Bright yellow stars

[Gavin1234]

Anyone know what might be causing this? These images were all fine last night. Now when I load them into DSS the bright spots come out with this hard yellow. I can’t find any setting in DSS that has changed.

[Stonius (Markus)]

Looks to me like you've clipped out on your red and green channels, but not on the blue channel.

I'm going to take a guess and assume that RGB were all taken at the same exposure times. On my setup, the B channel takes twice as long to reach the same image density as red.

So when you have all channels clipping, you get white in the highlights (R100; G100;B100). When you only have clipping in some channels, the remaining colour is what you end up with. In this case, say you have R96; G88; B08, which is yellow.

Hope that helps

Markus

[Gavin1234]

Thanks but this is on the raw FITS files as soon as I load them into DSS, before I’ve even stacked or touched them. The weird thing is the same files were fine last night. I just checked the same files on another pc and it’s not happening there so it must some sort of DSS setting.

[Stonius (Markus)]

What do the statistics say? Are the FITS files themselves clipped?

[Stonius (Markus)]

Originally Posted by Gavin1234

Thanks but this is on the raw FITS files as soon as I load them into DSS, before I’ve even stacked or touched them. The weird thing is the same files were fine last night. I just checked the same files on another pc and it’s not happening there so it must some sort of DSS setting.

Huh, strange. Well whatever it is, it seems that there is less blue channel present specifically in the highlights, whatever is causing it.

Hope you manage to find a solution. If you do, let us know what it was! :-)

Best

Markus

[Gavin1234]

No not clipped, they haven’t been through any processing yet. The same files look fine in DSS in another computer.

I’ve tried uninstalling DSS and reinstalling but still getting the same problem.

What statistics do you mean? I can’t load a FITS into photoshop, is there another way to look at the statistics for them?

[Gavin1234]

Found it.

The blue in both the RAW and FITS settings was set to 1.200 instead of 1.000. No idea why it did that.

[Stonius (Markus)]

Sorry, I'm on Pixinsight, so I don't know.

Just curious - how do you know for sure they're not clipping if you can't see any statistics? It generally takes some kind of readout to be sure. What levels are you seeing in the yellow highlights?

Are you OSC or mono? What operations have you done on the images so far? If nothing, is it a display issue? Have you played with the screen transfer function (not sure what the equivalent in DSS is).

It's an interesting problem. If you're shooting mono, all I could suggest is stacking the RGB channels again and seeing if the problem goes away.

Good luck!

[Stonius (Markus)]

Originally Posted by Gavin1234

Found it.

The blue in both the RAW and FITS settings was set to 1.200 instead of 1.000. No idea why it did that.

Ah, good to finally get to the bottom of it. Well done. Looking forward to seeing the final result!

Cheers

Markus

[Gavin1234]

Thanks for the help Markus. Very strange that the settings just changed like that.

I’m Collecting a lot of data on these two targets so I’m hopeful of getting a good result eventually. By the morning I should have close to 30 hours at exposures ranging from 10 seconds to 15 minutes

Just a trial version of PixInsight today and I’m really impressed so far. Looks like it’s going to take a while to learn it but eventually I’ll make good use of that data.

[Stonius (Markus)]

I'm still learning pixinsight myself. I find the (free) Light Vortex tutorials very helpful.

Happy Imaging! :-)