Quote:
Originally Posted by glend
Consider the quantum efficency of the sensors, the ASI 120MC (75% QE), and the 290 mini ( 80%+), have very high QE numbers compared to the others, and gain is not that important imho. Note the mini detects far more stars than the 120MC, even at the low gain setting. The clear winner is the 290 mini.
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Absolutely. Increasing the gain did not seem to improve things much with the 290 mini or 120MC. I still have to confirm but I have a feeling that with the 290 mini the stars in PHD2 got brighter and bigger with the higher gain and hence saturated, i.e. unusable for guiding.
Also, one of the reasons I said the comparison was not fair is that 290 mini has a mono sensor while the other ones have a Bayer filter which will reduce the efficiency. A better comparison would have been ASI120MM vs 290MM mini and the mono mods of the SPC900NC.
Another interesting thing was how much the good old SPC900NC improved with the long exposure mod. Without it the exposure is limited to about 60ms and the software has to add images to achieve longer exposures. Of course the read noise gets added as well and the effect of this is quite significant, as shown in the top two images.
I forgot to mention, those were all 2 second exposures.