IRAF mask images with sigma clipping

[Firestar-Reimu]

I have a school homework which MUST use the #$%^&* IRAF

First I have to produce a median background from this image

but before fmedian image x y I need to mask out all the stars

I am going to do this from a sigma clipping, for example mask out all pixels with sigma>3

In photutils I can do:

sigma_clip = SigmaClip(sigma=3.0, maxiters=10)
threshold = detect_threshold(data, nsigma=2.0, sigma_clip=sigma_clip)
segment_img = detect_sources(data, threshold, npixels=10)
footprint = circular_footprint(radius=10)
mask = segment_img.make_source_mask(footprint=footprint)
mean, median, std = sigma_clipped_stats(data, sigma=3.0, mask=mask)

But I cannot find any tasks in IRAF which can do sigma-clipping

How to mask images with sigma clipping in IRAF?

[olebole]

The trick may be to use the "search" function of the documentation. Or to call a Python script from IRAF.

[Firestar-Reimu]

I have searched the documentation for hundreds of times ... (sad)

[Firestar-Reimu]

I tried objmask and produced a Perl file mask.pl, but I find that when I use fmedian, it cannot just ignore the masked pixels, instead it treat them as pixels with very large/small values.