Stellar magnitude and color ranges seem "flattened".

General discussion about Celestia that doesn't fit into other forums.
Topic author
Yarlan Zey
Posts: 4
Joined: 27.05.2018
With us: 6 months 15 days

Stellar magnitude and color ranges seem "flattened".

Post #1by Yarlan Zey » 27.05.2018, 08:28

It's possible that I'm mis-remembering how Celestia has looked in the past, and it's been a while since I last looked at it. But when I look at it now, the range of magnitudes seems to be "flattened", so that bright stars don't stand out as much as they do IRL. For instance, in the following Celestia screengrab of the region between the Hyades and the Pleiades, those two asterisms barely seem to stand out against the background of dimmer stars. Aldebaran does seem a bit brighter, but again to a much lesser extent than I expect. I notice, too, that nearly all the stars seem to be plain white. The faintest visible magnitude in the Celestia screenshot, if memory serves, is around 10, and it is true that the magnitude variations seem to show up better if I lower the magnitude sensitivity to about 8, which is about as faint as my camera was able to pick up, and even more so if I lower it further still to 6. However, the problem then becomes that all the star images seem too faint and difficult to see. That might be a problem with my computer, but I really don't know.

Celestia Screenshot


By contrast, in the following image which I took myself, the Hyades and Pleiades really stand out against the background. (Note: I used Photoshop and the third-party action kit Astronomy Tools to reduce ISO noise, compensate for light pollution, and add the diffraction points. This tool also made it possible to turn up the color saturation, so the star colors are highly exaggerated but I believe they are mostly correct regarding the qualitative aspect of the colors.) The focal length, exposure, aperture, and ISO are 18, 4s, 3.5, and 500.

My own photo of roughly the same region.

With regard to the colors in the Celestia image, is there some setting I have inadvertently changed to remove nearly all the saturation in the display?

Topic author
Yarlan Zey
Posts: 4
Joined: 27.05.2018
With us: 6 months 15 days

Post #2by Yarlan Zey » 16.11.2018, 23:37

Here's a more recent photo of the Pleiades, taken with with a faster 50mm lens at ~f/2.5, ISO 3200, 4" exposure. Again, the resulting original JPEG image was post-processed as described above to improve contrast and overall appearance.

Link

In this image you can find stars that go all the way down to ninth magnitude and possibly even fainter. The variations in apparent brightness are quite evident here. FTR that's a meteor trail to the left.

How can I make the Celestia display look like this?
Last edited by Yarlan Zey on 17.11.2018, 04:31, edited 1 time in total.

pirogronian
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Post #3by pirogronian » 17.11.2018, 03:22

Probably it is impossible. Solution may be additional renderer parameter.

Topic author
Yarlan Zey
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Joined: 27.05.2018
With us: 6 months 15 days

Post #4by Yarlan Zey » 17.11.2018, 03:40

pirogronian wrote:Probably it is impossible. Solution may be additional renderer parameter.

Do you mean ticking one or more additional boxes in the render options, or something else that the developers would have to build into the product?

pirogronian
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With us: 11 months 6 days
Location: Wrocław

Post #5by pirogronian » 17.11.2018, 09:48

Yes. For example, float magnitude enhacement parameter. I'm one of developers, but I poorly know renderer code, so it may take some time. It would also be accepted by @onetwothree.

onetwothree
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Post #6by onetwothree » 17.11.2018, 17:15

Upcoming 1.7.0 release has a new option to display "black body" colours, so this issue is solved.

Topic author
Yarlan Zey
Posts: 4
Joined: 27.05.2018
With us: 6 months 15 days

Post #7by Yarlan Zey » 21.11.2018, 04:41

Thanks, I'll be looking out for that.


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