Twinkling stars without atmosphere

[Mario Di Maggio]

Apologies that I am submitting this request as a bug (but I cannot see a section for 'requests').

I have already discussed this issue with a few of the developers and I understand that currently it is not possible to keep the stars twinkling with atmosphere turned off (as in previous Stellarium versions).

I understand that this is the way it is in nature; the night sky is never truly black; etc, etc.

YET I ask that you please consider this issue from a practical teaching perspective inside a portable planetarium:

(1) Most portable planetarium projectors do not have good dark levels (contrast ratio). So even with Zodiacal light off, light pollution at zero and atmospheric extinction at zero, the Stellarium sky does NOT look dark. It may look dark on your computer screen, but it is most certainly NOT dark inside the majority of portable planetariums.

(2) And when it is full Moon, then in a planetarium with an average quality projector the sky looks absolutely terrible. In fact, the night sky looks very, very unrealistic (which is exactly the opposite of what Stellarium is trying to achieve).

Yet this problem could be solved very easily if the user had the option of turning off the atmosphere AND keeping the stars twinkling.

Now I am not a programmer and have no idea how difficult this is to implement. It could be that your current code design makes such a function very difficult - in which case I understand your reluctance to introduce 'stars twinkle with no atmosphere'.

Yet if it is relatively easy to do, then I strongly encourage you - on behalf of the thousands of portable planetarium operators who want to show their audiences a realistically dark sky - to please consider introducing it in the next version.

Thanks very much.

Mario

[Alexander Wolf (alexwolf)]

A fix has been committed as revision 8654 of the trunk branch in Stellarium's Bazaar repository at Launchpad:
http://bazaar.launchpad.net/~stellarium/stellarium/trunk/revision/8654

I've introduced a new option in config.ini file - stars/flag_forced_twinkle=(false|true) - for planetariums to enable a twinkling of stars without atmosphere.

[Mario Di Maggio (domeclub)]

Thank you Alexander and the Stellarium team, you guys are STARS - bright, constantly twinkling stars!! :-)

[Alexander Wolf (alexwolf)]

Fix has been synced: http://bazaar.launchpad.net/~stellarium/stellarium/0.15/revision/8589

[Mario Di Maggio (domeclub)]

Hello

I've just installed the new ver. 0.15.1 and the config.ini file does not include:

"...new option in config.ini file - stars/flag_forced_twinkle=(false|true) - for planetariums to enable a twinkling of stars without atmosphere"

This is quite disappointing because from the above discussion I thought it was going to be included in the new release.

I and the 20,000 annual visitors in my mobile planetariums were VERY much looking forward to it :-((

[Alexander Wolf (alexwolf)]

Sorry, but why you do not added stars/flag_forced_twinkle=true in config.ini just? ;)

[Mario Di Maggio (domeclub)]

BRILLIANT!! I did it and it works!! Thank you, thank you and thank you again. I will let everyone know and the mobile planetarium community will be SO grateful.

Thank you Stellarium development team, you are AWESOME.

[Mario Di Maggio (domeclub)]

Hello - yes, it's me again (sorry :-)

My portable planetarium audiences and I have been enjoying a truly dark Stellarium sky (with atmosphere off) PLUS beautiful twinkling stars.

Thank you again for including this option in the config.ini file.

YET unfortunately now children ask the questions: Where are the shooting stars? Can we please see a shooting star?

Would it be too much trouble to request that you please include the option to maintain shooting stars with atmosphere off?

Please let me know if you would consider doing this and if you would like me to open a request as a new thread? (and where I should do so?)

Thanks very much in anticipation of a dark Stellarium sky WITH shooting stars :-)

Regards

Mario

[Alexander Wolf (alexwolf)]

I've introduced a new option in config.ini file - astro/
flag_forced_meteor_activity=(false|true) - for planetariums to enable a show of sporadic meteors activity without atmosphere.

Will be available for testing in next beta.

[Mario Di Maggio (domeclub)]

Alexander you're unbelievable, thank you SO MUCH

[Mario Di Maggio (domeclub)]

Hello everyone. I've just installed ver. 0.22.2 and it looks great in my mobile planetarium dome.

I've updated my confid file with the new bespoke settings above, and everything is looking good ... except for one thing .... something completely new I've never experienced before:

Now I see LESS stars when I remove the atmosphere (?!)

It's really weird, and I can't see what settings I need to change to fix this - but weirdly, there are LESS visible stars when I remove the atmosphere.

This is OK if the Moon is not in the sky - but on moonlit nights I have to remove the atmosphere to make the sky darker ... and it becomes darker .... but with LESS stars!

Can anyone please explain why this is happening in ver. 0.22.2?

Thanks very much.

Mario

[Alexander Wolf (alexwolf)]

Please check the installed star catalogs

[Mario Di Maggio (domeclub)]

I've installed a few more catalogues (up to and including catalogue 7 of 9). Yes there are now more stars visible if I increase the Limit Magnitude value in the Stellarium Remote Control.

YET, when I remove the atmosphere, I still see less stars.

It appears to be because ALL the stars become dimmer when I remove the atmosphere (even the really bright ones).

Which setting is causing the stars to dim when the atmosphere is removed I wonder?

Or could it be this bespoke function is not working correctly in ver. 0.22.2? :

[stars]
flag_forced_twinkle = true

[Alexander Wolf (alexwolf)]

Please check settings for absolute and relative scales for stars.

P.S. Configs between series 0.15 and 0.22 are very differ

[gzotti (georg-zotti)]

This is a tricky point. The sky (atmosphere) model has a default background brightness even when the atmosphere is switched off, so that the visibility algorithm can work. For some reason (I think I added the "TODO: explain" a few years ago...), it seems that if we switch off the atmosphere, the sky is brighter (no absorption?) than in the darkest night with atmosphere. Therefore probably stars are subdued somewhat stronger.

We are certainly putting much more effort into creating a realistic sky than into a flickering sky without refraction and other atmospheric effects. Wait until the next release and you won't want to switch off the atmosphere ever again. Other than that, yes, please adjust your relative and absolute star scales. You can also develop two mini-scripts (3 lines each) to

1) switch off atmosphere and adjust star scales
2) switch on atmosphere and re-adjust star scales to default values.

Configure these scripts to be run via hotkey.

[Mario Di Maggio (domeclub)]

> Configs between series 0.15 and 0.22 are very differ

I see. Can you please let me know in which version did you change the way the atmosphere behaves?

> Wait until the next release and you won't want to switch off the atmosphere ever again.

That sounds great. Yet because in a planetarium the screen is round, there is much cross-reflection (and 'amplification') of light. It's hard to believe on a moonlight night the sky can remain black with the atmosphere turned on! :)

Turning off the sky, as was possible in ver. 0.15, created a BEAUTIFUL black sky full of twinkling stars.

I think it will be best for me to go back to an older version, where the sky behaviour was different.

Which was the last version where the atmosphere behaved in a simple way?

Thanks very much

[gzotti (georg-zotti)]

These were about 7 years with about 4 releases per year. Please see ChangeLog in the Windows programs/stellarium menu, or just check them. I have no time for such software archaeology in these weeks, sorry.

[Mario Di Maggio (domeclub)]

No problem, thank you for all your help and advice. I have gone back to ver. 0.19.3 - and the sky with no atmosphere is pitch black again, full of stars. Just perfect for my mobile planetarium - and so much better now with a 4K projector :)

I realise in the future I will need to install a more current version of Stellarium - but I'm hoping by then there will be MORE stars when the atmosphere is removed, not LESS :)

Thank you again for the most wonderful astronomy application in the world!

Regards

Mario