Help with 'point up and press'...

[Jonk]

...I aimed my dlsr roughly south, at about 45 degrees and took a series of shots of the sky over a very light polluted Portsmouth.

It was ISO 3200, 18mm f3.5 for 15 seconds, just as a quick test.

After processing, this is what I can get out of the best of the images.

If you look carefully, around the purples and oranges, there are a lot of circles, that I can only describe as like looking through bubble wrap.

The more I try to bring out detail, the more obvious they are.

(Going to extreme to show what I mean)

Am I correct in guessing this is moisture causing this?

[dph1nm]

Dust/dirt on the detector? I would try flat fields.

NigelM

[Jonk]

Hmmm...I wouldn't have thought so...the camera's barely 4 months old and I keep it very clean (cap on) and keep the lenses clean and protected.

It appears too even to be dirt...which is why I was thinking it was moisture?

I was doing some tests, so not really worried about darks and flats etc. at this stage.