Not exactly sure what the 'flux' here refers to but what you describe
sounds like a convolution with a binary circular mask (astronomers
please correct me). PDL has various (fast) convolution functions.
Christian
On 19/03/2008, at 10:50 AM, Ashish Mahabal wrote:
Hi,
How does one put a circular aperture on an image in order to
measure flux
within it?
For instance, if in a 2048x2048 fits image I wanted to use a circular
aperture of size 11 pixels (diameter) and sum the counts, what is
the best
way to go?
How do I collect the "background" by using a larger aperture (say
17) and
excluding the earlier aperture (i.e. an annulus)?
Cheers,
-ashish
Ashish Mahabal, Caltech Astronomy, Pasadena, CA 91125
http://www.astro.caltech.edu/~aam aam at astro.caltech.edu
Do not try to bend the spoon. That's impossible.
Instead, only try to realize the truth.
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Christian Soeller PhD Dept. of Physiology +64 9 3737599 x82770
University of Auckland Auckland, New Zealand fax +64 9 3737499
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