Reject negative fluxes?

[keflavich]

Fitted PSF photometry fluxes can go negative.

Can we include a mechanism to reject them using public methods?

Right now, you can reject them, but it requires modifying a private method. You need this if you're interested in using the residual image or model image. Example:

phot = PSFPhotometry()
result = phot(data)
bad = result['flux_fit'] <= 0
result = result[~bad]
phot._fit_models = [mod for mod, ok in zip(phot._fit_models, ~bad) if ok]

[keflavich]

I'm also not sure that works, since make_model_image uses _fit_model_params, but that doesn't exist for the PSFPhotometry instances I'm playing with.

[keflavich]

with latest photutils, should be:

phot = PSFPhotometry()
result = phot(data)
bad = result['flux_fit'] <= 0
result = result[~bad]
phot._fit_model_params = phot._fit_model_params[~bad]

[keflavich]

Quoting @larrybradley from https://github.com/astropy/photutils/pull/1800#issuecomment-2200314737:

To exclude negative peaks you should bound the flux parameter on the input psf_model, e.g, psf_model.flux.min = 0.