As Halley's Comet approaches the Earth for perihelion on 9th February 1986 we are due to be inundated with programs explaining facets of its passage, if the fact that two have recently thudded onto my doormat is anything to go by.

This program will be history when the Comet recedes into the distance (unless you're around in 76 years time) and at present is either intended for experts or should have a much more comprehensive and simpler insert. What do Gibbons, RA/Dec (1950.0 epoch) and azimuth mean, for example, and who knows their latitude?

There are 10 animated, interactive screens covering every aspect of the comet from January 1984 to December 1986 with copying facility. Five colours represent atmospheric light conditions from daytime to nighttime and flashing arrows warn if these could spoil the view.

Colourful LOADing screen leads to explanation of symbols used and a menu of eight options: the full 76 year orbit; close encounter orbit; Comet magnitude brightness; visibility at two latitudes; data listing and plotting; starmaps; skygraphs and local skylines.

The insert states that you don't need to be an astronomer to enjoy it - but it must surely help understand it. Forgetting that it accepts February 31 st - what does the Zenith/Nadir portion of the starmap screen show - even after "swop"? You will see the listing a lot - so learn "to restart GOTO I" .:

And, why suddenly alter control keys?

A good try, but not really a program for those with no starting knowledge.

T.W.