Solar System Observer

[RF52]

Expected Behaviour

Actual Behaviour

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Steps to reproduce

System

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• Operating system: <Name, version number>
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[RF52]

Hi,

I've been using Stellarium for a while, and have recently run into an issue that I can't resolve. I'm looking at the Galilean satellites, to compare my telescope observations with Stellarium predictions. Part of this involves creating an "overhead view" of Jupiter to show the position of the moons in their orbits. I am finding an inconsistency, which is described in the following example.

The image above shows the Stellarium prediction for midnight on June 21 2019.

This next image above shows one of my telescope captures, which seems to agree nicely.

The image above is the "Solar System Observer" view from Stellarium, which appears incorrect. The Earth on this image is situated to the bottom left of Jupiter (at an angle of about 50 degrees to the "vertical"), and from this perspective, the three visible moons all appear to "the left" of Jupiter, whereas the first two images above suggest that Europa is to the left, and Callisto & Ganymede are to the right.

I suspect I am doing something wrong, but have read all the posts I can find, but to no avail. Can someone help me please?

Roger. (Windows 10, Stellarium (0.18.2))

[gzotti]

To allow a near-orthogonal view, the Solar System Observer is located very far from the sun, so that light travel time becomes an issue. I also had fun with a Lunar eclipse. To compare with Earth view, it's better to switch off light time correction and accept a temporal mismatch of the ~45 minutes from Jupiter to Earth.

[RF52]

Thank you for that prompt response gzotti. I hadn't realised SSO was so far distant. Ive tried creating a new observing point in the ini file:

[ jupiter_observer ] name = Jupiter Observer parent = Jupiter albedo =0. color =0. , 0., 0. halo = false hidden = true coord_func = ell_orbit orbit_AscendingNode =0 orbit_Eccentricity =0 orbit_Epoch =2451545.0 orbit_Inclination =90 orbit_LongOfPericenter =0 orbit_MeanLongitude =90 orbit_Period =70000000000 orbit_SemiMajorAxis =14000000 radius =1. rot_obliquity =90 type = observer

but sadly I still cannot get it to generate an image compatible with the observations and "normal" Stellarium view from my observing point. The new observing point works, but even by time shifting by quite a lot, it is not making a lot of sense to me.

I have placed Jupiter Observer 100 x Jupiter diameter above its North pole (at least I think I have).

R.

[gzotti]

hmm, 14.000.000 km are roughly 1/10 AU. Increase this again by 50 and you have 5AU, resulting in roughly the same light time delay as for earth-bound observers.

[RF52]

Arghh - I am a fool! It is surprising how often writing a problem down leads to its solution. I made an error and had assumed Io was behind Jupiter, rather than in front.

Jupiter Observer now seems to work a treat!

As a matter of interest, making the distance 1,400,000 Km resulted in significant distortion of the orbit paths, but 14,000,000 gives a very acceptable image - below.

It compares well with my earlier prediction when you remember that Earth lies to the "bottom left" of the Stellarium image:

Very many thanks for your input.

R.

[gzotti]

I think I will add this Jupiter Observer to our default list :-) Thanks for the suggestion.

[RF52]

Please do so, you're welcome.

BTW one interesting and very neat behaviour of Stellarium, which I didn't expect, is that if you lock onto a target, Jupiter, using your default Earth based viewing location, freeze the display motion and specify a time, and then if you select the Jupiter Observer location, Stellarium updates your chosen time to allow for the speed of light. At least, I think that's what's happening.

I'm assuming since Jupiter is a SSO then the "compensate for speed of light" option is observed (if you've got it ticked), then assuming the Jupiter Observer in NOT a SSO, the light speed won't be invoked BUT instead your viewing time is altered to allow for it. (In my case the time moved back by just over an hour - I tried it several times.)

R.

[gzotti]

@RF52 Your observations around time are governed by timezone handling in the site panel. Only terrestrial sites have timezones. In the status bar (bottom of the screen) you see the time offset as UTC+xx. Should be UTC+00:00 for extraterrestrial sites, unless you choose a timezone manually.

[alex-w]

Please check the latest beta

[RF52]

Hmm. I've never checked Beta's before! However, I've downloaded:

https://github.com/Stellarium/stellarium-data/releases/download/beta/stellarium-0.19.1.17106-win64.exe

and I get the message "The setup files are corrupted. Please obtain a new copy of the program."

Not sure what's wrong? I've tried 3 times.

[alex-w]

@RF52 thanks for report about problem for package! I've fixed it - please check it again.