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Old 27-10-2013, 08:05 PM
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RickS (Rick)
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Originally Posted by gregbradley View Post
Speaking of that, what rejection parameters have you found workable? I tend to only use hot and cold pixel rejection and have noticed that helps. I have not noticed the other rejections to help at all unless I am simply using the wrong settings.

Greg.
Greg,

I use CosmeticCorrection for the hot and cold pixels and then I experiment with a couple of different rejection algorithms depending on how many subs I have. For a handful of subs, Percentile Clipping usually produces the best results. A few more and you're in Sigma Clipping country. When you get up to 10 or so that's Winsorized Sigma Clipping and then 15+ is usually good for Linear Fit Clipping. ImageIntegration spits out some SNR data so you can compare how well each algorithm works. I start with an integration with no rejection which will give me an upper limit for the SNR. Then I play with the algorithms and parameters to see how close I can get to that SNR and still get rid of any satellite trails, cosmic rays, etc. It can be a slow process but will result in a close to optimal SNR.

Cheers,
Rick.
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  #22  
Old 28-10-2013, 11:30 AM
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Originally Posted by Bassnut View Post
Using OPT as a reference. A FLI proline 11002 is about $500 more than an STXL 11002, and An FLI micro 6303 is about $400 more than a STXL 6303. It doesnt appear that FLI make a proline 6303 anymore. SBIG dont do a 16803 in STXL. Interesting aside, FLI seem to be pushing electronic shutters, mechanical is an option on most models these days. I dont know what the implications are, interesting.

Im not knocking FLI, itelescope loves em, excellent reliability and support apparently, but they are more expensive than SBIG and as you say not flash in the self guide/AO department, if thats of interest.
Yes these STXL cameras look appealling. 16803 is only STX for some reason. Probably because the carousel of the filter wheel won't take 50mm square? Or perhaps they don't want to cannibalise STX sales?
I am sure you can get any chip in any FLI camera. Its probably just a listing thing on OPT's site. Electronic shutters are only KAI series chips aren't they?

FLI are definitely good and they were way ahead there a few years ago. Its seems on the surface the competition caught up. They have the edge on Apogee still as Apogee insists on the slow cooldown and warm up before cool down again if the cooling is interrupted (like a brief problem with power). Apogee is slightly thinner so a bit less backfoucs required. QSI don't have their 700 series out yet so really the only competition still is from SBIG who seem to be doing very well.

Greg.


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Originally Posted by RickS View Post
Greg,

I use CosmeticCorrection for the hot and cold pixels and then I experiment with a couple of different rejection algorithms depending on how many subs I have. For a handful of subs, Percentile Clipping usually produces the best results. A few more and you're in Sigma Clipping country. When you get up to 10 or so that's Winsorized Sigma Clipping and then 15+ is usually good for Linear Fit Clipping. ImageIntegration spits out some SNR data so you can compare how well each algorithm works. I start with an integration with no rejection which will give me an upper limit for the SNR. Then I play with the algorithms and parameters to see how close I can get to that SNR and still get rid of any satellite trails, cosmic rays, etc. It can be a slow process but will result in a close to optimal SNR.

Cheers,
Rick.
Thanks for that Rick. I'll have to check that out. I find my Proline downloads are very clean so perhaps that is one reason I don't see a gain apart from hot/cold pixel which seems to get rid of the little black specs that seem to show up if you don't.

Greg.
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