Telescope Reviews: 25x100 Dark-Sky View of Comet SWAN

I had to make yet another escape from the Sixth Circle of Astronomical Hades that is Northeast Ohio. Recalcitrant lake-effect clouds had hung around us all day, and it looked like they would cloud out any attempt at Comet C/2006 M4 (SWAN).

As it turned out, they did. We got hosed here in Canton.

Which is why I wasn't in Canton.

I went down to my comet site of chose, Salt Fork State Park, near Cambridge. This is a drive of about one hour from Canton. My only companions were my 25x100s and a pair of Celestron 10x50s. I had monitored satellite loops all day to see whether or not the excursion would be worthwhile and in the end decided to go for launch.

I was just, and I mean JUST, south of the lake-effect cloud canopy. Clouds could be covering up the northern horizon to 5 degrees up or so. Bear in mind, most lake-effect clouds are stratocumulus, so they're usually less than a mile above the ground. This put them maybe 10 miles north of my location, in the vicinity of Newcomerstown and Gnadenhutten.

What can I say about the comet? The recent news about it being in outburst convinced me it was worth an hour's drive, and it did not disappoint in the least. The comet was EASILY visible to the naked-eye. A star chart wasn't necessary, because about 1 degree of the comet's tail was visible to the naked-eye.

The next step was to figure out what the comet's integrated magnitude was. This isn't easy because you can't convert a non-stellar object into a stellar object, but you can in effect do the opposite by defocusing comparison stars. A brief description of these methods can be found here:

http://cfa-www.harvard.edu/icq/ICQMM.html

Standard procedure is to estimate the comet's brightness with the least-powerful instrument that will detect the comet. In this case, since it was obviously brighter than M13, I used just my eyes. OK, I actually used my eyes and my eyeglasses.

In this case, the comet looked VERY condensed (DC = 8), so I used the Brobrovnikoff Method. But how do I defocus something with the naked-eye? I let my glasses do the work by holding them out in front of my head to control the defocusing of the stars. Based on that method, I came up with an integrated magnitude of 4.3 for the comet.

The comet's apperance in the 25x100 Obies was simply stunning. The coma had an overpowering aquamarine tint with a nearly stellar nucleus. The coma's light gradient seemed to be more heavily concentrated towards the nucleus than any comet I've seen since Hyakutake. I saw this last on Saturday night, and it appeared to have DOUBLED in apparent size since then.

Oh, yeah, there was this little eency-weency tail. As in 3.5 degrees of it. That's a field-and-a-half in the 25x100s. What a difference 4 days makes! I could just make out 1.2-degrees of a low-surface brightness ion tail under a mag-7+ sky at Calhoun County Park, WV, this past Saturday night. Tonight, the first 1.5 degrees had unusually-high surface brightness. Overall, it was one of the more beautiful ion tails I have ever seen.

The view didn't disappoint in the 10x50s either, though the discernible tail dropped to about 3 degrees in length. Using the aforementioned Brobronikoff Method, I estimated the integrated magnitude in the 10x50s to be around 4.5, with a 12' coma. The tail in all three cases (both binos and naked-eye) was pointing at PA 035.

Salt Fork is typically good for around a NLM ~ 6.5 or so on a good night. I'd be curious to see how others in darker skies fared. And be prepared for another major outburst in the next few days. I say that because it'll be solid clouds the next three days around here

But for the meantime, I could at least take satisfaction that, at least for this round, Lake Erie lost. Which goes to show you one thing:

In Arizona, the most important instrument is one's scope.
In NE Ohio, the most important instrument is one's car.

Clear Skies,
Phil

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"Why suffer from insanity when you can revel in it?"

Wilderness Center Astronomy Club member since 1995
ICQ Comet Observer Code: CRE01
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