Squiggles on image

[Scooot]

I took this with my recently acquired star adventurer with my baby tak. Ive stacked it in DSS with 30 bias, no darks or flats I'm afraid. Finished processing it in Photoshop elements. This is my first attempt with the Frac so I'm not too displeased but I've noticed various squiggles throughout the image, some light red and blue. They're very obvious on my pic screen and iPad, not sure how clear they'll come out when I upload. They look as if they might be alignment problems with stacking but I'm not sure so I wonder if anyone can help.

[Steve Ward]

They're "hot pixels" that will disappear when you add dark frames to the stack.

They appear as squiggles because there was a certain amount of drifting , DSS aligned and stacked the stars so the hot pixels (that are in the same position on every frame) appear to move.

[Scooot]

They're "hot pixels" that will disappear when you add dark frames to the stack.

They appear as squiggles because there was a certain amount of drifting , DSS aligned and stacked the stars so the hot pixels (that are in the same position on every frame) appear to move.

Thanks Steve, much appreciated.

[Steve Ward]

You're welcome sir ... 

[Scooot]

There's also a setting in DSS I didn't have ticked in stacking parameters, cosmetic. "Detect and clean remaining hot pixels". I've ticked this and restacked and they've vanished. Also moved the RGB histogram, so other hot pixels are now showing which I suspect would vanish with darks as you say.

[udaiveer]

Truly round stars. (At leas in the middle) ;-)

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[udaiveer]

There's also a setting in DSS I didn't have ticked in stacking parameters, cosmetic. "Detect and clean remaining hot pixels". I've ticked this and restacked and they've vanished. Also moved the RGB histogram, so other hot pixels are now showing which I suspect would vanish with darks as you say.

image.jpeg

Be careful this setting can cause "black holes" in bright stars.

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[glowingturnip]

make sure you use one of the sigma-clipping routines for stacking, not just simple averaging - those routines discard the statistical outliers for each pixel stack and average the remainder so any hot pixel appearing in the same place in just one or two frames will magically disappear, as will satellite trails etc

[Scooot]

After downloading the free trial of pixinsight I've reprocessed this.

I'm pleased with the improvement

[cjdawson]

Yep.

It's worth taking a full set of frames.

Subs - your images

Darks - same exposure as your image, but with no light entering the scope (put the lens cap on)

Dark bias - leave the lens cap on and put your camera to the fastest exposure setting

Flat frame - put a source of light on the end of the scope that produces an even tone across the whole frame, then let the camera work out the exposure time using Apeture priority.

Flat Bias frame - Same as a Dark bias, but images taken with the light source used in the Flat frames.

Take lots of each and it should help to remove all the camera artifacts.