The Great Comet of 1996, Mir, STS-76

Walter Nissen (dk058@cleveland.Freenet.Edu)
Sat, 23 Mar 1996 16:24:26 -0500

I am horribly conflicted about posting this message.  The plainly evident 
general interest demands that it be posted, but as a guardian of list 
purity, I am pained. 
Finally, I escaped much of the light pollution to make a half decent OBS of 
The Great Comet of 1996, Hyakutake, 1996 B2. 
1996 March 23.35 UT: m1=0.1, Coma Diam=60', Tail: 17 deg in PA ~230, NE, 
Walter Nissen (Loudonville, OH) limiting mag 5.5 or 6.  Overall impact 
equivalent to the magnificent, spectacular appearance of Comet West, 1976 
March 7.  No multiple dust tails, but a striking pale blue color.  Tail to 
vicinity of eta and upsilon Boo.  Pale blue, esp near coma (esp in 11x80; 
parentheses denote binocular OBS, not lesser significance), very straight. 
(In 11x80, the curtain of ghostly, soft, blue, bright light of the coma 
and tail was almost overwhelmingly striking and beautiful).  Outline of 
comet was like a dowel with a U-shaped end, like Comet Halley, as 
distinguished from V-shape of Comet West.  This outline did not have the 
definite extent of that of Halley, the light falling off more gradually. 
Central coma was mostly star-like, no sharp gradient forming a disk, as 
on March 16.  Coma and tail merged smoothly, appearing to be a single 
light distinguished simply by convention and shape.  Coma = width of tail 
near coma.  Brightness of coma and tail dropped off steadily.  Tail was 
strong for 4/5ths of its length, then difficulty increased.  No jets or 
streamers or knots seen.  Motion was very obvious in just a few minutes. 
Seeing = good-exc, only occasional twinkle noted.  Transparency = 
good-exc, occasional minor cloud.  (In 7x35 and 11x80 B, appearance of 
comet was surprisingly similar to naked eye, main difference being 
shortening of the tail). 
Earlier, from near Cleveland, comet was prominent in Bootes, but it was 
a pathetic stub of its appearance in a darker sky. 
Details on quants:  m1 = .1 +/- .3, sequence from AAVSO Atlas, alpha Boo = 
-.1, alpha Vir = 1.0; coma = 1 deg +/- .2; tail 17 deg +/- 2. 
Light pollution is to comets like carbon monoxide is to mammals.  It's 
always with us and very small quantities are not fatal, but it's nothing 
to kid around with.  Ditto for clouds and haze.  In contrast, many 
satellites are readily visible from urban areas. 
I caught sight of STS-76 emerging from the shadow 14m 2.49s after catching 
sight of the Mir Complex at about 960323 093350.


Walter Nissen