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lect15 - UCF Physics AST 5765/4762(Advanced Astronomical...

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UCF Physics: AST 5765/4762: (Advanced) Astronomical Data Analysis Fall 2009 Lecture Notes: 15. CCD Corrections 1 Check In: 12:30 — 12:35, 5 min Questions before we start? 2 Summary of CCD Systematics: 12:35 — 12:40, 5 min QE < 100% QE varies I d I d varies pixel to pixel I d varies in time (with temp, etc.) I d has its own noise V bias Read noise Amplifier not perfectly linear Pixels not perfectly linear! Too much charge cancels some bias voltage. Cosmic rays deposit many e - in wells Some pixels have defects (“bad pixels”) 3 Basic CCD Error Correction: 12:40 — 12:45, 5 min Do readout backwards: QE differences were multiplied, so divide them out Dark current was added, so subtract it Bias voltage was added, so subtract it Basic formula: C = R B D F (1) 1
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4 Making the Calibration Frames: 12:45 — 12:55, 10 min This is an art! Sensitive analyses and quirky instruments more robust methods Here are the basic principles Bias frame: average many 0-exposure images, B = 1 N B i Dark frame: D = 1 t tot ( D i B ) = 1 t tot ( D i ) NB
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