Subpixel Sensitivity
Originally uploaded by Astro Guy.
I spent most of the day work on better routines to handle partial pixels in aperture photometry. Usually, a simple approximation is used to calculate the contribution of pixels at the aperture boundary. These approximations can add systematic errors to extracted photometry. So I decided to actually integrate each pixel with exact formulae. This ended up being a logic brain bomb. Lots of if statements, but in the end it works. Time to test it out. I also want to include a bilinear pixel interpolation scheme to take into account the slope of the PSF when using small radii. I'll attack that tomorrow.
Now some real issues when dealing with CCD images. The figure shows the dependance of the measured instrumental magntitude as a function of the PSF centroid. There is a clear dependance. Since the PSF is unsampled (FWHM < 2 pixels) the CCD filling factors come into play and have to be corrected for. That'll be an exercise for next week.
3 comments:
Hey Jason,
Can I link to your site??? I don't understand much of what you are talking about, but its cool to know a real astonamist.
drop me a line sometime and I'd love to see your pictures of the drive to Calgary. Nice part of the world.
Jennith
Go ahead and add the link. I'll add yours on this end as well!
You can check out my pictures on flickr:
My Photos
And goto to the Calgary->Vancouver set.
Thanks for adding me, you too are now added. :D
Blogging is addictive. I had hoped to write something worthwhile to keep my writing skills sharp, but really on a good day I write a caption and that is about it.
Hope you are well, let me know when you are in town
Jenn
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