SPA Comet News, August 2002
Comet 153P/Ikeya-Zhang was the star of the show during spring and was followed by a couple of further amateur discoveries. 2002 E2 (Snyder-Murakami) was a telescopic object, however 2002 F1 (Utsunomiya) reached binocular visibility. It was never an easy object, staying fairly close to the Sun, however once it moved into the evening sky a few observers managed to locate it. Many observers have sent in observations of the two brighter objects, including Mark Allison, Paul Brierley, Steve Collier, Mike Feist, Stephen Getliffe, Shelagh Godwin, Paul Harper, Edward Horsley, Cliff Meredith and Brian Woosnam. Mike Feist put together all the observations of Ikeya-Zhang made by members of the Foredown Tower Astronomy Group into a special issue of their newsletter. This records observations made between March 1 and May 22, with observations on 57 days during this period!
There were a couple more amateur discoveries in late July. First Sebastian Hoenig found a 12th magnitude comet by accident. Although he has done some comet searching, this was just a spot of casual star gazing following a spell of poor weather. Luckily he recognised a fuzzy spot that shouldn't have been there and followed up his observation. This object should become a binocular object and tracks rapidly north through Cepheus, passing 10° from the Pole on August 18. It continues down through Ursa Minor, across Draco and into Ursa Major in early September. It should remain at around 9th magnitude until mid October. Interestingly it is the first comet discovery from Germany since 1946.
This may well be the last amateur discovery as now that the SWAN images are widely available, the combination of LINEAR and SOHO should mop up the vast majority of comets. The situation will become even worse in the next few years when a project called PanSTARRS comes on line. This is an all sky survey instrument, which will cover the majority of the northern sky down to 24th magnitude and expects to find perhaps 100 comets a year. It will also find supernovae, putting this area of discovery out of amateur reach as well.
The next was an equally unusual discovery. Japanese observer Masayuki Suzuki was checking all sky images from the SOHO SWAN instrument (which views in the ultraviolet) when he spotted a moving object. Ground based observers were able to confirm the find, which is only the second SOHO discovery to be observed from the ground. It is quite close to the Earth and as a consequence moves quite rapidly across the sky. Currently approaching Orion it moves rapidly through Gemini and reaches its most northerly point in Leo Minor around August 25 (though at this stage the orbit is a little uncertain, so the track may change). Like comet Utsunomiya, it never strays very far from the Sun, but should be an easy binocular object and will perhaps gain naked eye visibility. As you can guess from the track, it is initially an early morning object, but should be visible in the evening sky during the last 10 days of August. So far it hasn't been named, but will probably be comet SOHO.
Do try making magnitude estimates of these comets. Estimates are done in a similar way to variable star observing, however a fuzzy comet looks very different to a star. The answer is to put the comparison stars out of focus, so that they appear similar to the comet. The trouble is that this makes the comet even more fuzzy, so you have to remember how bright the comet appeared to be, before you put it out of focus. The first time you try, the technique will be very difficult, but with practice it gets easier. As with most things if you don't try it certainly won't get easier! The recently published 2nd edition of the BAA Observing Guide to Comets has lots of helpful tips for beginners as well as for experts and tells you everything you need to know about making a comet observation - or even just how to find a known one. Also produced for the BAA is a The Comet's Tale a twice-yearly newsletter that summarises recent observations and discoveries and the latest scientific studies. SPA members are welcome to subscribe at the rate of £5 for two years.
For more information on current comets and the latest updates on comets Hoenig and SOHO see my web page at http://www.ast.cam.ac.uk/~jds