Welcome to the homepage of StarTrak, a freeware program for amateur astronomers. StarTrak runs on the Psion 3, 3a, 3c and 3mx range of handheld computers. Its purpose is to help you find and track the positions of planets, stars, galaxies and other objects of the night sky.

Latest update: 21 August 2006: Photos of 'scopes adapted for StarTrak by Mike Morrison-Smith added to website.

StarTrak - featured in the July 2000 issue of
- the UK's leading magazine for amateur astronomers.

Photos of 'scopes adapted for StarTrak

StarTrak on the Series 5, Revo and other EPOC devices

Making Setting Circles

Advice on construction

Go to the StarTrak software download page (for Psion Series 3 - 3mx)

View the StarTrak User Manual (for Psion Series 3 - 3mx) on-line

Go to the StarTrak User Manual (for Psion Series 3 - 3mx) download page

Greenwich Mean Time (GMT)

FAQs

StarTrak is a computerised database, containing information on the planets, all the Messier objects, as well as a number of other objects in the sky. For any object in its database, StarTrak can give you that object's position in two formats:

• RA (hours and minutes of Right-Ascension) and Dec (degrees and minutes of Declination) coordinates
• Altitude angle (number of degrees and minutes upwards from the horizontal) and Azimuth angle (direction in degrees and minutes from true North).

Thus if your telescope has either RA/Dec or altazimuth setting circles, it's easy to point the telescope at the object of interest. This makes StarTrak suitable for both equatorial-mount telescopes and altazimuth mount telescopes (such as Dobsonians).

The above figure shows a typical screen of information on a Psion computer running StarTrak. It shows three alternative names (M31, NGC224, Andromeda Spiral) for the same object, together with other information. If you were running StarTrak now, looking at the Andromeda Spiral, it's very unlikely that the altitude and azimuth readout would show the same values as in the figure - in fact, as the Earth spins on its axis and orbits the Sun, the altitude and azimuth of any celestial object are constantly changing. StarTrak updates its altitude and azimuth readout every second. It can do this because it knows the current time (from the Psion's clock), and from this can calculate the Earth's position in space. StarTrak also knows the latitude and longitude of your chosen observatory, and the RA (Right-Ascension) and Dec (Declination) coordinates of each celestial object in its database. StarTrak is programmed to use this information to calculate an object's altitude and azimuth (as seen from your chosen observatory), and to keep re-calculating the altitude and azimuth, which change with the passage of time as the Earth moves through space.

The StarTrak database contains a relatively small number of objects (the planets, all the Messier objects, plus a few others), but it is very easy to add objects of your choice. To add an object to the StarTrak database, the minimum information you need is the object's name and its RA and Dec coordinates. StarTrak will then be able to tell you where to point your telescope to find that object.

StarTrak doesn't display a view of the night sky, and is not intended to replace star charts. Rather, it is designed to be used with a star chart to help you find the object of interest. Point the telescope in the right direction with information from StarTrak , and compare the view through the telescope with your star chart to identify the object of interest. Of course, in many cases it will not be necessary to use a star chart - from the view through the telescope, the object you are seeking will be obvious.

The present version of StarTrak doesn't show the positions of the Sun, Moon, asteroids and comets.

The present version of StarTrak ignores

• atmospheric refraction
• precession (this is the gyration of the Earth's axis over a period of 26000 years, caused by the gravitational effects of the Sun and Moon)
• nutation (the slight wobble in the Earth's movement caused by the variation in the relative positions of the Moon and Sun)

StarTrak is particularly well suited to telescopes with Dobsonian mounts. If your telescope is a Dobsonian but doesn't have azimuth and altitude setting circles, see Making Setting Circles.

The information given at this website describes the freeware program StarTrak from ST Software, and bears no relation to any other product or program of the same name.

Your comments, questions and suggestions on StarTrak and this website are welcomed - just send an email by this link:

Feedback / questions on StarTrak

Your email address will not be passed on to anyone, nor will it be added to any email list, but will simply be used to respond to your query.

It would be interesting to know from which part of the world you observe the sky, so please include this information if you have time. Thank you!