Imaging artefact

[almcl]

Just for amusement the other evening I decided to see if I could take images with my Skywatcher ST80 that usually does duty as a guide scope on my SW 200P.

I was not expecting much and was quite surprised at what it achieved, but there are a number of artefacts in the final image which are unlike anything that's appeared before. In the attached heavily cropped image there are 4: 1 red, 2 green and 1 blue, which made me wonder about Bayer matrixes.

Checking the lights revealed a small, five white spot artefact in corresponding places. This doesn't show up on the flats or the bias frames (I don't do darks because of the huge temperature differences that occur, the time they take and because they have never improved matters and often appear to make things worse).

Anyone encountered anything like this? It's not hugely important; once astronomical dark returns in three or so weeks time, I'll be back to galaxies and planetary nebula with the 8" Newt, but it would be interesting to know the cause.

[michael.h.f.wilkinson]

Looks like something from space invaders

[almcl]

Doesn't it just?

That or Galaxians...

[Steve Ward]

Probably hot pixels that appear to 'wander' slightly from sub to sub against the background , basic darks would eliminate them.

[almcl]

Probably hot pixels that appear to 'wander' slightly from sub to sub against the background , basic darks would eliminate them.

But wouldn't these show up on the flats? Or does the shorter exposure of the flat mask them?

[Steve Ward]

Hot ones probably not on short exposures .