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Computers now play significant roles in our daily lives. Mobile telephones, digital TVs, set top boxes, and even some washing machines use some form of microprocessor/computer. The field of astronomy is no different. Motor driven telescope mounts are typically controlled via handsets containing microprocessor/computer systems thay give us accurate tracking of the stars. 'Goto' operation is also possible which allows a telescope to be automatically slewed to view an object that has been selected from a catalogue held within the handset, or according to user specified RA and DEC settings.

These computerised handsets are pre-programmed and do not require any additional software to be installed. Technophobes need not worry!

Many of us own a laptop or a desktop PC. This opens up a wealth of possibilities for astronomy. The number of Internet sites showing information relating to astronomy is quite simply astronomical!!!! So choose your favorite search engine, then go and explore.

There are many astronomy related applications/programs that can be run on a computer. Computers running Microsoft Windows, MacOS, and Linux are provided for. I've described just a few of these areas below.

Planetarium programs

Under the section "Where to start", I referred to a device known as a planisphere. This device shows a star map that can be set to display an impression of the permanent features of the night sky at a particular date and time. The number of features shown is limited by the relatively small physical size of the map, and of course, it cannot show non-static objects such as the Moon, planets and comets.

Imagine having a map that includes so much information that the locations and details of many thousands of stars are available, along with the current positions of the Sun, Moon, all of the planets, and many comets, and that these positions are continuously updated in real time! That's a lot of information, but it can be made easily available via a computer based planetarium program. Some of these are commercial programs, but there are a number of freely downloadable programs. I shall refer to only a few of these which are very good. Some are are capable of being much more than just planetariums.

Stellarium can be found at: and is available to run under Microsoft Windows, Mac OS, and Linux. The default star catalogue contains information about over 600,000 stars. There is an extra catologue which referes to over 200 million stars!

The screen display shows a detailed 3D impression of the sky. In my experience, Stellarium does need a reasonably powerful computer and graphics display to run well. Stellarium can be used to control telescope mounts via ASCOM (see below).

Hallo Northern Sky (also known as HNSky) can be found at: and is a Microsoft Windows program. It is not available for other operating systems. HNSky can be run under the Linux oprating system via 'wine', but some of the ancillary facilities might not work 100%. Check this out at:

HNSky provides a more conventional star map display than does Stellarium and does not need such a powerful PC to run well. I have run HNSky successfully on an old laptop containing a 700Mz processor, 512MB of RAM, and a 2D graphics card. Stellarium was not workable on this machine.

Like Stellarium, HNSky can be used to control telescope mounts, etc via the ASCOM package. I have used this combination to control my EQ6 mount. Imagine having 'Goto' at the click of a mouse button!

Cartes du Ciel can be found at: and is available to run under Microsoft Windows, MacOS, and Linux. Cartes du Ciel can control telescopes, etc using ASCOM under Windows and INDI under Linux. Refer to the Cartes du ciel website for further information.

Celestia can be found at: and is available to run under Microsoft Windows, Mac OS, and Linux. According to this website, "Unlike most planetarium software, Celestia doesn't confine you to the surface of the Earth. You can travel throughout the solar system, to any of over 100,000 stars, or even beyond the galaxy."

There are many add-ons for Celestia, but unlike Stellarium and HNSky, it cannot be used to control astronomical equipment.

Computer control of astronomical equipment and cameras

This section is perhaps not of immediate interest to anyone about to begin with astronomy. It is intended only to provide an indication of possibilities.

Electronically controlled equipment used in the field of astronomy is typically provided with 'stand-alone' software that allows for either direct control, or with the aid of 'plug-in' drivers, for use from within other application software. The former allows manufacturers to have very close control of their products. The latter allows users to integrate control of their equipment into an overall control system. There is often little standardisation here.

However, there are more standardised approaches. An example is the ASCOM project which is described as ".... a loosely-knit group of astronomy software developers and astronomy device manufacturers devoted to vendor-independent plug-and-play control. ASCOM is a many-to-many and language-independent architecture, supported by most astronomy devices which connect to computers."

Quite a mouthfull! Briefly, ASCOM can work with many planetarium and other programs to provide control of telescope mounts, focusers, cameras, filter wheels, and observatory domes. Each of the devices to be controlled must have a 'plug-in' driver to be added to ASCOM.

Perhaps the best way to appreciate the power of ASCOM is to install it along with a compatable planetarium program such as HNSky, then have a look at the default drivers that are available (from the main menu within HNSky, goto Screen>ASCOM Telescope Driver). The ASCOM site includes drivers for many more items. To get a flavour of what can be done, have a look at the EQMOD project that provides a driver for controlling Synta type telescope mounts via ASCOM.

Presently, ASCOM is a Microsoft only package. Users of other operating systems are not yet so well provided for. ASCOM have begun an initiative to develop for other operating systems including Linux and MacOS, but no dates have been given for this. Linux users already have INDI which is similar to ASCOM.

Webcams for astronomy

Webcams for astronomy? How can these simple and inexpensive devices help an astronomer?

Quite well actually! Until the deployment of telescopes in space orbits around the earth, some of the best images of the Sun, Moon Mars, Jupiter, and Saturn were produced by amateur astronomers using webcams.

To use a webcam with a telescope, it is necessary only to unscrew/remove the original lens and in it's place, fit an adaptor that can be inserted into the eyepiece holder of a focuser, connect to a PC and go!

Most webcams are supplied with software that will capture a stream of images as an AVI file which are normally played back as 'movies'. For astronomical purpose it is usually better to use dedicated capture software such as wxAstroCapture. The resulting AVI files are processed via Registax or similar software that is able to analyse each frame, select the best frames, and then align them so that they can then be stacked into a single image. The alignment process can allow for atmospheric disturbances that cause indevidual frames to be 'moved about. This effect can be seen via an eyepiece. At high magnification, images will be seen to be dancing around in the field of view. The finished/stacked images are typically clearer than can be produced by dedicated astro cameras.

Webcams have been modified to allow them to do long exposure photography, but that's another story -- refer to the section on Astro Projects.