Quote:
Originally Posted by bluesilver
Sorry to bother you again with yet more questions,
Got everything back up and running again, just got to test it all out when we get clear skies.
I have ben working on the Flats Aid in APT, It appears that adjusting the light level, ( in my case it is a dimmable light box ) it is like a fine tuning of the histogram, while changing the ADU vales is a more course adjustment, at least that is what i am finding.
Si i have sort of ended up with an ADU value of 22000 for the asi2600mc,
This puts the 3rd peak of the histogram about half way along.
I the images below, the first one is with an ADU vale of 22000 and the range comes back at 12338 - 31587, i think this is look ok.
The second image is with an ADU of 30000 and the range is 16494 - 41419 and the 3rd peak is a little over half way along, but i think this is way over exposed.
I use the astronomy.tools to work out the arc seconds per pixel which comes back very simular to what you have said, 0.73 or 0.74 using astronomy.tools site
I do get wildly different histogram results depending on what you select on the histogram, ,like Log, Auto St-L, Auto Str-R, Local ( the range results remain results unaffected of course)
So just interested to know if i am on the right track here, to me it looks good, but still learning about this.
Cheers,
Peter.
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Peter,
Yes you are on the right track !!!!
I’m using APT v3.90 whereas your using v4.10 which has a few more features like showing the Gain value in Flats Aid but generally both do the same thing
Yes your key to good Flats is your “ADU range on the Histogram” with Local button , you just have to juggle the ADU target value and the brightness of your light source to achieve the best range ( definitely a Range no higher than 35,000 or halfway. 31,000 to 33,000 max on your ADU histogram Range is excellent)
The ADU range of 12,100 to 31,000 approx and your Histogram looks OK to me
Another thing to check is on the left side of the Histogram you just want to make sure your not black clipping but your 1st peak or left hand peak is around 12,100 which is fine , my 1st peak or left hand peak is usually around 8,500 to 9,000 which is also ok
Do you use a white T shirt stretched over the end of the scope ? I find a nice white T shirt works well, it gives you some flexibility with your light source and ADU Range.
I usually take 40 Flats and 60 Bias
A lot of folk say just take 15 to 20 Flats and 20 Bias but I still had some Vignetting with small amounts of calibration frames
To me the more the better as the calibration will result in less noise due to the Stacking algorithms
I revised the DSS settings again checklist for Stacking and using Startools, so here it is ( only minor changes and an addition)
DSS Latest Settings for both RGB and Narrowband data ( Prerequisites for Startools )
1/ Tick “No White Balanced Processing” in Raw Files Digital Development
2/ Leave “Set the Blackpoint to 0” unticked in Bayer Matrix Transformation
3/ Select “Per Channel Background Calibration” in Stacking Parameters even though when using Startools it should be “No Calibration”. I found Per Channel Calibration no issue when using Startools.
4/ In Stacking Parameters, Lights , Channel Background, under “Options” select Linear and None
5/ Select either “Standard Mode”or “Intersection Mode” in Stacking Parameters (Intersection helps reduce stacking artefacts)
6/ Tick “Align RGB Channels in final image” in Stacking Parameters
7/ Digital Development Process Fits setting and Raw settings select Bilinear Interpolation
8/ In Digital Development Process Settings ensure you tick “Monochrome 16bit Fits files created by a DSLR or a colour CCD camera” when using a DSLR or OSC camera.
9/ Stacking Parameters, Lights use Kappa Sigma Clipping
10/ Stacking Parameters, Flats use Median Kappa Sigma Clipping
11/ Stacking Parameters, Bias use Median Kappa Sigma Clipping
12/ In Stacking Parameters under relevant Tabs , only tick box at bottom that reads “Use all available processors”
13/ Ensure you save your stacked file as a “32 bit channel integer Fits files with no adjustments applied”
No problem if you any further questions or queries
I’m still learning as well after 5 years at it , you never stop learning in this hobby
Cheers
Martin