Research on performances of back-illuminated scientific CMOS for astronomical observations

摘要

To evaluate performances of a back-illuminated scientific CMOS(sCMOS)camera for astronomical observations,comparison tests between Andor Marana s CMOS and Andor iKon-L 936 CCD cameras were conducted in a laboratory and on a telescope.The laboratory tests showed that the readout noise of the sCMOS camera is about half lower,the dark current is about 17 times higher,the dynamic range is lower in the 12-bit setting and higher in the 16-bit setting,and the linearity and bias stability are comparable relative to those of the CCD camera.In field tests,we observed the open cluster M67 with the sCMOS and CCD cameras on a 60 cm telescope.Unlike the CCD camera,the sCMOS camera has a dual-amplifier architecture.Since a 16-bit image of the sCMOS camera is composed of two 12-bit images sampled with 12-bit high gain and low gain amplifiers simultaneously,it is not real 16-bit output data.The evaluation tests indicated that the dual-amplifier architecture of the s CMOS camera leads to a decline of photometric stability by about six times around specific pixel counts.For photometry of bright objects with similar magnitudes that require high frame rates,the s CMOS camera under 12-bit setting is a good choice.Therefore,the sCMOS camera is fitted with survey observations of variable objects requiring short exposure times,mostly less than 1 s,and high frame rates.It also satisfies the requirements for an offset guiding instrument owing to its high sensitivity,high temporal resolution and high stability.