and photographed Saturn on september 1, 1979. If astronomers in this country are like Sierra, they are a bunch of ignorants. I just couldn't confirm how close Pioneer 11 passed near Saturn.

Fortunately I am a complete newbie in astronomy, so I have the right to make stupid questions or stupid statements.

I just found that Mariner 9 took off on May 30, 1971, but the add on shows it already in orbit around Mars by June 1. My guess is such add-on may need some work.

Also, Galileo add-on needs some work for it crashes on Venus and Jupiter.
Most of sats may need to adjust orientation so they beam their data to Earth, or I need orientation to see why these add-ons are right and I am wrong. But since I am just a scifi lover, but a complete newbie in astronomy matters, I can make mistakes... HORRIBLE and stupid mistakes while I learn.

The shadows of the rings of Saturn are accurate. They can be compared with the pictures being taken by Cassini.

The xyz trajectories of probes like Galileo often do not specify the probes' locations frequently enough during planetary flybys. Celestia interpolates between the points that are specified in the trajectory. The probes' orbits change quickly and by large amounts during the gravity assist flybys, so when there are not enough locations specified, Celestia cannot draw them in the correct places.

Did you check to see what year the Mariner 9 Addon specifies? Apparently Mariner 9 arrived at Mars on November 14, 1971, and orbited Mars for about a year, so June, 1972, would have been OK . Or 1971 might have been a typo.

Unfortunately, Celestia does not yet really provide a way to make sure that the radio antennas of space probes point in the right directions.

Probes could just change orientation somehow, to aim to a general region where Earth could be. What I find inaccurate is to have Voyager aiming antena to north pole...

Is there a way or app to graphically draw trajectoies in Celestia?
I might like to correct the buggy probe, but unfortunately I can't.

Jack's site has a high detail Galileo xyz file. http://homepage.eircom.net/~jackcelestia/

You don't need to change the trajectory, just the orientation of the probe. I think you can make it always point in the general direction of the sun, which probably is good enough for when it's a long way away.

To do this, you'd have to define correct values for the probe's RotationPeriod (6 years or so), Obliquity and RotationOffset.

Hmm. You might need to make several different SSC entries for the probe, a different one for each of the flybys. You can use Beginning and Ending directives to make the different versions of the probe (with different orientations) visible at the correct times.

Does this help?