103P/Hartley – OCT 4, 2010

Sketch of comet 103P/Hartley

Sketch of comet 103P/Hartley

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Observation Notes:

Comet Hartly has not become as bright as hoped, but it is still an enjoyable telescopic target. Clouds from the day’s thunderstorms cleared up enough that I was able to spend some time with it while brilliant flashes of lightning decorated the southern horizon. At low power (37.5X) through the 8 inch Dob, it appeared large with a diffuse coma that faded smoothly to the background. The portion I was able to see was about 20 arc minutes in diameter. At 120X, the core appeared to have a very faint, stellar point that flickered in and out with the seeing. I’m pretty sure I had this distinguished from field stars as it seemed to hold its own as the comet moved across the field. The number of field stars did make it difficult to assess any elongation, so I was unable to pick up on either dust or ion tail. I did not detect any color. The comet moved about 4 arc minutes to the northeast over the course of 75 minutes from 10:45 pm to midnight.

I followed up with a look through 15 x 70 binoculars. It is currently situated in a tangle of 8th and 9th magnitude stars, so it’s a little difficult to distinguish it from the light of these stars. Its soft glow actually makes the area look like a partially resolved open cluster. I had to make a couple trips back and forth to the computer to be sure I was in the right spot and wasn’t actually confusing it with an open cluster.

Subject 103P/Hartley
Classification Comet
Position* Cassiopeia:
0545 UT: [RA: 01 18 12.9 / Dec: 56 22 43]
0700 UT: [RA: 01 18 51.2 / Dec: 56 23 44]
Size Coma: 20 arc minute diameter
Degree of Condensation: 2/ with faint, nearly stellar central condensation
Brightness* Not Estimated
Date/Time OCT 3, 2010, 11:45 PM – Midnight MST
(OCT 4, 2010, 0545-0700 UT)
Observing Loc. Flagstaff, Arizona, USA – Home
Instrument SkyQuest XT8 (8 inch f/5.9 Dobsonian)
Eyepieces/Mag. 32 mm Sirius Plössl, Pentax XW10
Conditions Partly cloudy, calm, cool, humid
Seeing 4/10 Pickering
Transparency SQM: 20.5
*Sources Starry Night Pro Plus 5.8

5 Replies to “103P/Hartley – OCT 4, 2010”

  1. Great sketch Jeremy! I took a shot at observing 103P/Hartley on the 30th of September with my 25x100s. I know what you mean about it resembling ‘a partially resolved open cluster.’ The comet wavered just within visual perception, & I’m sure I could just make out a vague hint of colour. It’s going to be interesting watching Hartley over the next few weeks to see how it develops.
    Keep up the good work!

  2. I got it on the 4th as well Jeremy with my 6 inch Dob: very comparable view to your sketch. I know what you mean about background stars.

  3. Thanks for the reports, Ewan and Peter!
    The rich star field makes for an enticing view, but it really hinders me trying to pick out any asymmetrical structure and not be fooled by random star clumps. I hope you get to enjoy some more nice views of it.

  4. I observed Hartley on the 5th from the darker skies of Montauk NY with my 10″ refl. At 38 and 76x Hartley looked just like your drawing. Thanks for the view.

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