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No 58 - December 2008

Variable star observing workshop

The Variable Star Section of the British Astronomical Association (BAA) held a workshop on observing variable stars on 2008-10-18. This was aimed both at newcomers and at more experienced observers wishing to learn more about the current observing campaigns. The venue was the James Clerk Maxwell Building of the University of Edinburgh. Roger Pickard, Director of the Section, welcomed everyone and began the day with an introduction to variable stars, what types there are and why we should keep an eye on them. The BAA keeps a continuous record of observations starting in the early 20th century. Roger then gave an introduction to CCD observing of variables. The precision of CCD observations is very high; the process is computerised and can be automated.

It was then John Toone's turn to present the more traditional side that is visual observing of variables. The precision and accuracy of visual magnitude estimates is only 0.1 or 0.2 magnitudes, but observing is much simpler and a variety of instruments from naked eye through binoculars to a telescope can be used. More observers are likely to take up visual than CCD observing. In some ways CCD and visual observations complement each other, the CCD giving high precision and time resolution, the visual observations more likely to cover longer time intervals more evenly.

Then it was time for some hands-on experience. Using slide projections of the night sky John Toone took us through the magnitude estimate from two comparison stars by the fractional method. We also learnt how to record the observations and how to report them to the Section. The question was raised whether one could use survey data available on the Internet instead of the actual night sky. Such data mining would be useful, but visual observing of the real sky should continue at any rate in order to continue the existing record of visual observations.

After lunch, Robin Leadbeater opened another dimension - wavelength - with his talk about spectroscopy and variable stars. With a reasonably good grating mounted like a filter, and given a CCD or digital camera, useful results can be achieved. Higher resolution spectrographs are now also available to the more serious amateur.

Des Loughney spoke about eclipsing binaries. He is also pioneering the use of a digital SLR. Ten short exposures without tracking can reach 10 mag, and a precision of about 0.03 mag is possible. More generally, a campaign is ramping up to observe the forthcoming eclipse of the bright variable ε Aurigae in 2009 and 2010.

The programme concluded with Melvyn Taylor's talk on binocular observing. This included tips on choosing good binoculars, choosing stars to observe, and using finder and comparison charts. The binocular observer can make use even of very short periods of good weather. As with all visual observing of variables, it is important to leave 10 or 15 min for dark adaptation.

Everyone had an enjoyable and educational day. Many of the participants came from various parts of Scotland. Our thanks go to the organiser Des Loughney, Tania Johnston of the Royal Observatory Edinburgh, and also to those who made the journey from further south and who contributed to the programme of the workshop.

Horst Meyerdierks


Cover page

IYA astro-happening at Science Festival

Johann von Lamont - Bavaria's Scottish Astronomer Royal

Never the TWAN shall meet?

Total eclipse of the sun on 1st August 2008

Forthcoming events

Exoplanets come into view

Recent observations

Variable star observing workshop

Society news

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