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Jedi2014

M 101 just before summer break

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Excellent, plain and simple.

Btw, just read the information on your website. How did you combine the 15 s and 180 s luminance frames?

Edited by wimvb

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Very nice!  I hope by "Summer break" you do not mean "hiatus from imaging".  

On 27/06/2018 at 13:39, wimvb said:

Excellent, plain and simple.

Btw, just read the information on your website. How did you combine the 15 s and 180 s luminance frames?

Wim--in PI you can integrate subs of different durations together--I have never had a problem with that.  But I did an experiment and integrated 100 1min, 50 2min and 30 or 40 5min together 2 ways.  1) I just integrated them all using one of the 5min subs as the reference.  Came out good. 2) I integrated each duration separately then I integrated the 3 stacks using the 5min stack as the reference.  According to SFS, the second way produced superior results (slightly lower FWHM, less noise and higher SNR.  But the difference was small--I certainly could not see the difference.

Rodd

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3 hours ago, Rodd said:

Very nice!  I hope by "Summer break" you do not mean "hiatus from imaging".  

Wim--in PI you can integrate subs of different durations together--I have never had a problem with that.  But I did an experiment and integrated 100 1min, 50 2min and 30 or 40 5min together 2 ways.  1) I just integrated them all using one of the 5min subs as the reference.  Came out good. 2) I integrated each duration separately then I integrated the 3 stacks using the 5min stack as the reference.  According to SFS, the second way produced superior results (slightly lower FWHM, less noise and higher SNR.  But the difference was small--I certainly could not see the difference.

Rodd

Yes, that would combine the data. The problem with this method is that it should just average all the subframes (or the 3 masters), and you may lose the advantage of having different exposure lengths. I have never tried it, but I would expect the use of HDRComposition in PI to be able to handle this. @MikeODay does something along these lines when he makes his fabulous cluster images.

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8 hours ago, wimvb said:

Yes, that would combine the data. The problem with this method is that it should just average all the subframes (or the 3 masters), and you may lose the advantage of having different exposure lengths. I have never tried it, but I would expect the use of HDRComposition in PI to be able to handle this. @MikeODay does something along these lines when he makes his fabulous cluster images.

True--if you need multiple exposure lengths, such a when imaging M42, or some other high dynamic range target, HDR comp is necessary.  But for targets that don't have a high dynamic range (many diffuse nebula), HDRcomp is not really necessary.  For example, I have 3 exposure lengths for Sh2-119 (pretty dim nebula).  Adding all 3 together is definitely better than any of the individual stacks--much less noise, higher signal, etc. As long as the reference image is chosen carefully-I don't see a problem.

Rodd

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Like Rodd wrote, I used method 2. The result was better than every single stack. The 15s exposures where only a test because of the new camera. As I did not see any advantage, I will not do it again. 

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