[AstroPy] How does ePSFBuilder work

[Peter Dzwig]

Larry,

On 17/03/2023 16:02, Larry Bradley wrote:
>> Questions: (i) is my understanding correct?; 
> 
> Yes.

Thanks.
> 
  Note that you can’t build an ePSF model from a
> single input star. You need *many* stars (e.g., ~hundred or more) to 
> build a realistic oversampled ePSF model.  Having many empirical stars 
> (which will each have small subpixel shifts) ensures that the 
> oversampled output grid of the ePSF model is well sampled.
> 

OK. Is it applicable in the case of a galaxy cluster?

My problem is that I am looking to estimate the ePSF for a cluster in 
which many of the principal objects suffer (optical)cross-pollution. 
Unfortunately I don't have access to the original (e)PSF and am trying 
to approximate it.

Because of orientations and types of objects in the image I have little 
that could be used in place of a single point object, so I am working 
with a few  "sufficiently isolated" spherical galaxies to generate an 
approximate ePSF.

I'd appreciate any thoughts that you might have,

Peter

-- 

Dr. Peter Dzwig