Green Halos around stars

[Frank Paulic]

The RGB and subsequent images has green halos around many stars. I discovered after comparing the R, G and B masters, that the stars in the green masters are larger than the other two.

The stars in RGB that doesn't have the green halo, all the Masters have the same size stars. The RGB are 2x2 binned. Perhaps the seeing wasn't as good for green as compared to the red and blue.

Is there a process in PI that address this? Didn't see anything on the web for this, only for reducing overall halo.

If you overlap the Green Master over Blue Master (or Red), you can clearly distinguish between the green large size as compared to blue (ctrl+page down).

 

[cloudbait]

The RGB and subsequent images has green halos around many stars. I discovered after comparing the R, G and B masters, that the stars in the green masters are larger than the other two.

The stars in RGB that doesn't have the green halo, all the Masters have the same size stars. The RGB are 2x2 binned. Perhaps the seeing wasn't as good for green as compared to the red and blue.

Is there a process in PI that address this? Didn't see anything on the web for this, only for reducing overall halo.

If you overlap the Green Master over Blue Master (or Red), you can clearly distinguish between the green large size as compared to blue (ctrl+page down).

View attachment 21379

Not native, but BlurXTerminator will correct this. For native processes, you could try applying a very mild erosion filter to just the green data. Do you take all your images with one filter and then move on to the next? If so, I'd suggest taking your filtered images sequentially, moving the filter between each exposure. That way you will end up with all your stars the same size across all the channels, even if the seeing is variable.

 

[Frank Paulic]

Thanks, l‘ll try the BlurX on the green. Yes, I use one filter at a time. On my next image, I’ll set the auto exposure in MaximDL to change filters subsequently. That's good advice.

 

[cloudbait]

Thanks, l‘ll try the BlurX on the green. Yes, I use one filter at a time. On my next image, I’ll set the auto exposure in MaximDL to change filters subsequently. That's good advice.

If you use BlurX I'd use it on the RGB image, not a single channel. If you use an erosion filter, just use it on green.

 

[Frank Paulic]

I’ll try the Morphological Process on the green first.

 

[cloudbait]

I’ll try the Morphological Process on the green first.

To be clear, the erosion operation is found in the Morphological Process.

 

[Frank Paulic]

Looks promising, I applied Morphological Process to the Green Master and the stars shrunk down to same size as the R&B Masters. Now don’t see the obnoxious green halo around stars In the RGB combination. Another tool in my back pocket. Thanks for helping me on this Chris.

 

[Frank Paulic]

I would like to inform that applying Morphological Process to the Green Master lead down a rabbit hole with color calibration. The BlurX on the RGB image works, followed by SPCC.

 

[cloudbait]

I would like to inform that applying Morphological Process to the Green Master lead down a rabbit hole with color calibration. The BlurX on the RGB image works, followed by SPCC.

For those without BX, it might be interesting to apply SPCC, separate the channels, apply erosion to the green channel, then recombine.

 

[Frank Paulic]

I got my sequence wrong, after RGB combine, I applied DBE followed by SPCC and then applied BlurX, as one of the methods Chris recommended. This took care of those green halos around stars.

What I also learned in this lesson, is that I used the methodology from the article written in Light Vortex Astronomy for applying DBE. This gave me the best results than all the other on-line videos I came across for DBE. See part three in https://www.lightvortexastronomy.co...-combination-and-further-post-processing.html

 

[cloudbait]

I got my sequence wrong, after RGB combine, I applied DBE followed by SPCC and then applied BlurX, as one of the methods Chris recommended. This took care of those green halos around stars.

What I also learned in this lesson, is that I used the methodology from the article written in Light Vortex Astronomy for applying DBE. This gave me the best results than all the other on-line videos I came across for DBE. See part three in https://www.lightvortexastronomy.co...-combination-and-further-post-processing.html

I always apply SPCC then BX, then DBE if necessary. My experience with applying DBE first is that it either messes up the color, or it doesn't make any visible difference. So I avoid doing it. I think the problem is that it damages the color balance of the stars. That is, after DBE, two stars with the same RGB values before its application will be different afterwards. What's SPCC supposed to do with that?