Ginga: Ginga is a viewer for astronomical data FITS (Flexible Image Transport System) files. The Ginga viewer centers around a new FITS display widget which supports zooming and panning, color and intensity mapping, a choice of several automatic cut levels algorithms and canvases for plotting scalable geometric forms.
Astropy Affiliated Packages: There are several "affiliated" packages which, according to the Astropy web site, "...is an astronomy-related Python package that is not part of the astropy core package, but has requested to be included in the Astropy project". These include:
Montage-wrapper: Python module that provides a Python API to the Montage Astronomical Image Mosaic Engine.
Ginga: A viewer for astronomical data FITS (Flexible Image Transport System) files.
APLpy: APLpy (the Astronomical Plotting Library in Python) is a Python module aimed at producing publication-quality plots of astronomical imaging data in FITS format.
CASA and CASA Guides: Common Astronomy Software Applications - reduction of VLA and ALMA data
sunpy: The SunPy project is an effort to create an open-source software library for solar physics using the Python programming language.
PySpecKit: An extensible spectroscopic analysis toolkit for astronomy.
PyAST: A python interface to the starlink AST library. Do so very useful stuff like image resampling and flux conserving rebinning.
pysofa: A Python module for accessing the International Astronomical Union's SOFA (Standards of Fundamental Astronomy) library from python. SOFA is a set of algorithms and procedures that implement standard models used in fundamental astronomy. pysofa is not a port of SOFA routines but a wrapper around the SOFA_C library. Thus, no calculations are made by the pysofa software, they are all delegated to the underlying SOFA_C library.
SWarp: SWarp is a program that resamples and co-adds together FITS images using any arbitrary astrometric projection defined in the WCS standard.
yt: Analysis and visualization of volumetric, multi-resolution data from astrophysical simulations, and radio telescopes.
Blender: Non-traditional but powerful 3D package for visualization with a Python API (Tutorials)
scikit-image: Package for imaging processing in python. Toolkit for SciPy that is billed as an extension for scipy.ndimage.
galpy: Galactic and Milky Way dynamics. galpy supports orbit integration in a variety of potentials, evaluating and sampling various disk distribution functions, and the calculation of action-angle coordinates for all static potentials.