problem with apflatten

thsyu wrote on Mar 10, 2015

Hi!

I'm attempting to normalize my ESI flats (10 orders) with apflatten, using a trace as defined by a bright hot rotator star. We fit a high order polynomial to the extracted flat field spectrum, and my problem is that my resultant normalized flat is normalized to 1 for every order, except for the edges of each aperture, which appear to have noise of ~5-10%.

I've tried adjusting the threshold parameter over a wide range of threshold values: a threshold of 20000 yields a normalized flat of 1 everywhere, and a threshold of 0.1 through 10 has the central part of each order with a value of 1.

Does anyone have any clue on what's going on here? Thanks!

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Last post on Mar 10, 2015