Sunrise Sunset is a Python package that can determine the sunrise and sunset based on a given altitude zenith. It has two public methods. The first returns the sunrise and sunset in a tuple. The second returns True or False depending on whether the supplied date/time is during the night or day. The constructor takes three arguments, a date, latitude, and longitude. There is one keyword argument for changing the default zenith, which is set to "official". The zeniths are "official", "civil", "nautical", "amateur" (astronomical), and "astronomical". It does not rely on third party packages, but you may need something like pytz to create dates with timezone info.
Nova is a free Integrated Observational Environment for astronomers. It combines Ephemeris functionality with the capability of controlling modern "goto" telescopes and popular CCD cameras. Nova combines image capture, telescope control and ephemeris functionality into a single application. The main goal of Nova is to make it easy(ish) to capture CCD images of objects with a good degree of accuracy. Nova is also able to manage several kinds of astronomical database (i.e GSC, USNO, SAO, etc.) and makes it easy to automatically schedule observational activity through the use of target object lists.
GRALE is a set of tools - a library and a number of accompanying applications - to study gravitational lenses. Gravitational lenses are astronomical objects so massive that their gravitational pull even deflects light rays. This can cause multiple copies of the same background object to be visible, like a cosmic mirage. The locations and shapes of these copies can provide information about the mass distribution of the gravitational lens, which GRALE can help recover using a genetic algorithm-based method. Apart from these so-called lens inversions, it's also possible to simulate gravitational lenses.
WCSLIB is a C library, supplied with a full set of Fortran wrappers, which implements the "World Coordinate System" (WCS) standard in FITS (Flexible Image Transport System). It also includes a PGPLOT-based routine, PGSBOX, for drawing general curvilinear coordinate graticules, and a number of utility programs. The FITS "World Coordinate System" (WCS) convention defines keywords and usage which provide descriptions of astronomical coordinate systems in a FITS image header.
skyviewer is an OpenGL-based program to display HEALPix-based skymaps, saved in FITS format files. The loaded skymaps can be viewed either on a 3D sphere or as a Mollweide projection. In either case, realtime panning and zooming are supported, along with rotations for the 3D sphere view, assuming you have a strong enough graphics card.
Multi-body Gravity Simulator (MGS) allows you to perform a simulation based on a fixed time slice. Its unique features are the ability to perform realtime simulations, a three dimensional visualization of the simulation, and the ability to design simulations in XML and with a GUI. The accuracy of realtime simulations will depend on your machine speed. Fixed time step simulations are also supported.
AstroStack is an easy-to-use astronomical imaging and processing tool geared towards the use of inexpensive webcam CCDs. It provides a very tunable environment to produce the best quality images. It supports the following features: tunable webcam sampling; image stacking (averaging, additive etc.); pre and post-capture gamma (brightness) and contrast correction; dark-shot CCD calibration (subtractive); and an internal 16-bit grey-scale format for optimal resolution.