Why do astronomers never put a scale on their photographs? I have been looking at images of the Bird nebula, a collision of three galaxies, but in none of the dozen or so that I have found, nor in the accompanying text, is there any scale to show how much (or how little) sky this represents. No cartographer would omit a scale of distance from, say, an isolated Pacific island, but very very seldom do I see an arc-second, or whatever is appropriate, scale on a photograph of the sky. This omission is not just for this one image, amazingly it is true for every (well 99.99...% of them) astronomical picture I look at.
The area covered by the Bird must be very small as the picture came from a clever analysis of data from Hubble and a new South African telescope, but it would greatly enrich the wonder of this achievement if we were told just how tiny it appears in the sky.
I have posted this as a question, I would really like to see, and sign up to, a petition to demand that astrophotographers correct this strange policy.