It would be very useful for astronomers to have a scale bar showing angular scales such as degree (°), arcmin (') and arcsec ('').

For example, this can be done by adding the so-called pixel scale in the units of arc seconds per pixel (or even more available units) as an input. For example pixel scale = 0.2 implies that each pixel spans 0.2 arcsec. Here is the best I could do with the current version of matplotlib-scalebar.