[AstroPy] Some Feedbacks about Astropy

[Guang Yang]

Dear Astropy developers & users,

I'm a university student working on astronomy. Recently, I'm switching to python from IDL. Astropy is indeed an awesome tool set. But it lacks some often-used tool for astronomers compared to NASA's Library for IDL:

1. I find no tools to align two images, i.e. to uniform their astrometry, pixel scale, image size and etc.  hastrom.pro (http://idlastro.gsfc.nasa.gov/ftp/pro/astrom/hastrom.pro) is a good example to perform such a task.

2. Though there's astropy.coordinates.matching.match_coordinates_sky to cross-correlate two catalogs, it doesn't allow user to specify matching radius and matching mode (e.g., one-one match). I've made a function to do so, and hope similar function can be included in astropy (https://github.com/Guang91/Astronomers_Tool_Box/blob/master/my_srcor.py). 

Thank you,
Guang Yang