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  #41  
Old 13-10-2016, 06:05 PM
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Camelopardalis (Dunk)
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But it also means that, say, if said mount could only track well for 30-60 seconds carrying a (R)C8, rather than the 1 hour as seems to be expected, then the owner might get subs out of it that would, after processing, give the owner pleasing results...that has to be a good thing.

Or to be more blunt, (within the margins of diminishing returns) it's no longer a rich man's game
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  #42  
Old 13-10-2016, 06:20 PM
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Originally Posted by Camelopardalis View Post
But it also means that, say, if said mount could only track well for 30-60 seconds carrying a (R)C8, rather than the 1 hour as seems to be expected, then the owner might get subs out of it that would, after processing, give the owner pleasing results...that has to be a good thing.

Or to be more blunt, (within the margins of diminishing returns) it's no longer a rich man's game
That's exactly what I attempted to communicate, but apparently ineffectively.

Hopefully more people will be able to get into this hobby earlier on in their lives, when funds are often quite limited, and that IMO would be the most significant outcome of implementing CMOS in astro-cameras.
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  #43  
Old 13-10-2016, 06:26 PM
Placidus (Mike and Trish)
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Originally Posted by Camelopardalis View Post
But it also means that, say, if said mount could only track well for 30-60 seconds carrying a (R)C8, rather than the 1 hour as seems to be expected, then the owner might get subs out of it that would, after processing, give the owner pleasing results...that has to be a good thing.

Or to be more blunt, (within the margins of diminishing returns) it's no longer a rich man's game
My first astro-camera was a Box Brownie. My mount was half a house-brick. Very steady. A roll of film took eight whopper images. I tried doing really long star trails, and learned about sky glow. Short star trails were better. But when they came back from the chemist, there was no charge, because the laboratory thought they hadn't come out. There was no picture of Snoopy chasing a beach ball. So very economical. My next mount I made myself using a motor from a gramophone, some Meccano pulleys and rubber bands, and a piece of half inch threaded rod for the final drive. The counterweight was a pineapple tin filled with the guts from an old car battery. Probably got lead poisoning.

Mike
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  #44  
Old 13-10-2016, 06:54 PM
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wasn't it mentioned a while back that CCD production was going to really drop off and we were going to be stuck with cmos "in the future"? if they get implemented across the board other astro camera makers will no doubt use the chips and potentially bring pricing down across the board? it would be nice to have access to clean larger sensors at cheaper prices and/or to be able to utilize other top notch solutions other camera makers have implemented.
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  #45  
Old 13-10-2016, 07:44 PM
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I personally don't see CCDs ever dieing, especially for the scientific community. At least not until a CMOS chip with 15 micron pixels, 250,000+ e- well depth and 95%+ QE is made.
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  #46  
Old 13-10-2016, 09:43 PM
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I personally don't see CCDs ever dieing, especially for the scientific community. At least not until a CMOS chip with 15 micron pixels, 250,000+ e- well depth and 95%+ QE is made.
SCMOS is designed to meet the needs of the scientific community and there are some caneras in that market now but they are pretty expensive, like the Andor Zyla, Hamamatsu Orca, and others with QE at min 82% now with ultra low read noise. Interestingly the ASI1600 is on par with the best of the sCMOS cameras in low noise performance.
Not sure extreme well depth is that important for 'relative' short sub imaging, as has been pointed out in posts below this one, ultra low noise, and great QE yes for sure. Just shoot and stack more shallower subs, thus processing capability becomes more important, not to forget storage and raw speed, but these are cheap to acquire.
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  #47  
Old 13-10-2016, 11:21 PM
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SCMOS is designed to meet the needs of the scientific community and there are some caneras in that market now but they are pretty expensive, like the Andor Zyla, Hamamatsu Orca, and others with QE at min 82% now with ultra low read noise. Interestingly the ASI1600 is on par with the best of the sCMOS cameras in low noise performance.
Not sure extreme well depth is that important for 'relative' short sub imaging, as has been pointed out in posts below this one, ultra low noise, and great QE yes for sure. Just shoot and stack more shallower subs, thus processing capability becomes more important, not to forget storage and raw speed, but these are cheap to acquire.
Combining all of the information that has been discussed thus far basically says that for the absolute best SNR is having a low RN camera with large wells coupled with the longest exposures possible on a target. Take the iKon 231, 2.1e- read noise and 350k e- well depth, easy to take 1 hour subs with very low read noise, 10 hours with this camera and you'll have some of the deepest data possible. You can do 10x1h subs and not even come close to saturating on something like the Helix.

10x 1 hour subs at 2.1 e- leaves a 6.6e- RMS where as a 400x90 with the ASI at 1.3 e- has a 26e- RMS.
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  #48  
Old 14-10-2016, 01:05 AM
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Combining all of the information that has been discussed thus far basically says that for the absolute best SNR is having a low RN camera with large wells coupled with the longest exposures possible on a target. Take the iKon 231, 2.1e- read noise and 350k e- well depth, easy to take 1 hour subs with very low read noise, 10 hours with this camera and you'll have some of the deepest data possible. You can do 10x1h subs and not even come close to saturating on something like the Helix.

10x 1 hour subs at 2.1 e- leaves a 6.6e- RMS where as a 400x90 with the ASI at 1.3 e- has a 26e- RMS.
Nice. I shudder to think what that little puppy would set you back...
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  #49  
Old 14-10-2016, 05:14 AM
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Nice. I shudder to think what that little puppy would set you back...
I haven't even been game to do some digging
It is a specialised instrument though, just buying ONE 3nm filter for that is probably out of my price range
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  #50  
Old 14-10-2016, 05:50 AM
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I haven't even been game to do some digging
It is a specialised instrument though, just buying ONE 3nm filter for that is probably out of my price range
But doesn't that point out the obvious issue for all of us? Relative cost of performance, sure 10 x 1 hrs with that camera is going to give you great data, but at what cost? I suggest that some sort of unit cost for performance would help. Is that SNR? And factor in the cost of a mount that can deliver great 1 hour subs.

If low cost CMOS cameras, used in a different way, can get you 80% of the expensive solution, then most likely the market will go in that direction. I would suggest that far more ASI1600s are being sold to amatuer imagers than iKon 231s.

Last edited by glend; 14-10-2016 at 06:01 AM.
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  #51  
Old 14-10-2016, 06:37 AM
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I think you're missing my point a bit Glen, the iKon 231 is a scientific instrument, it is not for the amateur market as such. My point was simply that CCDs are not the way of the past and that CMOS sensors, although great for the amateur community, just are not up to the standards of the scientific community. The SCMOS sensors are a step in the right direction and probably fine for narrow spectroscopy but not for the larger professional astronomical community.

99.99% of the amateur community does not have a large enough imaging circle for the camera. They don't have a focuser capable of carrying what will amount to a near 20kg payload (once a filterwheel/adapters are added). If you have a telescope that can handle the camera then you by definition have a mount capable of doing 1+ hour subs.
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  #52  
Old 14-10-2016, 07:21 AM
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I suppose that the other thing that could be said is that, if you can get the same (or better) result from much shorter subs, there is no need for deep wells.

M&T, the other issue that should be noted is that current CMOS chips have small pixels - they do not match well with long fl scopes, so let's hope that someone eventually brings out a mono CMOS full frame camera with large pixels.
Sony A7s full frame mirrorless camera has something like 10 micron pixels.

Greg
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  #53  
Old 14-10-2016, 07:23 AM
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I think you're missing my point a bit Glen, the iKon 231 is a scientific instrument, it is not for the amateur market as such. My point was simply that CCDs are not the way of the past and that CMOS sensors, although great for the amateur community, just are not up to the standards of the scientific community. The SCMOS sensors are a step in the right direction and probably fine for narrow spectroscopy but not for the larger professional astronomical community.

99.99% of the amateur community does not have a large enough imaging circle for the camera. They don't have a focuser capable of carrying what will amount to a near 20kg payload (once a filterwheel/adapters are added). If you have a telescope that can handle the camera then you by definition have a mount capable of doing 1+ hour subs.
Colin you chose to compare the budget 1600 with the iKon. i did not bring the iKon into the discussion as a comparison or reference to Astro cameras, so yes i am missing a point of their relevance to our use, other than possible flow down effects into our products. My reference to sCMOS cameras was in relation to emerging benchmarks for next gen CMOS for astro use.
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  #54  
Old 14-10-2016, 07:41 AM
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Combining all of the information that has been discussed thus far basically says that for the absolute best SNR is having a low RN camera with large wells coupled with the longest exposures possible on a target. Take the iKon 231, 2.1e- read noise and 350k e- well depth, easy to take 1 hour subs with very low read noise, 10 hours with this camera and you'll have some of the deepest data possible. You can do 10x1h subs and not even come close to saturating on something like the Helix.

10x 1 hour subs at 2.1 e- leaves a 6.6e- RMS where as a 400x90 with the ASI at 1.3 e- has a 26e- RMS.
But I think that you need to consider sky noise Colin - the conclusions from M&T's broadband analysis apply in NB if the read noise is low enough.

at Ha, a fully dark sky produces about 0.5 p/s/m2/arcsec2/nm.
lets make up an appropriate scope for the ikon231 camera - with aperture of 1m2, sampling of 0.1arcsec2, 3nm bandwidth and assume 50% optical efficiency (including QE). if you evaluate the photon flux per pixel using those values, you end up with 0.75 photoelectrons/s/pixel for the sky noise.

Now the camera read noise is 2e. The sky noise will overwhelm the read noise when it is about 3x as large, ie to be dominant, the sky noise needs to be 6e rms. You get that noise from 36 photoelectrons. And at 0.75 photoelectrons/s, you get 36 photoelectrons in less than a minute = you would then be sky-limited on any longer subs.

ie, you would not be able to get any advantage from NB subs longer than about 1 minute with the camera in question on a reasonable telescope. (for interest it would be 20minutes at 10eRN)

An ASI1600 reaches the Ha sky limit with a 10 inch scope and 0.75 arcsec sampling in about 10 minutes at high gain under average dark sky. When it is sky-limited, it will go just as deep as any other sky-limited system (including one based on the ikon231). It just takes less total time on a big scope. Very low read noise CMOS chips really are a game changer and we are just starting to scratch the surface on what they can do - even the ASI1600 is way more than a budget entry-level camera, even though it doesn't cost very much.

ref:https://www.gemini.edu/sciops/telesc...sky-background

Last edited by Shiraz; 14-10-2016 at 04:53 PM.
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  #55  
Old 14-10-2016, 11:48 AM
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I haven't even been game to do some digging
It is a specialised instrument though, just buying ONE 3nm filter for that is probably out of my price range
Couldn't help myself.....circa $US230,000 apparently....ouch!
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  #56  
Old 14-10-2016, 12:52 PM
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Couldn't help myself.....circa $US230,000 apparently....ouch!
I'll have two please...one in red and one in yellow
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  #57  
Old 14-10-2016, 01:36 PM
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I'll have two please...one in red and one in yellow
That would buy 115 x ASI1600MM-Cs assuming that AUD! Imagine that mosaic.
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  #58  
Old 14-10-2016, 01:50 PM
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you can tell I don't have that kind of toy money when my first thought was the power drive at all
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  #59  
Old 14-10-2016, 02:09 PM
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That would buy 115 x ASI1600MM-Cs assuming that AUD! Imagine that mosaic.
Imagine the disk space.
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  #60  
Old 15-10-2016, 08:18 PM
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I can report some favourable results with going from 5 min subs to 10 min @ minimum gain 75 with the ASI, using 3nm OIII FILTERS. Noticeable but not massive difference, but I only compared an individual sub, the difference would be significant when stacked. And this was in bright moonlit conditions, although the target was well away from the moon.
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