Old 03-03-2011, 03:19 PM   #11
dayers88
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Do they give any information on how the various rejections work? The CCDStack "manual" on their website drives me batty. It usually doesn't tell me what I'm looking for. I'm obviously looking in the wrong place.

I'm not losing any sleep over it, but it bugs me!

Dave
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Old 03-03-2012, 04:52 PM   #12
Jrobin
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Noob question: Would it be better to collect the subs across separate nights and combine or take them all in one go at the same time? Where does most of the noise come from? If its atmospheric wouldnt it make sense to have a data set from varying atmospherics so that the software can do its thing? Afterall, 11 identical images, with the same noise, isnt going to be useful? Question is then, where does the noise come from? It must be transient effects, like clouds, cosmic rays, satellites, moon glow. The noise in the camera is going to be consistent. So, im guessing taking say, 5 lots of Ha, S,O across 5 days is better than 3 lots of 5Ha one night and 5S another night and 5O on the third night. Of course, doing it the first way round is inefficient use of the equipment; bet then efficiency and quality are always somehow traded. Any thoughts?

Last edited by Jrobin; 03-03-2012 at 07:34 PM.
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Old 03-04-2012, 03:21 PM   #13
dayers88
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Hi Jrobin,

Good questions. Noise, by definition, is never identical, so it doesn't make any difference when the frame was exposed. (If I'm wrong about this, we will no doubt hear from someone!) My data-bank for a given object is necessarily obtained whenever I have the opportunity, and after calibration I just toss it all into the same batch for registration and integration.

Dave
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Old 03-04-2012, 06:21 PM   #14
Jrobin
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Thats what i think im asking. If we have two data sets, we can find common data points and the rest is noise. But wait! The first set could comprise all of noise and coincident data is merely a result of chance. Hence, the more sub frames, the high confidence we can have in common data points. I guess then, all being equal, the noise from night to night might be more variable than the noise taken 20 seconds later, yet its still noise. [for instance changes in cloud, humidity, wind, moon shine] Mmm... In which case i might re-program the schedule to make efficient use of telescope time rather than have it switch filters and re-calibrate between images.
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Old 03-05-2012, 07:16 AM   #15
dayers88
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Thinking about this makes my head hurt! I think you are on the right track. Scope time costs, and each imaging session should be scheduled to minimize the overhead from filter switching, etc., IMO. Noodling such stuff is what makes astroimaging so challenging . . . and fun. The bottom line is a pleasing image that takes full advantage of the existing data.

Dave
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Old 03-05-2012, 10:27 AM   #16
Jrobin
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yeah, yeah! Ive been thinking. Its quite head noodlin! What is noise? IS there such a thing as more noise, or merely different noise? I can really see the appeal of all this; its almost critical path analysis and n-th degree optimisation. So, going for 3x [O], 3x[S], 3x[Ha] to start with. Then theres the art to blending the plates. All good. To have a practice, i might get out the old DSLR and do a series of night shots to see how the stack software works. By the way, is there anywhere on here that highlights the difference between the scopes? Could the plates from LB001 be used with LB002 in terms of useful stacking?
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Old 03-06-2012, 07:25 AM   #17
dayers88
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If you really want to understand the fine points of imaging, find a copy of The Handbook of Astonomical Image Processing, by Richard Berry and James Burnell. This is recognized by many astroimagers as the "bible" on the subject. It deals in painful detail with the kind of questions you (and I) ask.

As for the difference between the scopes, just click on Use Telescopes and check out the specs for each one (the little arrows at the bottom of the scope image).

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