artifacts around bright stars

[esheldon]

I'm seeing artifacts around bright stars. I've attached an image showing an example. You can see what might be FFT artifacts as vertical/horizontal features. there are no detector effects here.

I can provide an instcat and yaml file if needed

[cwwalter]

Well... that looks like the airy rings with the modulation on top of it..

Is is a saturated object? Is so, see this discussion about how we assume in this case it is monochromatic so they don't get washed out.

https://lsstc.slack.com/archives/CHXKSF3HC/p1695182534709269?thread_ts=1695175590.496979&cid=CHXKSF3HC

I don't know if I have seen then just in a line like that though.

[jmeyers314]

Hmm.. I think if this were Airy the rings would circle all the way around. FFT artifact feels right to me.

[rmjarvis]

Yeah, that's the kind of FFT artifact that typically happens in bright stars. You need pretty huge FFTs to avoid them (via smaller than normal folding_threshold and maxk_threshold).

[esheldon]

[esheldon]

Example in the amplifier image with detector effects

[esheldon]

Here is a tar ball with config file, instcat, and a script showing how to run it

https://www.cosmo.bnl.gov/www/esheldon/data/lsst/test-artifacts.tar