New Naked Eye Comet - 17/P Holmes

Just had a look at it for a second night, first in the binoculars and it is much bigger tonight and possibly a little brighter than last night. In the telescope it is simply stunning. Big circular coma, a point like nucleus and a quadrant of the coma showing a fan like mini tail to the west completely contained within the coma.
Gotta go and look again.......

This pretty much exactly describes what I saw this evening through my 8" Dobsonian at 50x - a beautiful, almost circular halo with a very bright, star-like point dead centre, with a bright, fan-like, short tail emanating from the nucleus but contained with the circular coma. At 100x plus I thought I could make out the very diffuse outer coma that John O'Neill described above, although it was hard to be sure with the full Moon so near by.

Does anyone have any idea at this stage what caused this comet to get so bright so suddenly?

Just managed to get a look through a gap in the clouds. Even with the naked eye you can see that it's moved towards Alpha Persei since yesterday and in 10x50 binoculars it now looks like a yellow globular cluster where as yesterday it looked like a star. Fascinating to see something change so much in a day!

Here's my full report: www.bartbusschots.ie/blog/?p=565

Bart.

Does anyone have any idea at this stage what caused this comet to get so bright so suddenly?

Nope, but I did find this:

www.astro.uni-bonn.de/~dfischer/mirror/306.html

A most amazing eruption is occuring on comet 17P/Holmes which was at 17 mag. at best but on October 24 suddenly began to brighten like crazy: Now (afternoon UTC) it has already reached 3rd magnitude and is easily visible to the naked eye, as reports from Japan indicate: "Perseus does not look 'Perseus' familiar to us due to the bright stellar object now." The comet looks like a bright, yellow star, and only magnification reveals a fuzzy coma around the dusty core. Holmes was discovered in 1892 thanks to a similar outburst, and hope is that the further development will be similar now: the coma should expand over time but stay bright for a week or more. "Following the initial stages of the [1892] outburst, the comet's total magnitude faded only very slowly and it remained visible to the unaided eye for about 3 weeks," advises comet guru John Bortle: "During this interval the coma expanded dramatically (as might be expected), reaching 20'-30' in size before its outer regions began to drop below the sky background." Moreover, there was a second outburst "of almost equal amplitude to the first one, about 75 days following its 1892 November brightening. Thus, I would urge everyone to watch very carefully for a possible repeat of this secondary event about the turn of the year."

and just one more shot..........despite the cloud, I waited for two and a half hours tonight and finally got a break to get 75 x 0.3 seconds of images. This is one weird beastie.

Hi,

The Comet 17P/Holmes is quite different last night (25/26 Oct 2007)

Naked-eye estimate mag 2.4. at 22:00 UT.

Shortly afterwards did a telescopic observation with 25cm refl. at 181x:

1. Faint diffuse halo not seen tonight.
2. Bright circlular disc halo, 2 min of arc across
3. Very Bright fan towards SW.
4. Almost stellar very bright central condensation (at centre of halo).

Unlike previous night the no longer stellar in 8x50 finder (i.e. tiny disc).

All this despite the large bright full moon nearby.
Thin cloud, but uniform

John

Hi,

1. Faint diffuse halo not seen tonight.

John

Yes, but in Phoenix's (slightly overexposed) photo above you can make out a faint outer halo.