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(meteorobs) Hale-Bopp on Feb. 15
After nearly two weeks of clouds, I finally got to see Hale-Bopp in crystal
clear skies this morning (I saw it through the clouds earlier this week).
What follows is a very detailed observation that is my first attempt to put
all of my measurements into a somewhat readable form. The third paragraph
(this being the first) could probably be skipped as I tried to produce a
rather detailed verbal picture of the comet.
The total magnitude seemed to equal Deneb (mag. 1.25 in Sky Catalog
2000.0), although, as twilight later progressed, and only the comet and the
summer triangle remained in the eastern sky, the comet was definitely the
brighter and I estimated it as magnitude 1.1. Throughout the 1.5 hour
observing session the comet displayed a naked eye tail extending about 7
degrees.
It was certainly a beautiful site, but I wasn't prepared for the view
through my 13.1-inch reflector. At 58x a bright fan of material was seen
spraying out from the nucleus. The borders of this fan extended toward PA
185 and 246 degrees. The border at PA 185 degrees extended almost to the
edge of the coma and was no doubt forming what would ultimately be the
outer edge, or right side of the dust tail, which my naked-eye estimates
indicated was at PA 310 degrees. The fan's border at PA 246 degrees seemed
more intense and definitely curved back to form the inner edge, or left
side, of the dust tail, which my naked-eye estimates indicated was at PA
340 degrees. With the nucleus at the bottom of the comet, the dust tail was
definitely extending up from the right side of the nucleus, while a much
fainter, straight and narrow tail (probably the gas tail) extended up from
the left side of the nucleus. There was a hint of a brightening at around
PA 70 degrees from the nucleus which seemed to flow back and form the
inner, or right side, of the gas tail. The outer, or left side, of the gas
tail was just an extension of the coma. When looking exclusively at the
comet's head, the two tails combined with the coma to form a rather
distinct U-shape. Between the inner edges of the two tails, the space
seemed abnormally dark, with this darkness being most notable near the
nucleus.
Overall, the U-shape, the bright fan of material, and the distinct
blackness extending between the dust and gas tails, reminded me of a
painting I had seen in a 1976 issue of Astronomy magazine. I looked through
my issues a few minutes ago and found it was in the July 1976 issue on page
46. This was the Great Comet of 1881, which had been discovered by Tebbutt.
Although the 1881 comet was a more impressive sight than the current stage
of comet Hale-Bopp, the detail of the 1881 comet's head is very similar to
the current telescopic view of Hale-Bopp.
By the way, at 200x the bright fan of material had an appearance like a
cloud, similar to what I have viewed within M42 and a few other bright
nebulae. The nucleus looked more like a 0.3 arc minute long bar than a
stellar or near-stellar object. This "bar" was perfectly situated as an
extension of the fan border at PA 246 degrees. Close scrutiny at 500x
hinted at the possibility that the western half of the bar may have been
very slightly fainter than the eastern half. The fan border at PA 185
degrees seemed to bisect the bar right at the point of the apparent change
in the bar's density.
In nearly 1400 comet observations made since 1973, this was the most detail
I have ever seen within a comet's coma. I have the feeling Hale-Bopp is
going to provide even better views during the next couple of months!
Gary