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Re: Measuring a huge amount of images

Posted by karenacollins on Jan 23, 2018; 4:34am
URL: http://astroimagej.170.s1.nabble.com/Measuring-a-huge-amount-of-images-tp959p960.html

Hi Petri,

I am working with a team publishing a large number of observations of the same star. I think the best answer for you depends on your telescopes pointing precision, whether the images are plate solved, how stable the atmospheric transparency is, and consistency of focus, seeing, comp star availability, and comp star longterm brightness.

If you have the same set of comp stars available for all observations, and the same aperture size will work reasonably well for all nights, you should be able to run photometry on all images in one run. If the pointing is off from night-to-night, you can plate solve the first image of the night and select "use RA/Dec to place apertures" to ensure the apertures track any large night-to-night jumps.

However, I think you may find that the comp stars may have long term brightness trends that may cause the night-to-night observations to not be directly comparable, unless you normalize each night independently.

If you do the photometry in one run, and then chop the measurements table on night boundaries and copy the header line to each file, you can then load them into AIJ as if they were done separately. Then normalization and detrending of each night could be done separately in AIJ.

If you are willing, the normalization and detrending could be done with custom code in IDL, python, etc., but you'd have to evaluate which would be most time efficient, since I don't the number of different nights of observations. If you have 20 nights of 1000 images, my bet is that the custom coding might not be worth the effort, but if you have 200 nights, of 100 images, then it might be worth considering custom detrend and normalization code.

We had 300 nights of light curves, and still used AIJ to so that we could review the quality of each night of observations before including it our analysis.

Karen