The words "Red Dwarf" probably make you think of a comedy programme, and "White Dwarf" a role playing game magazine (depending on how mis-spent your youth was). However, if your mind immediately leaps to images of dwindling stars instead, you'll probably be pretty familiar with Maris' RedShift series.

It's the consummate astronomy reference guide for the PC, and is a veteran package which has just progressed through to a fourth incarnation. Aimed at both novices and experts in the field, Redshift 4 features informative lectures and incredibly detailed star charts of the night sky.

The star charts are the central tenet of the program and they really are impressively implemented, boasting far greater level of detail than previous versions of the software. If you want to know the exact foundations of Redshift 4's charts, they're based on the new Tycho-2 star catalogue and the Hipparcos catalogue (with the Hubble Star Guide used for the more distant stars), but suffice it to say they are most thorough.

You can turn display data on or off, so comets, asteroids and other celestial objects can be shown, but it's not wise to try to view too much at a time, as the star charts can scroll quite jerkily even without these extras. In fact this is one area where Redshift 4 does let itself down a little; the jerkiness is evident even on a reasonably fast (700MHz) processor.

Aside from the new, more detailed maps, it's now possible to view stellar events from multiple viewpoints (for example, you can open several windows and watch what an eclipse looks like from the sun, earth and moon at the same time). The program's interface has also been tweaked to make it easier to use and indeed it is, aside from the aforementioned bugbear of the imperfect map scrolling.

All the backbone which made Redshift 3 a quality program is also present, including the Sky Diary (which catalogues important stellar events by date) and the superb photo gallery (which features many new updated images - and some of these photos are breathtaking). An interesting selection of lectures on various subjects astronomical rounds the program off with a worthy flourish.

Excellent, detailed star charts backed up with some rather smart additions in the form of new 3D viewing windows, interface tweaks and added visual material in the photo gallery make Redshift 4 a definite hit. The only downside to the program is the somewhat sluggish scrolling of the main maps.