Need help with my imaging

[Loki1978]

Hi all,

I just had a couple of questions about my images I'm taking. I keep getting red blue and green dots in the image. Also whats causing the light corners top right bottom left?

My setup is a Williams Optics zenithstar 80, Atik 414 on an skywatcher AZ-eq6

This image just has a couple of stretches in gimp.

 

Edited March 22, 2021 by Loki1978
edited to show image

[Adreneline]

Hi.

The image you uploaded is showing as "Unavailable". It might be better if you upload a jpg so we can see the image without needing to download it first.

I used to have a 414ex osc and it would exhibit similar "light corners" if it was not cooled enough; I seem to recall cooling to -15 degrees.

As for the red, green and blue dots - not sure. What software are you using to pre-process, i.e. calibrate and integrate/stack? Did you take bias, darks and flats? The thought occurs they are 'blown pixels' (full On) and so will show as red, green or blue dots. Darks would remove these during pre-processing.

Adrian

Edited March 22, 2021 by Adreneline
Clarification

[Loki1978]

Adreneline, Thanks for the jpg tip. I've got the post edited to show the image now. I was cooled to -10. When I recently cooled to -20 I was getting ice starting on the sensor chip. I've replaced the desiccant since then. 

I'm using deep sky stacker with appropriate lights, darks, dark flats and biases. Save as a tiff then straight into gimp.

[PeterCPC]

The red blue and green dots are hot pixels. It suggests to me that you did not dither - is that correct?

[Adreneline]

9 hours ago, Loki1978 said:

I'm using deep sky stacker with appropriate lights, darks, dark flats and biases.

Have to say I would have thought the darks would have removed the hot pixels. Can you see the hot pixels on the stretched darks? I would have thought dark frame subtraction in DSS should remove them? (I wrote my reply at about 1.00 a.m. and I was blowed if I could bring the term "hot pixel" to mind - thanks to Peter @PeterCPC for reminding me). Dark frame subtraction should also remove any amp glow.

Looking at your image the corner glows may be light pollution. Have you tried some sort of gradient removal in GIMP?

Looking at your stars it looks as though you are not guiding as there is slight evidence of star trails/elongation- no guiding implies that dithering is not an option.

HTH

Adrian

[rickwayne]

Glows might also be amp glow -- what does a stretched dark look  like  for  your  camera?

[Loki1978]

Hi All, 

Thanks for the replies. I had another play with DSS tonight and I think those coloured dots were my fault mixing up the terms for my darks, lights flats etc. 

Below is the result of a second try in DSS with a couple of quick stretches. 

I still have the light corners and I think I was out of focus (got to 3d print myself a bahtinov mask) I was wondering if some problems could be the security cameras I have in the back garden beaming IR light?

What sort of starting exposure times should I aim for unguided on an equatorial. This was 42 subs at 90 seconds.

Edited March 22, 2021 by Loki1978

[Loki1978]

Also I was a bit confused what sort of debayer I should set in DSS