Monday, June 17, 2013

1306.3273 (S. M. Pokhvala et al.)

Performance of commercial CMOS cameras for high-speed multicolor photometry    [PDF]

S. M. Pokhvala, B. E. Zhilyaev, V. M. Reshetnyk
We present some results of testing of commercial color CMOS cameras for astronomical applications. CMOS sensors allow to perform photometry in three filters simultaneously that gives a great advantage compared with monochrome CCD detectors. The Bayer BGR colour system realized in CMOS sensors is close to the Johnson BVR system. We demonstrate transformation from the Bayer color system to the Johnson one. Our photometric measurements with color CMOS cameras coupled to small telescopes (11 - 30 inch) reveal that in video mode stars up to V $\sim$ 9 can be shot at 24 frames per second. Using a high-speed CMOS camera with short exposure times (10 - 20 ms) we can perform an imaging mode called "lucky imaging". We can pick out high quality frames and combine them into a single image using "shift-and-add" technique. This allows us obtain an image with much higher resolution than would be possible shooting a single image with long exposure. For image selection we use the Strehl-selection method. We demonstrates advantage of the lucky imaging technique in comparison with long exposure shooting. The FWHM of the blurred image caused by atmosphere turbulence can be decreased twice and more.
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