![]() If you can test yours and post them (dark current comparison and final noise level in ATIK and 174MM cooled) please do it for me to know IF my camera is faulty of if the 174MM noise is really BIG. To the point that I think is not really usable for dim objects. In terms of noise It is light years away from an ST8, from an atik is megaparsecs away. What I am saying is that the dark current is VERY HIGH compared even with very old CCDs and the final noise is very high as a consequence, drowning details and dimmer stars. I do not care about read noise(it is similar to atik) as exposures are much longer and being dominated by dark current noise. Ill recheck now if I had some issue with my measurements. Ive read your article, very nice indeed, but it focus the usage of the camera more on very bright objects. There is something odd here when you say that is similar to atik314. The difference is enormous to the point that I am thinking to buy an ATIK as the price difference is not big considering the difference in performance.īefore buying Ive searched all specs, datasheets etc to look for dark current level in 174MM cmos but found it nowhere. To the point that a friend with a 14 inches telescope can see in details things that I cannot have a hint with a 20 inches scope. Ĭompare dark signal fro ZWO and from the CCDS, mainly ATIK 314. Press GO and that is it.Īnd here data from some new and old CCDs. Set working folder in settings and write the name of files you got without extension. ![]() Go to the "Misc" tab and get two bias, two darks and two flats. Please use this software or any other and do your own measures to see if this is true OR my CCD is defective in some way. My conclusion is that there are three possible explanations :ġ - The temperature it shows is not the CCD but from another place and the CCD is at a much higher temperatureĢ - The CMOS chip has a VERY HIGH dark current killing longer exposuresģ - My camera is faulty (what I do not believe because Ive got a 178 cooled and it has the same behavior) Notice also that SBIG is at much warmer -10C than ZWO -20C and this means that the difference is much worse than Ive pointed, if at same temperature. In SBIG it is small as dark current is much less. Take a look below and see the difference in offset(bias) mean level and dark mean level. Regarding ampglow yes, it is there, it is big, but does not affect the area that I work with in spectroscopy. ![]() The consequence for normal deepsky imaging is obvious. In fact this makes ASI174MM useless for dim signals even if with bright stars it works OK in spectroscopy. Dark noise is 7 to 10 times worse than in a old ST8. I've selected the darkest area, well away from the ampglow. I use ISIS to measure and then yesterday I have decided to measure some my CCDs to compare. My expectation was that at the target price it could be a competitor to ATIK314, but it seems light years away. I am using for spectroscopy and results have been nice except that when I go fainter the noise dominates wildly. Let me know if my reasoning is faulty in some way. In short, it seems that it is a LONG way from a cooled CCD even if we are talking of very OLD brands. Then the better QE does not payoff either. With ZWO 174MM the total noise it s 10 times higher than an ST8 with a 900 seconds exposure. I have an ST8 and the dark never accumulates much even with very long exposures. This means that for exposure longer than 30 seconds the fact that is cooled does not really make a difference in total noise when comparing to a CCD. An SBIG ST8 with -10C has a 0.045 electrons per second and it is considered a very NOISY CCD. In the order of 0.47 electrons per second with a -20C temperature. In testing the cooled 174MM I had observed a really BAD dark current. ![]()
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