Out of focus Star Calculations

adbohn wrote on Jun 25, 2008

I was wondering if it was possible to perform different calculations on stars that were out of focus. The most basic of these tasks would be to find the centroid given the out of focus star's annulus. Other tasks would be to see intensity plots etc. Is this possible?

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Mike Fitzpatrick wrote on Jun 25, 2008

Tasks should still all work, although you might get some funny results. IMEXAMINE for instance has many command to look at radial profiles, contour/surface, a line through the data, etc. STARFIND and some of the photometry tasks will do centroiding, but if the stars are so out of focus as to look like donuts then they might not converge easily.

-Mike

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adbohn wrote on Jun 25, 2008

The images will be distorted in order to obtain a donut shape. I know that sounds like a mean thing to do to an image. I was wondering basically if there were any way to change the input data in order to let it know that the stars will be out of focus (by giving parameters about the size of the annulus or something) in order to find the centroid as accurately as possible. The CCD used will not obtain an elliptical annulus but a circular (or very close to) one, so it should be easier to do.

Thanks for the help, Andy

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Mike Fitzpatrick wrote on Jun 25, 2008

You can certainly do a line plot through a donut, but PSF photometry of it might not work. Try some tasks to see what you get, but in general there is no 'donut_size' parameter to twiddle.

-Mike

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Last post on Jun 25, 2008