Comet 17P/Holmes (30 Oct. 2007 UT)

Date: 30 October 2007
Time: 2:45 UT
Instrument: 20x80 Binoculars
NELM: 6.2
Transparency: smoky sky


The above sketch gives some idea of the appearance of Comet 17P/Holmes with 20x80 binoculars under a darker (moonless) sky. The comet's outer coma, which was not seen previously under bright moonlight is now easily visible. North is approximately to the upper left; and west is approximately to the upper right in this erect-image view. The binoculars were used hand-held. A wall provided an anchor to steady the view.

A subtle 'rift' was visible along the northeastern edge of the comet's bright inner coma. The southwestern extremity of the outer coma appeared to be a bit darker and more diffuse than elsewhere. The presence of the comet's bright pseudo-nucleus was hinted at as a brighter spot near the center of this fascinating comet. For reference purposes, the sun is to the northeast (to the left at a slight downward angle from the comet).

At the time of the observation the orange (from a smoke filled sky) moon was just rising. Comet Holmes is bright and distinctly non-stellar (though still rather small) to the unaided-eye. The comet's coma has been steadily growing larger since the outburst that occurred about one week ago. One of many sources of information and images on this comet can be found at http://www.spaceweather.com/

Comet 17P/Holmes (28 Oct. 2007 UT)

Date: 28 October 2007
Time: 2:08 - 2:17 UT
Telescope: 130mm Refractor
Magnification: 111x
Seeing: Good
NELM: 5.0 (Bright Moon)
Temperature: +39 F (+4 C)

The above sketch shows Comet 17P/Holmes. South is up, and west is to the right in this mirror-reversed view. The bright, stellar pseudo-nucleus was easily visible on this night using the 5.1 inch refractor. As in previous sketches, some bright cometary material is visible on the southwest side (the side opposite the Sun) of the pseudo-nucleus. Also noted was a brighter ring near the outer edge of the comet's outer coma. This ring appeared
to be somewhat less bright to the southwest, perhaps due to the sunlight having to pass through the rest of the comet's coma in order to provide illumination.

No color was noticed at 111x; but at significantly lower magnifications the comet appeared to have a subtle, yellowish tint. The view is aesthetically more pleasing at lower magnifications; but higher magnifications (such as 111x) make it easier to see some of the details.

Comet Holmes remains very bright in the night sky and is visible to the unaided eye as a slightly fuzzy star. Even the slightest optical aid (such as a small pair of binoculars) is sufficient to reveal the non-stellar nature of this interesting comet.

Comet 17P/Holmes (27 Oct. 2007 U.T.)

At 2:06 U.T. on 27 October to the unaided-eye Comet Holmes looked like an ever so slightly bloated, pale yellow-orange star. It was definitely brighter than Delta Persei and seemed to be slightly brighter than Gamma Persei.

At 2:22 U.T. with 8x42 binoculars the comet appeared to have a slight yellow-orange color. It appeared as a small bright spot surrounded closely by a somewhat less bright coma. The bright spot appeared off-centered even at the low, 8x magnification.

At 2:31 U.T. with hand-held 20x80 binoculars (an outside wall was used to steady the view) Comet Holmes was very beautiful indeed! An off-centered (south of center) pale yellow-green bright spot was visible within a larger, less bright yellow-blue-green coma. The outermost edge of the coma seemed to have a slightly reddish tint. The comet looked very much like a planetary nebula.

From 3:08 until 3:26 U.T. I observed and sketched the comet with a 102mm SCT at 80x. The comet appeared to be a bit "fuzzier" (less sharply defined) than it was on 26 October. The central pseudo-nucleus was at the limit of visibility. Most of the time it was invisible; but from time to time it could be seen with certainty. The larger bright spot appeared shifted southwestward of the center of the coma. The outer 'edge' of the bright spot as well as the outer edge of the coma appeared fuzzier and less distinct than they appeared on 26 October. Only shades of gray were noted in this telescopic view. The comet has been steadily increasing in size ever since its sudden, unexpected brightness outburst.

The temperature at the beginning of this session was +32 degrees F. At the end it was +30 degrees F. My NELM (Naked-Eye Limiting Magnitude) was 4.9 on this (nearly full) moonlit night.

Comet 17P/Holmes was significantly fainter than Pluto a few nights ago -- too faint to be seen visually with most amateur telescopes. Then it brightened tremendously, becoming nearly one million times brighter, bright enough to be easily visible to the unaided-eye even in the presence of a full moon!

I've seen many comets; but Comet Holmes is the only one I've seen that has looked so much like a planetary nebula and so little like a comet. The current apparition of Comet Holmes will surely find its place in the astronomical history books!

Comet 17P/Holmes

Below are some recent sketches of Comet 17P/Holmes with brief notes below each. Notes are brief due to limited time. This blog has just been "cleared" so that I can once again make postings and I need to leave for my day-job in a few minutes . . .

Above is a sketch made from 1:58 until 2:10 UT on 26 October 2007. A 102mm SCT was used at 80x for this observation. North is up and west is to the left in this mirror-reversed view.

Note the tiny star-like pseudo-nucleus in the center of the larger glow and the broad, fan-shaped region south of center.

Above is a close-up of the visual appearance of the comet as seen with tripod-mounted 25x100 binoculars from 1:30 until 1:52 U.T. on 25 October 2007. North is up and west is to the right in this view.

Above is the full-field view of the comet on 25 October (1:30 until 1:52 U.T.) as seen with the 25x100 binoculars. The apparent size of the comet has been enlarged a little to better show the comet and its brightness relative to the stars in the field. Also shown is the observing form I now use for many of my sketches.