Celestia icon indicating copy to clipboard operation
Celestia copied to clipboard

Globular clusters appear as red points from a distance

Open SevenSpheres opened this issue 4 years ago • 13 comments

In Celestia 1.7 many (all?) globular clusters are visible from the Solar System as reddish points. In Celestia 1.6.1 this is not the case. I'm not sure if this is actually a problem.

View towards the galactic center from Sol in 1.6.1: mwcenter-161 and in 1.7.0: mwcenter-170 I notice the Milky Way also looks different between these two images; I have no idea why.

SevenSpheres avatar Nov 21 '19 01:11 SevenSpheres

Come to think of it, the typical GC model also looks too circular and feels small to the eye. Maybe there should be several variants or models of GC's based on their diameter, mass and star count.

LafuenteAstronomy avatar Nov 23 '19 22:11 LafuenteAstronomy

Agreed.

Anthony-B-Russo10 avatar Nov 23 '19 23:11 Anthony-B-Russo10

Come to think of it, the typical GC model also looks too circular

They're called "globular" clusters for a reason.

and feels small to the eye. Maybe there should be several variants or models of GC's based on their diameter, mass and star count.

The CoreRadius and KingConcentration parameters change the appearance of GCs. Try looking at lots of them, they do look different. What Celestia does need is better galaxy rendering (as Celestia.sci has implemented).

SevenSpheres avatar Nov 23 '19 23:11 SevenSpheres

They're called "globular" clusters for a reason.

I meant that they look too circular and not spherical, since though the model is 3D, it isn't fully rendered to the point it actually looks like a sphere. Besides, a few globular clusters don't really look spherical at all, such as Mayall II and Omega Centauri, which look more ellipsoidal (Which makes sense, as both of them are remnants of the galactic cores of dwarf galaxies that were cannibalized by the Andromeda and Milky Way Galaxies respectively), and Palomar 1 and Djorgovski 1, which look too dispersed and therefore, somewhat lacks a proper spherical structure

LafuenteAstronomy avatar Nov 29 '19 14:11 LafuenteAstronomy

The CoreRadius and KingConcentration parameters change the appearance of GCs. Try looking at lots of them, they do look different.

Well, honestly, it didn't feel that way to me. I do think the models themselves can be improved, or better yet, perhaps add some stars just enough to make it have a population

What Celestia does need is better galaxy rendering (as Celestia.sci has implemented).

To that I agree. Current galaxy rendering is so dull at normal ambient, but increase the brightness, and it will become too bright. What can be done is to improve the default galaxy model to be even better than it is now, and include several features per galaxy type, like H II regions, dusts, gases, stellar population colors, etc

LafuenteAstronomy avatar Nov 29 '19 15:11 LafuenteAstronomy

@LukeCEL can't reproduce this issue - it may be Windows-specific.

SevenSpheres avatar Nov 30 '19 00:11 SevenSpheres

Another view (look closely).

Milky Way in 1.6.2: mw-162 Milky Way in 1.7.0: mw-170 A crop of the above image. See the little red dots? redglobulars

SevenSpheres avatar Apr 07 '20 20:04 SevenSpheres

With Celestia 1.7.0 + Origin, the same bug can be seen at the Andromeda Galaxy (just look at the full size image):

m31-globular-bug

SevenSpheres avatar Apr 24 '20 21:04 SevenSpheres

Hi everyone,

After a closer look it appears that these red dots do appear on macOS as well. globclus

They are very hard to see — much less conspicuous than the picture that @SevenSpheres posted. They also appear and disappear when you change the view, much like the twinkling galaxies bug I described in #544.

LukeCEL avatar Apr 25 '20 00:04 LukeCEL

Same issue on Android.

Screenshot_20200518-102512

SevenSpheres avatar May 18 '20 16:05 SevenSpheres

I notice the Milky Way also looks different between these two images; I have no idea why.

Well, now I know that this is because galaxy sprites are randomly generated (see e.g. #1160).

SevenSpheres avatar Dec 26 '21 22:12 SevenSpheres

@SevenSpheres is this still valid? I remember @levinli303 made a fix for this or similar issue.

375gnu avatar Nov 22 '22 13:11 375gnu

The issue is still present, but at least for me is less visible - more like LukeCEL's screenshot here.

SevenSpheres avatar Nov 22 '22 16:11 SevenSpheres