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THE ASTRONOMER Electronic Circular No 2442      2008 Apr 26 17.08UT
Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise,  Basingstoke,
Hants, RG22 4PP,England.Telephone/FAX(01256)471074Int:+441256471074
INTERNET: GUY@TAHQ.DEMON.CO.UK      Backup: gmh@wdcc1.bnsc.rl.ac.uk
WORLD WIDE WEB                         http://www.theastronomer.org
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COMET 17P/HOLMES
Richard Miles: Request for CCD imaging of the inner coma / nucleus of 
Comet 17P/Holmes
Observations of the inner coma region of 17P/Holmes during its decline 
in brightness following the major cometary outburst in 2007 October have 
indicated a resurgence of inner coma activity every 45 days or so. 
Three such 'mini-outbursts' have occurred so far and, if strictly 
periodic, the fourth one is expected around April 25.

Observers equipped with telescopes of 0.25-m aperture or larger plus CCD 
camera are strongly encouraged to monitor this object which is now quite 
faint - around 17th magnitude in brightness.  In particular, very clear 
sky conditions are required and good focus to ensure that the 
pseudo-nucleus is properly resolved since the comet is now in a densely 
crowded region of Auriga close to the galactic equator.  Please observe 
unfiltered to maximise signal to noise.  Take a series of images over a 
period of 30-60 minutes as soon as the sky is suitably dark after 
sunset, and whilst the comet is fairly high in the sky.  Exposure times 
of at least 30 seconds are required but do not make the exposure too 
long such that the stars are elongated on the image.  The position of 
17P can be obtained by visiting the Minor Planet and Comet Ephemeris
Service at:
http://www.cfa.harvard.edu/iau/MPEph/MPEph.html

This is the last chance to verify the tentative 45-day periodicity 
(indicative of a very slowly rotating nucleus) before the comet 
approaches solar conjunction.  Please liaise with myself if you are 
successful and I can advise on how the images can be processed.

rmiles.btee@btinternet.com

Guy M Hurst