[AZ-Observing] Re: Comet C/2007 N3 (Lulin)

  • From: "Rick Tejera" <saguaroastro@xxxxxxx>
  • To: <az-observing@xxxxxxxxxxxxx>
  • Date: Sat, 10 Jan 2009 10:03:19 -0700

Jeremy,

Having to get up at 040 every day for work, I doubt, I'd have made it, even
with the opportunity you describe :), so I'll live vicariously through your
observation, which BTW, is just like being there. You're a gifted observed
and a more gifted sketcher.

Thanks for sharing


Clear Skies

Rick Tejera
Editor SACnews,
Public Outreach Coordinator
Saguaro Astronomy Club
Phoenix, Arizona
www.saguaroastro.org
saguaroastro@xxxxxxx 

-----Original Message-----
From: az-observing-bounce@xxxxxxxxxxxxx
[mailto:az-observing-bounce@xxxxxxxxxxxxx] On Behalf Of
jeremy@xxxxxxxxxxxxxx
Sent: Friday, January 09, 2009 17:41
To: az-observing@xxxxxxxxxxxxx
Cc: jeremy@xxxxxxxxxxxxxx
Subject: [AZ-Observing] Comet C/2007 N3 (Lulin)

What does it take to get me out of bed at the abominable hour of 4 AM? Comet
Lulin, I guess! I've been hearing some interesting reports about it, and saw
a fantastic photo by Karzaman Ahmad at Spaceweather.com. So I was motivated
enough to overcome the horrors of such an early morning.

I was hoping to make my first observation of C/2007 N3 (Lulin) before the
full/waning-gibbous moon overpowers it for the next couple weeks. I drove
out to Sunset Crater National Monument and arrived there shortly after 5 am
with the moon blazing away and lighting up the snow-covered landscape. The
head of Scorpius was rising, and Antares was flickering with a rusty light
just over the tops of the cinder cones. While the sky was still bright with
moonlight, I shot a few photos of the landscape, and then set up my 8 inch
Dobsonian.

The comet was a snap to find at low power (37.5X) and readily pierced the
moon-washed star field as a round glow with a nicely condensed core. I'd
estimate the degree of condensation as 6. Initially, I saw probably about 2
arc minutes of the core region. The bright 6th magnitude star, 47 Librae
anchored the east side of the field.

As the moonlight began to dwindle and the comet rose higher in the sky, more
structure began to appear. Compared to the neutral gray background, the
comet emitted a very slight aqua tint. A definite brightening proceeded
eastward away from it at a PA of about 100 degrees. This extension (likely
the dust tail?) was visible out to about 9 arc minutes from the core.

As conditions improved, the coma also appeared to blossom a bit more to a
diameter of about 6 arc minutes. At this point, the brighter core took on a
more elliptical shape that preferred to drag off to the east. On the west
side of the comet, a much fainter extension (the ion tail?) emerged from the
coma at a PA of about 290 degrees. A quick look at 240X showed the coma to
be brighter along its southern half, perhaps due to the dust tail fanning
widely behind and to the south of the comet. I didn't spend time trying to
compare the comet's brightness to nearby stars, but it was definitely
brighter than 8th magnitude M107--I'd estimate by at least 1.5 if not 2
magnitudes. That's a very rough estimate, so don't rely on it for anything.
But if correct, that would put it around 6th magnitude, at the threshold of
naked-eye visibility under a dark, transparent sky. I did not actually try
to spot it naked eye, however (it would have been tough with 47 Librae right
next door anyway).

The extended details I observed were very subtle and required much time
spent observing with averted vision. Scope tapping, sweeping, and moving the
core outside of the field of view on different sides, all helped to bring
these structures into view. With strong moonlight, light pollution, or murky
skies, they are likely to be invisible while the comet is so low. The
central core however is quite bright and should be visible telescopically
and with binoculars to some degree under poorer conditions.

The time between moonset and the beginning of morning twilight was fleeting,
and the gradually improving view halted, and began to quickly deteriorate. I
spent probably 15 minutes plotting the star field, then a half hour
sketching and examining the comet for structure, and a final 15 minutes
trying to eke out the last, faintest bits of detail. It was an hour very
well spent. I attempted to track down the pairing of the nearby comet C/2008
X4 (Christensen) with globular cluster M107, but was only successful in
spotting M107. I wasn't able to spend much time on that side trip, since I
needed every bit of attention for Lulin, and I'm glad I made that choice.
Hopefully, Lulin will be quite a bit brighter in two weeks when the new moon
cycle returns and this comet's beautiful features will be easier to detect,
and rich with developing structure.

The full report and a larger sketch can be found here: 
http://www.perezmedia.net/beltofvenus/archives/001300.html

Clear skies,
Jeremy Perez
http://beltofvenus.perezmedia.net
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