Hello Ian,
I posted this on AAVSO last month ad Arne Henden replied with this. It may be of use in your quest.
Regards
Kevin
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CCD or CMOS
Hi Kevin,
Congratulations for getting back into photometry!
Here are some pros and cons.
CCD pro
usually larger pixels
decent read noise
decent QE
always 16-bit pixels
can be inexpensive if purchased used
CCD con
few new cameras available, so you may have trouble getting service in the future, depending on the vendor
for the same pixel size, higher read noise and dark current than a CMOS camera (though these are really not important for wide band photometry since the sky or star noise will dominate)
new cameras tend to be more expensive for the same sensor area
CMOS pro
lower read noise, lower dark current, higher QE than CCD
can take very short exposures, not limited by shutter speed
lower cost than equivalent CCD sensor size
CMOS con
no mechanical shutter, so darks require covering things and/or blank filter taking up a filter wheel slot
random telegraph noise, which requires multiple images and stacking to fully remove (though low level, and sky/star noise will dominate)
some early generation sensors (such as the IMX183) have amplifier glow
some early generation sensors (such as the IMX183) are 12-bit only
So both sensor types have good points and bad, though most of the “bad” is mitigated by taking exposures through wide-band photometric filters like Johnson/Cousins or Sloan. If I were starting out today, I’d probably select a camera that uses the IMX-571 sensor, such as the QHY268 or the ASI-2600, as this sensor is the best CMOS value right now, and you can use 1.25″ filters with some corner vignetting (or 36mm filters with no vignetting).
Arne
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