Help with FITS Selective Trails

[kaymann]

Can anyone help with what is happening here... Bright white stars leaving straight trails. Stuck pixels leaving colored curved trails. 60 darks and 60 flats were used in the stack of 378 30 second lights. The image you are looking at is cropped by 50% to get the size down and zoom in on the trouble spots. The image is aligned and looks decent without these weird artifacts...

Any ideas at all would be helpful and seriously considered.

IC4604_(RHO_OPH_NEBULA),_2026-04-16,_312x30L,_(None),_ZWO_ASI533MC_Pro_average_stacked_duplicate crop.jpg (387.92 KiB) Viewed 493 times

[Gfischer]

I use the 533 for eaa and when my darks get old I can get the hot pixels trailing. I would take fresh darks and make sure you use dithering as well.

[admin]

Hi,

the hot pixel trails are just that - individual hot pixels aren't being corrected by darks/hot pixel removal and they are shifting slowly across the view as the stack progresses and the mount drifts a bit.

For the star trails, my guess is that somewhere in among those frames, one frame had some sort of slippage with the stars trailing in it. That shows up clearly on the very brightest stars and if you look closely you can see a hint of it against the slightly less bright stars. Maybe a clutch slipped or something got knocked at some point. If you have the individual frames then digging through them might find the one with the trailing problem.

cheers,

Robin

[kaymann]

Darks were brand new - same day. I have been using SC for darks and flats. Is it possible that the stuck pixels are intermittent? I say this because the curved trails are dot dot dots not full on streaks. By the way it has been quite a while since I have had a photo without this problem.

I have tried to find the stuck pixels in my darks as well as my lights and cannot find them with blinking...

Just found them while blinking the lights and found some slightly oblong stars on to blinking the darks

Temperatures are consistent throughout all... I blinked the subs and could not find any trailing culprits... I am almost ready to replace the camera but I have a feeling I would only end up the same results.

In Seti Astro Suite Pro I removed several dozen "hot pixel" streaks like above with SAS "Blemish Blaster"

Also when I live stack in SC the darks do not remove the streaks only your hot & cold pixel remover does the job. I have tried ASTAP , SAS Pro for stacking and SC live stack and nothing seams to work so what am I doing wrong with my darks as that seems to be the common thread here...

By the way first good night I will apply dithering.

[kaymann]

Okay I have some answers now:

1) I can see the stuck pixels while blinking the individual darks.
2) The Master Dark does not have the stuck pixels.
3) I can see the stuck pixels in the light subs
4)I did not do good enough job of eliminating the oblong stars while blinking the lights.
a) SAS Pro has a evaluator which cleaned those up so good to go there. One problem solved.

So my master darks are very opaque grey - completely uniform with no variation no matter how far I zoom in with no hot pixels showing.
Aren't the master darks supposed to show hot pixels? so they can be ignored in the master light?

[Gfischer]

If you zoom in you should see the hot pixels in your master dark. I put a link to a 30 sec master dark taken with mt 533 pro. The temp, gain, exposure, offset match my light settings. Hope this helps.

https://drive.google.com/file/d/14evoER ... drive_link

[kaymann]

If you zoom in you should see the hot pixels in your master dark. I put a link to a 30 sec master dark taken with mt 533 pro. The temp, gain, exposure, offset match my light settings. Hope this helps.

https://drive.google.com/file/d/14evoER ... drive_link

That was fantastic.

I can now see that my number of stuck pixels is about the same as yours so I must keep looking at my processing.

Thank you so much for going the extra mile to help me out!

[Gfischer]

It’s great to help someone to pay back for all the help others have given me over the years.

[admin]

Hi,

in answer to your question about intermittent hot pixels - yes, they do happen, and they are annoying...

If they happen in the lights then you get intermittent trails as they turn on/off. If they happen in the darks then you can get a 'warm' average for that pixel in the dark, which then can punch dark holes into the processed image when the hot pixel doesn't appear in the light frame.

For the darks, there is an option in the SharpCap capture dark to ignore outlier pixel values which will try to keep pixel values that are sometimes hot/warm out of the averaged dark. For the lights, use hot/cold pixel removal in addition to the dark to help remove these sorts of pixel problems even when the dark doesn't help.

cheers,

Robin

[kaymann]

Robin, I do have some questions about darks and flats:

Detect and ignore outlier pixel values Check Box...

• is this what you are talking about with transient pixels?

Capture Flat Frame: Create Monochrome Flat Frame

• Should this box should be checked with color 533MC Pro?

Capture Flat Frame: Black level offset correction - None

• When Stacking Darks goes in Dark and Flat goes in Flat - correct?

Capture Flat Frame: Black level offset correction - Capture and Subtract bias frames

• When stacking Dark goes into dark category and do Flats go in flat or dark category?

Capture Flat Frame: Black level offset correction - Capture and subtract dark flat frames

• When stacking Dark goes into dark category and do Flats go in flat or dark category?

I seem to remember you indicating with the 533MC Pro the preference is to do bias flats

The reason I ask is Seti Astro Suite Pro, when stacking allows Darks, Flats and Lights (No folder for bias). It indicates all bias and flat darks go into the dark folder...
I am trying to get this right so my darks properly exclude stuck pixels. My flats are absolutely necessary for HyperStar and darks for stuck pixels.