HELP!!!!

[martin_h]

What is going on here? - I've over cooked this to show the effect, but what is it and how do I get rid????

[beamish]

Flats , darks & biases ??? Martin did you take any ??

[jgs001]

Dust on the sensor I reckon... flats will deal with that.

[FraserClarke]

Dust on the filter (and maybe CCD sensor window). Looks from the image that you've tried to flat field, but it's gone a bit wrong.

The fact there are some positive and negative images suggest that you're maybe using the wrong flats for one of the bands, or that your flats are out of date?

The 3d effect on some of the dust rings suggests the filter is not returning to the same location after you move it, so the shadow of the dust ring falls at a slightly different place on the sensor (when you divide the data by the flats, you get this +/- 3d effect).

How closely (in time) did you take the flats compared to the data?

[martin_h]

So its dust then? - Thank God for that!

I need some new flat frames and possibaly a clean up of bits and bobs(or the other way round)

Thanks guys I had a bit of a panic on there

[beamish]

or both ??

[martin_h]

LOL Thats the worse part - I did clean everything at the weekend - Its worse now than before I started

[SteveP]

Martin

The dark circles are dust.. and not far from the front of your CCD. The lighter circles are probably from the 'older' flats which you've calibrated with and when you've reassembled everything after giving it a wipeover, haven't lined up in their original position. A new set of flats with your setup in its current position should resolve the issue.

Whenever any part of your imaging train changes, new flats will always be required

Steve