[BAA Comets] Recent observations

[denis buczynski]

Hello all
It is interesting to see the details of Nick James's observations of the faint comets which he 
imaged a couple of nights ago. Two things struck me, one being how faint these comets are and the 
other being the abilty of amateurs here and arounf the world, observing in conditions, which are for 
the most part not ideal, to image these faint comets regularly. Compared to the situation years ago 
when film was the detection medium we have come a spectacularly long way. I notice that in a message 
from Giovanni Sostero on Comet-ml on May 11  he invites amateurs using telescopes of 0.3m and larger 
to try and image Comet 67P C-G now, when it is as faint as magnitude 22! Giovanni is very 
experienced and would not have offered that challenge if he was not confident that it could be 
achieved. The situation of years ago, say in the era of the International Halley Watch in the mid 
1980's there was a real sense of acheivement when a comet of 14-15 magnitude was succesfully imaged 
by amateurs. This usually happened only after very long offset manually guided exposures were made 
from inside the interior of a dark and cold observatory. The fact that such faint comets are now 
easily imaged via a few clicks of a PC mouse whilst the observer is sat in a warm control room means 
that more of these faint comets can now be followed by amateurs.

Another matter of interest has been the imaging of the recent outburst of Comet 29P by amateur 
observers using the 2m Faulkes telescopes. These show the now familiar fan shaped outburst inner and 
outer coma. This seems to be a regular feature of the appearance of this comet in outburst. I wonder 
if the reason is that the outburst location on the surface of the comet is always the same, and that 
there is some weakness or fracturing that regularly occurs there. What causes these outburst to 
happen on such a regular basis and why do they look so similar each time? Perhaps someone on this 
list can offer a comet physics lesson and explain the causes that are thought to be behind these 
outbursts? A detailed image of the latest outburst in to be seen here at this link from Erik 
Bryssinck who posted this image on Comet-ml on May 11.
http://www.astronomie.be/erik.bryssinck/recent_work.html


Denis