Telescope or astronomy devices control
There are nearly as many different astronomical set-ups as astronomers. Lots of devices are required in a set-up, and many of each type exist. Many are not supported by free software. A hardware compatibility list is being done here.
Acquisition software generally have to handle high-end cameras, DLSR and focusers. Autoguiding software generally have to handle low-end cameras and telescope motorisations, possibly focusers too. They make very different tasks and address a large range of devices.
Multiple functionality software
Telescope control: Autoguiding
Telescope control: GoTo
GoTo functionality is generally managed by cartography software.
INDI-compatible cameras can be used with Ekos.
cccd is a simple astronomical CCD controller. It supports TSNK-lab ICX285AL cameras, QHY5, QHY6, QHY9, QHY8L, DSI2PRO, DSLR.
Qastrocam-g2: capture and simple guiding software for astronomy, using V4L2 acquisition. It also supports QHY5 and QHY6 cameras in release 4.9.
oaCapture is a recently created free software that features V4L2 capturing in a Qt application. It provides many image capture controls, can demosaic images and save them in SER files. Support for other cameras than V4L2 has been introduced (ZWO ASI, QHY5, QHY6, SX Lodestar, Atik ATK-16 and The Imaging Source), as well as filter wheels on Linux (Xagyl and Starlight Xpress) and it also works on Mac OS X.
Planetary Imager is a software for planetary imaging. Its goal is to be able to get a simple, fast imaging software on Linux platforms, where there are really few reliable applications. Currently supports V4L2, ZWO and QHY devices.
Standardization initiatives and remote telescopes systems
Some projects do not focus only on one particular device or even type of device, and provide abstraction layers or even try to standardize the way astronomical programs communicate with each other and with devices. An example of such an abstraction layer would be the Ascom Initiative on Windows platforms.
INDI is such a project for all kinds of devices. It is getting very popular and many devices already have INDI support. Before developing INDI, the author, Elwood C. Downey of ClearSky Institute, developed Talon, another free software for automated observatories, which is still used in several observatories around the planet.
Another software for autonomous observatories, the Remote Telescope System (RTS2), also developed an abstract device layer, enabling control of all possible combinations of mounts, CCDs, photometers, roof and cupola controllers. It is also used in several observatories around the planet.
Unicap is a way to access imagery devices, it doesn't seem to be used by many or actively developed anymore.
File format is also an important concern. Having a way to store a sequence of images in one file is very handy, in particular for planetary streams that have thousands of pictures. The SER file format aims to give a simple and strong base for uncompressed capture and processing systems for astronomy.