Graeme (Grey Boots) Kidd tells me that there has been some sort of major disaster every time Halley's major has poked its nose into our corner of the solar system. I have every confidence that Grey Boots is wrong but, not being the sort to leave anything to chance, I thought that I should refer to Maurice Gavin's latest work, Halley's Comet.

Halley's Comet is designed to provide non-astronomer types with a comprehensive and easy to follow guide through this forthcoming celestial visitation. The opening menu lists eight options. Option one plots the path of the comet from 1948 to 2024 giving two perspectives. The plot takes about four minutes but it can be speeded up. The second option does much the same thing except this time the scale of the map is much larger, the plot is from September 1984 to January 1987, The next three options give information on the comet's visibility. First, a graph of apparent magnitude which shows when the comet will be visible and by what means it can be viewed. For example, between now and November the comet can only be seen through a telescope but from January to May you can observe it with the naked eye alone. If you live in the Northern hemisphere and want to know for how long the comet will be visible each night, then option four will tell you. Eclipse haven't forgotten the other CRASH readers either, because option five does the same as four, except this time for viewers in the Southern Hemisphere (and a big hello to all CRASH readers who live there).

The next options produce some very useful but often complicated looking results. The computer does not calculate the data relating to the comet's position instead it looks up a table which results in a much faster response. A complete list of the the data can be called up by option six. The data table looks a little complicated because it uses unfamiliar units. RA stands for right ascension; in simple terms you can think of that as longitude on Earth. Declanation is analogous with Earth's latitude. These units are important for those of you with observatories in the garden; all that you need to do is to enter the co-ordinates and it will be set ready to let you observe the comet.

For most of us all we need to do is to be able to locate the comet by referring to the patterns made by the stars a star map can be called up via option seven. The star map produces a detailed map of the heavens marking the position of the comet according to the latitude, date and time that you enter. Underneath the map itself is a table giving the comet's position in numeric terms and Fn it's apparent magnitude. In a little box on the far right of the screen is a diagram depicting the view of the comet in relation to the horizon. This display is enlarged if you select option 3 which causes the skymap to be produced on a full screen.

I am not really that much of a star fan but I will be trying very hard to catch a glimpse of this comet. What appeals to me about Halley's Comet is that I can ask for a map that will help me find the thing, as well as work out the best time to watch. The print out option is very helpful: all of the screens can produce a hard copy so you can rush out into the garden and work out just where to look. My only serious gripe is that not enough printed information came with the program. I mentioned this to Mr Gavin and he assured me that more information would be available on request. If you do intend to make the most of this visit then buying this package could be money well spent; after all you have always got it for the next time unless of course Grey Boots is right.