Hi Ashish,
What you're probably looking for is 'rvals' and 'where'. Something like:
$dist = rvals($data,{center=>[$x,$y]});
$flux = $data->where($dist <= 5.5);
$bkgd = $data->where($dist <= 8.5 & $dist >5.5);
cheers,
Derek
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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