2 problems- for now!

[martin_h]

Problem 1 - Any idea what is causing the artifact in the lower half of pic 1? a single sub pushed to show the fault. I thought it was a hair on the lens....but no not that.

Problem 2 - last night I did everything by the book as a test, 30 x 3 min subs then 10 darks, 10 flats, 20 bias, stacked them all and this is what I get - pic 2 - spot the pixels!

[Merlin66]

A couple of comments...

The artifact on the first image looks like a reflection from a bright edge somewhere in the optical train... may be the edge of an adaptor or focusing tube ???

The results of your stack should obviously have been better looking at the sub.

You don't need the Bias frames if your darks are the same exposure as the lights.

What do you get when you stack without the dark removal???

[martin_h]

To be honest they look better with no calibration frames of any sort

[ollypenrice]

I agree about the reflection.

I thnk the problem will lie in the workflow.

How did you do the flats? Maybe the bias has been accidentally doubled. What I would do is make a master flat as a separate item. To do this I would first make a master bias. I would then put the master bias in the stacking software as if it were a dark for the master flat. I'd also hot pixel filter the flats while stacking them.

I don't know your camera so maybe you will need to deBayer the masterflat by shifting it by 0.5 on both axes. (That's what I do with OSC flats anyway). Then I'd Gaussian blur the masterflat to reduce noise.)

I'd also make a master dark.

Then I'd try with flat and dark, flat only, dark only etc. Like Ken I'd ditch the bias at this stage. If you do it this way rather than 'all in one' you may be able to isolate the problem.

Is there any chance that your dark might be upside down?

Good luck.

Olly

[martin_h]

I've tryed using master flats etc still no good. The dark isnt upside down unless DSS turned it.

The calibration files I did last night were done right after the lights - nothing moved, added or removed. the camera is the QHY8. I thought that DSS took care of all the files for you - doesnt it?

[Psychobilly]

It seems to work ok when they are raw files from a DSLR straight out of the camera...

I don't know what "Nebulosity" is doing to the files from the QHY 8 CCD.... if its doing any "processing" on the data at all before saving them...

It might be better if you do all your calibration and stacking in Nebulosity...

Peter...

[martin_h]

Well it looks like a clear night tonight - I'm going to give it one more shot, collect totaly fresh data and give it a bash, if it doesnt work out all the lot will be in a charity shop Monday morning.

[Psychobilly]

Fingers crossed then...

[ollypenrice]

Whoa, it just takes time to sort out the workflow, really. Some simple thing is stopping you from getting the best out of your data. You'll get there.

Olly

[Ant]

When you do the flats do three sets.

Get the ADU count at around 15,000 for the first set, 25,000 for the second set and finally 35,000 for the third set...

I found that the depending on the circumstances different sets of flats work - not sure why...

Got to be worth a go?

Ant