Download FITS images for given region

[cdeil]

Feature request from Dirk Pandel at the Gamma 2016 poster -- for a given region, have a "download as FITS image" button.

I completely agree, I would use that as well.

It's not clear how to implement it, it might be very complicated and require lots of development effort in Aladin Lite in JS.
Maybe we could provide a Python script that takes a given view (encoded as a URL or JSON blob) and generates the FITS images.
This could then be exposed as a separate or built-in web service, or, for now, have to be run locally on their computer by the user.

[cdeil]

I'm not sure if there's a way to do it from our website.

But at the least we should point users to https://hips.readthedocs.io and https://github.com/cds-astro/ipyaladin from our docs, which will let them do this.