Question, problems, about Christmas tree

[Fay]

I did 25x300 of Christmas Tree, is the Rosette near, as in the bottom right corner I have a donut shaped occurance, which, if it was Rosette, I would have thought it would have come out more pronounced.



Also, whe stacking with my flats, the image is black & I cannot get anything out of it, so thinking I have a flats problem

Also, down the left side of the stacked image, I have a black line, about 1/2" in  &  a 1/4 inch black rectangle at the top. On the Right side, there is a black rectangle bottom right.

I did restack a couple of times, Mark, but it is still there & I had to crop the sides. All these problems I have never had before.

[Fay]

I have done a few tests on desktop, results:

If I stack 25x300 Lum in DSS, I get the line & black rectangles

If I stack 25x300 plus flats & flat darks, it only uses 1x300 Lum. Hence why I cannot get anything out of it.

[mickw]

Have you got a Flat marked as a Dark ?

Sounds like DSS is seeing a particularly bright frame and averaging out the rest accordingly.

Sort of sounds logical 

[Fay]

Well, this is a 3x300 stack from Stairs Farm
Things in common= dedicated 0.8 FR/ ED80 & clip in filter

[MarkS]

It is clear that rotation has taken place over the course of the imaging session - DSS will tell you how much it had to de-rotate each frame to align the stars. 

This happens when polar alignment is slightly off - the subs will rotate around the guide star.

Mark

[Fay]

Mark I stacked again & info for each sub was:

1/  0 8 0 1      angle 0 0

2/  65 3 56 7          0.5

3/  0 0 0 0              0.0

are these the figures you mean?
Also , would this be the answer to the prog only stacking 1x300 when using the flats?

Thanks Mark

[Carole]

Hi Fay,

I got something similar to this when I did stacking in DSS when I was doing unguided imaging (only mine was a lot worse than that with black steps and several lines as the frames rotated).  I agree with Mark that the box and line is where a frame has shifted. 

No idea why it only stacked one luminance frame, but that also happened to me once in DSS, I never got to the bottom of that. 

Carole

[The Thing]

Hi Fay, I have have the same doughnut in the corner of my frames. Thought it must be amp glow.

[Fay]

Duncan, I thought you had a donut as well!

[MarkS]

Yes,Fay.  Those are the figures I mean.

Dunno why it only stacks one frame when using darks/flats.  Is there a "quality threshhold" parameter somewhere, I wonder?

Doughnut at bottom right of a 350D frame is amp glow.  Here's an example: http://www.markshelley.co.uk/Astronomy/Projects/mkiiframeafter.jpg

To combat this, you should take darks immediately after imaging - while the CCD is still warm.

Mark

[Fay]

I have got 100% ticked for quality, did not do darks just flats/ flat darks

[The Thing]

Hi Fay, I would use 80-90% in the quality box so DSS uses only the best lights.

[Fay]

Ok, I know why only one light frame was being stacked when using flats & flat darks.......i was selecting the flats & dark flats in the wrong order................

[MarkS]

Glad there was a simple explanation. 

I've never taken a flat dark in my life.  I would guess that they're only required if you are using a dim light source (hence long exposure) for your flats.