When Mars was closest to the Earth in August 2003, the Macclesfield Astronomical Society held a star party at Jodrell Bank Observatory with quite a number of telescopes set up to observe it. As the evening progressed a consensus arose that two scopes were giving particularly good images: my own FS102 4-inch Takahashi Fluorite Refractor (at around £3500, or $5000, with its mount) and an 8-inch Newtonian on a simple Dobsonian mount newly bought for just £200 ($300). I personally preferred the view through the f6 Newtonian but others thought that the f8 FS102 gave a slightly better image, so we will call it a draw. It is worth discussing why these performed so well and, just as importantly, why perhaps the others did not.

The majority of scopes had been set up on a large concrete patio outside our visitor centre, but the FS102 and Dobsonian were on grass and not observing over the patio. This, I believe, was the major reason these two scopes had performed so well. During the day (remember it was August) the concrete would have absorbed heat, which was then released during the evening, causing localised air turbulence through which the scopes mounted on the patio were viewing Mars. It is not, therefore, surprising that the two mounted on grass performed better. One of the world’s top solar telescopes, the Big Bear Solar Observatory, rises out of a lake so that it is almost totally surrounded by water in order to minimise any local thermal effects. One of my friends went to Egypt to observe the transit of Venus in 2004. It was very hot in the holiday complex, and he said that it would have been nice to observe from the shallow end of the swimming pool. I suspect that, had he done so, he would have had steadier images too! An obvious piece of related advice is that when observing the planets, particularly in winter, one should not observe them over rooftops, as the turbulence caused by the escaping heat will severely degrade the image. Peter Shah, one of the country’s leading astro-imagers, whose beautiful image of M31 is shown in Plate 15.8, has recently lagged the concrete pier on which his telescope is mounted to improve its imaging quality!