Comet C/2010 V1 (Ikeya-Murakami)

First of all, a hearty congratulations to both Ikeya and Murakami, both of
Japan, for this visual comet discovery last week. It is good to see that visual
comet hunters still find comets.

It appears that this comet is in direct orbit, outside our orbit, and it
brightened while behind the sun, until increased elongation in the morning sky
brought it into dark sky. This occurred while we began to catch up with it in
our orbit around the sun. This is somewhat similar to my comet find of 2004,
which has a direct orbit and a q of about 1.2. This is one of two or three
types of orbits in which visual comet finds can still be made.

There is also some evidence that Comet C/2010 V1 outburst shortly before
discovery.

Whenever a bright comet is found I run its orbit backwards to see if it was in
any areas that I have visually swept recently. Indeed this one was.

On October 18.5, 2010 UT, with my 18.5" (0.47) reflector, from my home here in
Colfax, CA, I swept, with an alt-azimuth mount, an area with beginning corners
at 12h 00m, +15 degrees and 11h 15m, 00 degrees, and an hour later was at ending
corners at 12h 50m +15 degrees and 12h 03m, 00 degrees. On that morning the
comet was at 11h 52m, +3.5 degrees, 28 degrees from the sun, and not by any
bright stars. For the whole session I stayed between 8.5 and 9.5 degrees
altitude. I picked up Messier Objects 58, 84, 86, 87, 88, 91, and NGC objects
4254, 4216, 4473, 4461, 4478 and 4578 but did not see the comet. I would expect
that it was fainter than magnitude 11 at that time. This can give us some
baseline as to its faintness two weeks before discovery.

By the way, on November 3.5 UT, between the discovery of this comet by Ikeya and
Murakami, I swept between 0 degrees and -15 degrees declination, stopping about
10 degrees above the comet's position. On that morning, I was delayed for a
short while when I stumbled across a fuzzy object that was not on my star atlas
or Sky Commander, it turned out to be a magnitude 14.5 galaxy known as MCG
1-28-4, aka PGC 32681. But if I had not spent the 25 minutes checking it out
and making my drawing, I still would have not swept all the way down to the
comet's position. The thin crescent moon was about 8 degrees from the comet at
that time.

Comet outbursts or rapid brightening prior to discovery are not uncommon, and
several of the comets that I have found probably did so shortly before
discovery. Several that come to mind are 1985e, 1986e (P/96), 1988j (all 3 of
those were short perihelion), 1992k, possibly 1994p (P/141) and perhaps my last
comet, 2010 F4. This last one was observed for only a short arc, and when it
entered the Southern Hemisphere in June of this year, only one effort was made
to image it, and it was not found. So either it had dimmed significantly, or
was off its orbital path, or both. We'll never know.

Another recent visual comet discovery, Comet Levy, 2006 T1, discovered near
Saturn at magnitude 10 on October 2, 2006 by David Levy, also appears to have
brightened rapidly shortly before discovery. On one and perhaps two occasions
in the three weeks before discovery, I swept over it, while finding much fainter
objects. Then, after discovery, it dimmed fairly rapidly. A short orbit comet,
it has been around for decades, and missed by all of us.

The fact that comets can rapidly outburst, that they are unpredictable in this
way, gives the visual comet hunter who can cover fairly large areas near the sun
a chance of continuing to find comets. But they are faint, 2 of the last 4
visual finds being magnitude 11-12, one at 10 and this most recent one at 8-9,
apparently.

Again, congratulations to Ikeya and Murakami for this fine find.

Don Machholz
Colfax, CA