PSF stamp size large

[laldoroty]

In phrosty.imagesubtraction.get_imsim_psf():

psf = config.getPSF_Image(501, x=pxradec[0], y=pxradec[1]).array.T 

This says that the stamp size of the retrieved PSF from roman_imsim.utils will be 501 x 501 px.

Dan says Roman project won't know the PSF beyond ~30x30. So:

1. Why so large? (ask Lei)
2. Can we make it smaller?

[laldoroty]

Lei says "it is a little bit abitary. but since space telescope psf usually has a long tail/spikes. we want to preserve the whole structure. so the size should be large enough. also, we found any discontinuity in psf kernel can result in some undesired features to diff. The problem is the truncation at the kernel boundary. if you can make sure there is no significant truncation after you reduce the size, that's fine I think"