Where did I go wrong?

[Datalord]

I had a session on the Pleiades yesterday and got something I'm less satisfied with.

Tech: Celestron evo 6, field reducer, Sony a3000, iso800, 90*30s, about 20 dark, flat and bias frames.

This is what I got from DSS: (https://www.dropbox.com/s/m0ckrpjn2jfm753/Pleiades Stack.TIF?dl=0 )

Now, I attached the stacked output from DSS and my feeble attempts in StarTools. But something went wrong in the capture, I think, because that noise on the edges is just ugly. But what? Where did I go wrong?

[ollypenrice]

There's a lot of vignetting despite the flats. The flattener-reducer has a speciified chip distance (they all do) so firstly do you have that distance correct? You may need to look it up for your particular flattener.

The arc-like artefacts from the stars may be internal reflections, which can be the bane of focal reducers, especially on very bright stellar targets. Firstly, though, check that chip distance.

Olly

[Datalord]

Checked the distance and measured it on my kit. Should be 105mm and that is exactly what it is when the camera is fit. Maybe I should just not add another item in the chain before I have it sorted without the reducer.