Reply To: ZWO ASI 533MM-Pro CMOS Camera for Photometry?

Forums Photometry ZWO ASI 533MM-Pro CMOS Camera for Photometry? Reply To: ZWO ASI 533MM-Pro CMOS Camera for Photometry?

Kevin West

Hello Ian,
I posted this on AAVSO last month ad Arne Henden replied with this. It may be of use in your quest.

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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).


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