17P / Holmes – OCT 27, 2007

Observation Notes:

Due to extreme sleep deficit, I had to pass up detailed observing and sketching this comet tonight. To the naked eye, it now is clearly non-stellar and appears as an extremely tiny disc. Through binoculars, it is slap-in-the-face obvious and cream colored. Through the low power 48X view, it now appears about as large as it did at 240X just 3 nights ago. The overall structure is similar to what I saw last night, although a new soft disc of brighter material seems to be clearer in the center surrounding the condensed fan structure. The outer halo still appears mottled. It’s grown large enough that it’s about ready to outgrow the 120X view.

Measurements with my astrometric eyepiece tonight yield:

  • central condensation: 52 x 77 arc seconds
  • coma: 310 arc seconds / 5.2 arc minutes
  • outer halo: 682 arc seconds / 11.4 arc minutes

The moon is starting to slip away, so as it grows larger and the surface brightness starts to drop it should be a great time to observe under dark skies.

Subject 17P / Holmes
Classification Comet
Position* Perseus: [RA: 03:50:00.8 / Dec: +50:21:11]
Size Central condensation: 52 x 77 arc seconds
Coma: 310 arc seconds / 5.2 arc minutes
Outer halo: 682 arc seconds / 11.4 arc minutes
Brightness* ~ 2.5 vMag
Date/Time October 27, 2007, 10:30 PM
(October 28, 2007, 05:30 UT)
Observing Loc. Flagstaff, AZ – Home
Instrument Orion XT8 (203 mm dia./1200 mm F/L)
Eyepieces/Mag. 25 mm Sirius Plössl (48X)
10 mm Sirius Plössl + 2X Barlow (240X)
12 mm Meade Astrometric + 2X Barlow (~200X)
Conditions Clear, calm, gibbous moon
Seeing 3/10 Pickering
Transparency ~ Mag 4.5 NELM
*Sources Aerith.net; Starry Night Pro Plus 5

*Based on published data.

7 Replies to “17P / Holmes – OCT 27, 2007”

  1. Jeremy:
    I’ve really been enjoying your entries on 17P/Holmes. I made a sketch myself on Wednesday evening (October 24) with my own XT-8. I’m thinking tonight I might break out my 22-Inch Dob for a better view. 🙂 I posted my sketch and a MegaStar field breakdown on my blog, including a link to your digitizing tutorial and to your Astronomical Sketching book on Amazon. I have that on my Christmas wish list, incidentally.
    Keep up the good work!

  2. Jeremy,
    Sorry you don’t the time to study this comet as much as you’d like to. It is a remarkable object.
    Last night Peter and I set up our refractors (102mm & 76mm respectively) and showed Comet Holmes to many pedestrians in New York City’s Central Park.
    When I first set up the scope at 7:30pm EDT and viewed the comet with a 12mm (40x) wide angle eyepiece I was very impressed. Bright pseudo nucleus with a large non-symmetric coma. A curious feature was obvious on the outer portion on Comet Holmes’ pseudo nucleus.
    In the refractor at the 3 o’clock position along the psuedo-nucleus’ edge was a bright starlike point. At first I thought it was a background star but it remained with the comet the whole evening until we left shortly after 1:00am. My scope uses a star diagonal and west was towards the 11 o’clock postion in the field of view. This feature appears to be in the direction of its movement – north. All observers at the eyepiece were able to pick out this feature fairly easily.
    I’m looking around to see if others have observed this event and how long it may’ve been around. I was hoping you had viewed and sketched this feature at some point.
    All the best.

  3. Fiske, thanks! I sure hope you get a chance to aim that monster dob at the comet. The care and level of detail you put into your sketch and report are excellent. Thanks for linking to the book 😀 I hope you enjoy it when you get it.
    Take care,

  4. Hi Ben, hopefully I’ll get a chance to spend a little time on it tonight. I did not notice the feature you mentioned, but another observer, Eric Graff appears to have seen a separate stellar feature besides the pseudonucleus itself (he also picked up a lot of other fine details!). His sketch is rotated to put north at the top, but have a look and see what you think. Was that what you saw?
    Looking forward to going at it again shortly!

  5. Jeremy, The link to the sketch by Eric brings up a blank screen on the Cloudy Nights site. I checked out your list of links and the same thing is happening there.
    Looking forward to his sketch of the comet.

  6. Ben, I’m not sure what’s happening there. I double-checked the link and it seems to be working. I also logged out of the Cloudy Nights site to be sure it wasn’t a login-specific problem, but the link still worked.
    You may want to just go directly to cloudynights.com, go to the forums, and then find the “Planetary and Solar System Observing” section. In that section, look for the “ALERT – Comet 17/P Holmes in mega outburst ” thread. Besides a wide range of amazing photos and sketches, Eric (aka Cildarith) has a post on Oct. 28 at 6:50 PM PST with a link to the sketch. Hopefully that will get you there…it’s incredible.

  7. Jeremy, Thanks for the thread location. Both your 120x sketch posted on the 29th and the image in the post below show the effect we saw:
    SleepIsWrong (sage) Re: ALERT – Comet Holmes in mega outburst – 10/28/07 05:44 PM
    This bright starlike object was on the side opposite the side where the coma appears compressed.
    Also noticed at the eyepiece by many was a darkening in the coma on the side of the bright point shown well in the latest images & sketches on that thread.
    Thanks again.

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