DSS stack wothout darks: 15000 stars registered

[alacant]

Hi

I tried dithering recently and without using dark fames, I'm getting 15000+ stars in DSS. With the darks it registers a more realistic 800 or so: around 20x180s exposures on a Canon 1200D, iso 1600. One of the advantages I thought the dither would bring is to avoid taking darks but the star detection in DSS is taking so long now on my slow E1 laptop, maybe it's not worth it. I understand that each bad pixel is being registered by DSS as a star...

I believe the sigma clip stacking needs the bad pixels so any workaround? Just a quick sanity check would be good at this stage. TIA. 

 

[The Admiral]

I presume that you are adjusting the star detection threshold? 15000+ stars suggests it's seeing noise as stars.

Ian

[Adam J]

34 minutes ago, The Admiral said:

I presume that you are adjusting the star detection threshold? 15000+ stars suggests it's seeing noise as stars.

Ian

Yeah this, and you only see the effect of dithering after stacking. Alter the threshold until you have about 100 stars, that's really all it needs to align the images.

[alacant]

Yeah, thanks. That's gonna cut down the time enormously. I thought the sigma clip thing needed all the points it could lay its hands on.

BTW, I'm DSS stacking just the light and flat frames. No dark or bias. Is that correct?

TIA 

[Xplode]

Try to stack both with and without the dark frames and see if one is better than the other.

If you have enough subs and dithered often enough they should be equal.

[alacant]

19 minutes ago, Xplode said:

stack both with and without the dark frames

...and bias frames? Thanks.

[Xplode]

Use the bias frames

[Adam J]

I dither and use the "remove remaining hotpixels" option seems to work as well as darks for when i dont have the time. Then I just use spot healer to remove the few that get past.

[Waldemar]

since darks do not have anything to do with the optics, only with exposure time and sensor temperature, you can make a library of darks, with the settings you mostly use, or make a master dark. Bias is even simpler, so make a master bias and use it everytime.