[sac-forum] Comet 17/PHolmes - Swan Band filter

In response to Frank Uralic's request for anyone using this kind of filter I 
can respond to a yes I have and did so last night, Thursday.  Steve Coe, a full 
moon, some bright yard lights and I were out north of Scottsdale, AZ with my 8" 
SCT at about 145X.  Without the filter this is a magnificent, yet mysterious, 
comet.  Don't know what I can supply for an observation that hasn't been said 
before.  Yes it does have obvious planetary nebula like features.  It is round, 
large, bright with an extremely brighter coma and a stellar nucleus that is 
offset from the coma.  I didn't attempt to measure its position.  With the Swan 
Band there is a much fainter fan shaped halo of about 1/2 again larger than the 
entire comet.  A surprise to me as this hasn't shown up in Jeremy Perez's 
excellent drawings nor any of the astroimages.  The comet was at about the 
focus of the halo, which is about where one would be expected.  Unfortunately I 
didn't try to measure the position angle so can't say much about that.

The Swan Band filter is supposed to make comets that consist mostly of gas 
brighter and those mostly of dust fainter.  So my suspicion is there is a 
little more gas than dust.  Yet, other than the halo, never did we see any hint 
of a tail.

Hope this helps.

Clear skies,
AJ Crayon

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