lect14 - UCF Physics AST 5765/4762(Advanced Astronomical...

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Unformatted text preview: UCF Physics: AST 5765/4762: (Advanced) Astronomical Data Analysis Fall 2008 Lecture Notes: 14. Bad Pixels 1 Check in: 2:00 — 2:10, 10 min • Questions before we start? • Collect HW6 • How much time spent in each HW? • How is HW7 • http://stsdas.stsci.edu/numarray/numarray-1.5.html/ • debugging and “theoretical programming” • Missing plots from last time. 2 Apphot Demo: 2:10 — 2:20, 10 min 3 Optimal Photometry: 2:20 — 2:35, 15 min • We could do better: – Don’t count as far out for dim stars, just count part of flux and adjust for known under- count (like census doesn’t) – Or, do weighted sum, giving less weight to distant pixels – Fit a sloping background better – Don’t use interpolated values from bad pixels • Theory: F * , tot = F * , pix p G ( x, y | σ x , σ y , x , y ) (1) • Compute this, and use optimal weighting for an average to many σ distance from x , y • Optimal weighting: σ 2 * , tot = σ 2 * , pix p G ( x, y | σ x , σ y , x , y ) 2 (2) • Must also add σ sky , σ readnoise , etc. in quadrature to get σ pix • Now, find mean with these error estimates 1 • If star noise dominates (bright star), this is like aperture photometry...
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This note was uploaded on 11/09/2009 for the course AST 4762 taught by Professor Harrington during the Fall '09 term at University of Central Florida.

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lect14 - UCF Physics AST 5765/4762(Advanced Astronomical...

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