BAS Club Night: March 16 2007
Herschel Society
Organiser: Mike Cowles

The speakers at Mike’s club night were three visitors from the Herschel Society in Bath, on the understanding that the Bristol Astronomical Society would reciprocate at some time in the future.

Rodney Hillier, one of the BAS vice-presidents, opened proceedings by setting the scene for the following talk on spectroscopy. He briefly outlined the theory behind absorption and emission lines in spectra, reminding the audience that pretty much everything we know about stars and other celestial objects is derived from studies of their spectra.
In particular Rodney outlined how the chemical composition of gases (for example stellar surfaces and nebulae) can be determined as well as how an analysis of spectral lines gives the best indicator of temperature.

The second speaker was Steve Kimmins who explained how, from a relatively light polluted site near Bath he could, with modest equipment, capture the spectra of many stars and identify many of their absorption lines with considerable accuracy. Although he has only been using this equipment for about a year Steve was able to demonstrate excellent results for a range of stars and other objects, such as Vega, various Wolf Rayet stars and emission nebulae such as M42 and M57.

The final speaker, Dick Philips, continued the theme of the talented amateur with a highly entertaining talk on measuring the Sun.  This talk, sprinkled with dry humour and wit, made one think what it must have been like trying to do astronomical measurements in the middle ages, although it is unlikely that Tycho included cardboard tubes and gravestones among his astronomical equipment!
Finally Rodney returned with one of his favourite puzzles – namely why is the Sun in the wrong place relative to the Moon? This refers to the fact that if one observes the Moon particularly around first quarter the position of the Sun appears wrong relative to the illuminated portion the Moon. To illustrate that this is largely due to perspective Rodney brought along a cardboard cut-out of the Moon and a piece of string. At this point one almost expected to see Valerie Singleton, Peter Purves and the Blue Peter dog appear!

Overall this was one of the most entertaining and enjoyable club nights that this author has attended and showed that the joy of astronomy does not depend upon having the latest and best gadgets!