gregbradley
23-05-2020, 10:55 AM
I have been using astro CCD cameras now for about 12-14 years. Starting with an SBIG ST2000XM and then getting ripped off about $4,500 on Astromart on an ST10XME that never arrived. To the person's credit they did eventually repay me over several years (I think it took 3 years).
Then an STL11000XCM one shot colour which was lovely but a tad noisy on the dim areas so I got the STL11000m which was a fabulous camera and used by many in making images that are still top shelf by today's standards.
Then the largeKAF16803 cameras like Apogee U16M - a good camera with a ridiculously slow cooldown time (it would take 30 minutes to cool down and if the power supply got interrupted which it would very occasionally (I use a generator at my dark site) it took even longer as it would e slow to warm up (10-15 minutes) and then an additional 30 minutes to cool back down).
I upgraded to a FLI Proline 16803. My mainstay camera for the last 9 years or so. Hard to fault. Its big and heavy though. The large sensor gives a very widefield which creates a great look in images. No FLI Adaptive optics though and no FLI off axis guider either.
Then a FLI Microline 8300. The sensor was perfect, no flaws but I found I did not get very interesting images out of it. I see many excellent images from the QSI683 so QSI would be my choice now for a KAF8300 camera.
I got a Starlight Express 694 Trius which I used for several years. Very sensitive to narrowband and high QE plus low read noise. But I had trouble with non round stars with a bump in them and excessive fuzz around stars which in part was my processing flow but not something I encountered with these other SBIG and FLI cameras. I found out later the bump in the stars was corrected with a firmware update from Starlight Express.
Then a FLI microline 16 (KAF16200) which has been a very good camera overall as well.
I briefly had an SBIG ST8300 which was great for its cost but again the 8300 did not suit my scopes well.
Now recently I got an ASI183mm Pro to see what all the fuss about with these CMOS cameras. After studying the various models for a long time (there are so many models) I chose the 20mp, backside illuminated, 84%QE, 60%+ QE in Ha, low read noise ASI183mm Pro, $1750 at Testar.
First off this camera is tiny and weighs almost nothing. The Trius is small and compact but heavier (still light). Mine cools down 47C below ambient which is almost FLI like performance (50 to 55C). The images are very clean and the sensitivity is very high. Amp glow is there on exposures longer than about 2 minutes but so long as you have accurate darks this callibrates out well. Having gain and offset as 2 additional variables is a bit of a pain. But my FLI cameras have 2 download speeds, the slower one has the lowest read noise and its easy to forget to switch from the faster download speed when focusing to the slower download speed for imaging. Fortunately the download speed is able to specified in the Sky X imaging table.
QE is very high in narrowband and seems similar to the Trius 694 (Sony ICX694 CCD), perhaps even a bit higher. Read noise is about half of the Trius and the FLI ML16 (KAF16200), and nearly a quarter of the 16803.
The small pixels will test your optics, tilt and collimation as its very resolving but its quite a small camera so tilt is less of an issue than it is usually. The sensor seemed to be level as the tilt correction was the same for my other cameras which must be from my adapters.
One interesting aspect of the smaller pixels is that they create rounder stars as there are more pixels in every star. Quite noticeable.
The software supplied with the camera is very good and worked straight out of the box which is great. Most of the other cameras have had their little troubles at various times.
After watching a longish video about the differences of CMOS and CCD and exposure times it does seem shorter exposures are ideal for CMOS more so than CCD where longer exposures seem to rule.
I have been using 300 second gain 53 offset 8 for LRGB and either 300 or 600 seconds gain 111 offset 8 for narrowband and a conservative -10C which the camera achieves very quickly and easily and should all year round.
I could probably go -20 in the cooler months. Despite not getting strong benefits from cooling below a certain point (0 degrees perhaps) if it can cool lower then you may as well take it.
I don't see vertical lines in the sensor like you get in Kodak CCD sensors either. The sensor seems flawless in terms of defects.
Highest dynamic range is at gain 0 which I have yet to try out. Offset - all that does is shift the histogram to the right and prevents black clipping of data.
84% QE and perhaps higher is the most impressive thing about this sensor. It gets the image faster. So low read noise, super high QE, great narrowband sensitivity (over 60% QE for Ha) smallish but decent well depth (15,000 electrons is pretty small). Low cost - if this were a CCD with that performance (none of the usual CCDs have that) it would be many times more expensive. These ZWO cameras cost less than a DSLR.
File sizes are large as its a 20mp sensor and 39mb versus 32mb for the 16803 and similar for the 16200 cameras.
The 6200mm file sizes are 122mb -ouch. CCDstack always moans about not enough memory so its going to be a test.
Binning does not work on CMOS hardware but does have it with software binning. Its not as effective though and it 2X (or is it 4X?) the read noise.
It does improve the SNR though. I have not experimented with 2x2 much so far but don't visually see too much difference.
So overall. CMOS have much lower read noise, the backside illuminated ones (ASI183, 533,2600, 6200 sensors) have 84% QE for mono and still very high in colour. But there are only 3 mono versions - the 1600 (most popular but has microlense reflections), the 183mm (with small pixels)
the 6200 (the most expensive at around AUD$7500). The rest are all one shot colour which have their own advantages and disadvantages.
As far as ZWO versus QHY cameras go I am not in a position to comment but they seem similar. The main comment I read about that is in the past QHY had terrible software driver issues. As I said the ZWO software was the most seamless and easy implementation of any camera maker so far. The Sky X driver was a little hidden on their site but it worked well once found!
The 6200m and the APS one shot colour 2600 have zero amp glow, high QE are 16bit and low read noise but are out of stock everywhere.
Anyway these are my observations so far for those navigating these cameras.
Greg.
Then an STL11000XCM one shot colour which was lovely but a tad noisy on the dim areas so I got the STL11000m which was a fabulous camera and used by many in making images that are still top shelf by today's standards.
Then the largeKAF16803 cameras like Apogee U16M - a good camera with a ridiculously slow cooldown time (it would take 30 minutes to cool down and if the power supply got interrupted which it would very occasionally (I use a generator at my dark site) it took even longer as it would e slow to warm up (10-15 minutes) and then an additional 30 minutes to cool back down).
I upgraded to a FLI Proline 16803. My mainstay camera for the last 9 years or so. Hard to fault. Its big and heavy though. The large sensor gives a very widefield which creates a great look in images. No FLI Adaptive optics though and no FLI off axis guider either.
Then a FLI Microline 8300. The sensor was perfect, no flaws but I found I did not get very interesting images out of it. I see many excellent images from the QSI683 so QSI would be my choice now for a KAF8300 camera.
I got a Starlight Express 694 Trius which I used for several years. Very sensitive to narrowband and high QE plus low read noise. But I had trouble with non round stars with a bump in them and excessive fuzz around stars which in part was my processing flow but not something I encountered with these other SBIG and FLI cameras. I found out later the bump in the stars was corrected with a firmware update from Starlight Express.
Then a FLI microline 16 (KAF16200) which has been a very good camera overall as well.
I briefly had an SBIG ST8300 which was great for its cost but again the 8300 did not suit my scopes well.
Now recently I got an ASI183mm Pro to see what all the fuss about with these CMOS cameras. After studying the various models for a long time (there are so many models) I chose the 20mp, backside illuminated, 84%QE, 60%+ QE in Ha, low read noise ASI183mm Pro, $1750 at Testar.
First off this camera is tiny and weighs almost nothing. The Trius is small and compact but heavier (still light). Mine cools down 47C below ambient which is almost FLI like performance (50 to 55C). The images are very clean and the sensitivity is very high. Amp glow is there on exposures longer than about 2 minutes but so long as you have accurate darks this callibrates out well. Having gain and offset as 2 additional variables is a bit of a pain. But my FLI cameras have 2 download speeds, the slower one has the lowest read noise and its easy to forget to switch from the faster download speed when focusing to the slower download speed for imaging. Fortunately the download speed is able to specified in the Sky X imaging table.
QE is very high in narrowband and seems similar to the Trius 694 (Sony ICX694 CCD), perhaps even a bit higher. Read noise is about half of the Trius and the FLI ML16 (KAF16200), and nearly a quarter of the 16803.
The small pixels will test your optics, tilt and collimation as its very resolving but its quite a small camera so tilt is less of an issue than it is usually. The sensor seemed to be level as the tilt correction was the same for my other cameras which must be from my adapters.
One interesting aspect of the smaller pixels is that they create rounder stars as there are more pixels in every star. Quite noticeable.
The software supplied with the camera is very good and worked straight out of the box which is great. Most of the other cameras have had their little troubles at various times.
After watching a longish video about the differences of CMOS and CCD and exposure times it does seem shorter exposures are ideal for CMOS more so than CCD where longer exposures seem to rule.
I have been using 300 second gain 53 offset 8 for LRGB and either 300 or 600 seconds gain 111 offset 8 for narrowband and a conservative -10C which the camera achieves very quickly and easily and should all year round.
I could probably go -20 in the cooler months. Despite not getting strong benefits from cooling below a certain point (0 degrees perhaps) if it can cool lower then you may as well take it.
I don't see vertical lines in the sensor like you get in Kodak CCD sensors either. The sensor seems flawless in terms of defects.
Highest dynamic range is at gain 0 which I have yet to try out. Offset - all that does is shift the histogram to the right and prevents black clipping of data.
84% QE and perhaps higher is the most impressive thing about this sensor. It gets the image faster. So low read noise, super high QE, great narrowband sensitivity (over 60% QE for Ha) smallish but decent well depth (15,000 electrons is pretty small). Low cost - if this were a CCD with that performance (none of the usual CCDs have that) it would be many times more expensive. These ZWO cameras cost less than a DSLR.
File sizes are large as its a 20mp sensor and 39mb versus 32mb for the 16803 and similar for the 16200 cameras.
The 6200mm file sizes are 122mb -ouch. CCDstack always moans about not enough memory so its going to be a test.
Binning does not work on CMOS hardware but does have it with software binning. Its not as effective though and it 2X (or is it 4X?) the read noise.
It does improve the SNR though. I have not experimented with 2x2 much so far but don't visually see too much difference.
So overall. CMOS have much lower read noise, the backside illuminated ones (ASI183, 533,2600, 6200 sensors) have 84% QE for mono and still very high in colour. But there are only 3 mono versions - the 1600 (most popular but has microlense reflections), the 183mm (with small pixels)
the 6200 (the most expensive at around AUD$7500). The rest are all one shot colour which have their own advantages and disadvantages.
As far as ZWO versus QHY cameras go I am not in a position to comment but they seem similar. The main comment I read about that is in the past QHY had terrible software driver issues. As I said the ZWO software was the most seamless and easy implementation of any camera maker so far. The Sky X driver was a little hidden on their site but it worked well once found!
The 6200m and the APS one shot colour 2600 have zero amp glow, high QE are 16bit and low read noise but are out of stock everywhere.
Anyway these are my observations so far for those navigating these cameras.
Greg.