black marks in subs- any idea what may have caused this?

[aramitsharma]

[Elp]

Is that just one sub? I assume you've applied your flats?

[aramitsharma]

disappeared after two subs. must be internal reflections when my neighbour's arc lights switched on when i went to my garden

[Elp]

How many subs did you stack? I would have thought they would be nearly none noticeable or even rejected at the stacking stage which averages all the data.

[adyj1]

8 hours ago, aramitsharma said:

disappeared after two subs. must be internal reflections when my neighbour's arc lights switched on when i went to my garden

By coincidence I got something very similar last night, when setting up my new 8" F4 Newtonian with a nearby overhead light switched on (small black smudges across each exposure).

I got quite worried until it went away when I switched the light off  #phew

[aramitsharma]

7 hours ago, Elp said:

How many subs did you stack? I would have thought they would be nearly none noticeable or even rejected at the stacking stage which averages all the data.

This was a single sub.. marked it as bad