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jimthompson

Some colour issues with SLL 3.3

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jimthompson    18

Hi All,

I have not had an opportunity to use my SX cameras much over the past 6-8 months but finally had a chance over the past couple weeks.  I have encountered a few issues that I wonder if there is a fix for.

 

#1  Lodestar X2C with SLL 3.3 has green stars.  The previous version I used, v2 I think, did not have this issue nor did any of the Lodestar Live versions which is what I ended up using on the night in question. I forgot to record an image showing an example.

#2  Ultrastar-C has yellow-red halo around stars.  This is an ongoing problem that I have seen for a couple versions of SLL now and I think it has been discussed before.  Is there a solution for this issue?  I have attached an example image below.

Thanks,

Jim T.

sample ultrastar-c image with star halos.png

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jimthompson    18

If it helps to see what is going on better, I've attached the same image but split into the three colour channels RGB.  It seems like the RED colour channel saturates sooner than the other two, which results in stars appearing larger in the red channel thus giving them the yellow-red halo.  Is it possible to check each pixel for saturation of RGB values, and if one is saturated and the other two aren't or nearly so then replace the saturated colour value with an average or max of the other two or something?  This might help reduce visibility of hot pixels also which tend to appear as pure red green or blue pixels.

ultrastar-c star halos - colour channels.png

Edited by jimthompson
added idea for solution

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roelb    26

Are you using a filter.

I do have sometimes similar halos with the Infinity (which has same CCD sensor as SX Ultrastar).

Particularly when using a CLS-CCD filter.

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HiloDon    764

Hi Jim,

The green stars are caused by the defective pixel removal tool being enabled.  Sometimes I use the tool and don’t get the green stars, but have yet to figure out what I did.  You can disable the tool and use darks, but some strange artifacts may show up depending on the object.

I think Paul was aware of the other problem you see, but he doesn’t appear to be active here recently.  I hope he’s just busy with summer activities and gets back soon.  I think we all miss his help and support.

Don

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jimthompson    18

Hi Roel,

I was using a filter in the instance when my attached images were captured, however I get the halo with or without a filter.  A year ago when I first brought this problem up I believe Paul said he was aware of it and it had something to do with the debayer algorithm in SLL, but I guess he has not had time to track the issue down.

Regards,

Jim T.

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umasscrew39    4

Hi Don

I have had the defective pixel removal tool enabled but always create a set of darks before I begin.  Should I not be doing both?  I really have not noticed any big issue in doing so but is it best not to do both?

Hi Roel/Jim

I also get the reddish halo around some stars-  the use of filters or not make no difference.  

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HiloDon    764

Bruce,

I would suggest trying both and see if there’s any difference.   Couple of weeks ago I had taken darks and had some issues I thought might be related to them, so I shut them off and just relied on the DPR tool.  It worked so well that I don’t take darks anymore with the Ultrastar C.  Last night though my mono Ultrastar had some amp glow, so I need to take a couple of darks to remove it.  The DPR won’t remove amp glow.

I think I’m not getting the green stars anymore, but I need to run more tests to be sure.  It’s really nice not having to take darks.

The reddish halo is something Paul was aware of and was working on a fix.  Hope he shows up soon.

Don

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