Comet 17P/Holmes (03 Nov. 2007 UT)

Date: 03 November 2007
Time: 2:18 - 2:40 UT
Instrument: 25x100 Binoculars
Mount: Altaz/Tripod
Seeing: Good
Transparency: Good
NELM: 6.5 or better
Temperature: +27 F (-3 C)


Shown above is the full 2.33 degree field of view of the large, 25x100 binoculars with Comet Holmes near the center. West is up, and north is to the left. The sun is toward the north-northeast. Many of the fainter stars that were visible were not included in the sketch.

The comet's inner coma was sharpest and brightest on its sun-facing side. The outer coma was noticeably more diffuse, fainter, and less sharply defined than it has appeared previously.

The brighter portions of the comet (within the inner coma) were a subtle greenish-blue color. The color was initially noted with the 25x100 binoculars, but was even more apparent with de-focused 8x42 binoculars.

This comet has pretty much maintained its brightness over the past several nights. It remains easily visible to the unaided eye as a moderately bright 'fuzzy star'.

When scanning the sky with 8x42 binoculars in the general vicinity of the comet this evening I spotted the diffuse glow of the nearby open star cluster NGC 1528.

This observation was made in the evening, local time. The comet was also briefly observed and sketched on the previous morning using 20x80 binoculars.

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.

Jupiter 11 Sept. 2007 U.T.

Date: 11 September 2007 U.T.

Time: 1:35 - 1:47 U.T.

Telescope: 13cm refractor

Magnification: 138x

Seeing: Very Poor - Fair

NELM: Twilight

Temperature: +68 F (+20 C)

Shown above is my rough, at-the-telescope sketch of Jupiter. North is up. Preceding is to the right. As part of an experiment a 1.25 inch, 90-degree, erect-image diagonal was used. Also in use was a new filter wheel; but no filters were used during the making of the above sketch. The filter wheel was loaded with various filters for deepsky use; but the planned observing session was cut short due to clouds and high humidity.

Jupiter's North Equatorial Belt was the darkest feature on the planet. It had a subtle, somewhat rusty color. The other belts on the planet appeared to be blue-gray in color. The following limb of the planet was somewhat darker than the preceding limb due to the sun angle (a phase effect).

At times the seeing was very bad, leaving nothing more than the NEB visible on the planet. At other times the seeing was fair, approaching good. The seeing was both, worse at times and better at times than it was for my previous Jupiter observation; but for the most part it was better.

Jupiter & Lambda Ophiuchi

Date: 03 September 2007 U.T.
Time: 2:03 - 2:15 U.T. (Jupiter)
Telescope: 130mm refractor
Magnification: 138x (Jupiter)
Filter: Moon-SkyGlow (Jupiter)
Seeing: Poor to Fair
NELM: Twilight (Jupiter)
Temperature: +83 F (+28 C) (Jupiter)

The above rough (at the telescope) sketch of Jupiter has North up and Preceding to the left.

Due to poor seeing conditions small-scale, moving "ripples" were constantly visible around the limb of the planet. The "star" to the upper right of the planet is Io, one of Jupiter's moons. A little later in the evening Io was seen in transit across the planet's disk. The following limb of the planet was slightly darker than the preceding limb due to the sun angle (a slight phase effect). At times more detail was visible; but under the circumstances (poor seeing and a relatively quick observation and sketch) some of the details shown may not be particularly accurate.

The planet's North Equatorial Belt (the darkest belt on the planet) appeared brownish-red in color. Other features had colors that were too subtle to differentiate from shades of gray.



After completing the Jupiter observation I observed and sketched Lamda Ophiuchi A&B, a close double star. The above sketch (greatly enlarged from the telescopic view) shows this double with North up and West to the left. A #82A Light Blue filter sharpened the view a bit under the relatively poor seeing conditions. The "A" star appeared to have a yellow or yellow-orange color while the "B" component appeared bluish. A narrow gap was visible between the two stars during intervals of somewhat improved seeing conditions. A weak, broken, diffraction ring was also visible at times around the two stars. A magnification of 218x was used for this observation.

Venus - 13 July 2007

Date: 13 July 2007 U.T.

Time: 2:50 U.T.

Telescope: 80mm f/5 achromat

Magnification: 85x

Filter: #56 Light-Green

Seeing: Fair

NELM: Bright Twilight

Temperature: +80 F (+27 C)

The above (mirror-reversed) sketch has North up and Preceding to the left. It shows the basic appearance of Venus as seen in a small telescope.

As the planet's phase changes from full to quarter (half) to crescent to new the planet's disk appears larger and larger. When Venus's phase is near full the planet is on the far side of the Sun. When the planet is a crescent it's on the near side of the Sun. These changes have a dramatic effect on the apparent size of the planet as seen in a telescope.

Currently Venus is moving closer to Earth as it orbits the Sun. As a result it's appearing increasingly larger as seen in a telescope and its phase is becoming a thinner crescent.

Venus is currently visible in the evening sky in the west immediately following sunset. It's by far the brightest object in that area of sky and readily visible to the unaided eye.

Comet LINEAR - 12 July 2007

Date: 12 July 2007 U.T.

Time: 6:32 U.T.

Telescope: 30cm Newtonian

Magnification: 90x

Seeing: Fair

NELM: 6.5

Temperature: +58 F (+14 C)

After the previous night's look at C/2006VZ13 LINEAR with binoculars I decided to have a go at it with a telescope.

In the above sketch South is up and West is to the left. I experimented with magnifications from 60x to 120x before settling on 90x as my preferred magnification for this comet. I worked on the sketch for 20 minutes while observing the comet; but the comet's position was "frozen" (in relation to the stars) at 6:32 U.T.

For those unfamiliar with comets, the stars in the vicinity of the comet in the above sketch are different from those seen on the previous night's sketch. This is because comets are solar system objects that are moving in orbits around our central star (the Sun). They appear to slowly move against the background stars. It can take seconds, minutes, or hours before one notices the motion - depending on the comet, its distance from the Earth and Sun, and the solar system geometry of the line of sight.

This particular comet looks pretty much like a "generic" telescopic comet. There's no easily visible tail. The comet simply looks like a circular, fuzzy, disk of light with a brighter central region. This is what most telescopic (and binocular) comets look like.

Comet C/2006 VZ13 (LINEAR) & Aurora

Date: 11 July 2007 U.T.
Time: 5:50 U.T.
Instrument: 20x80 Binoculars
Seeing: Steady (for binoculars)
NELM: 6.5
Temperature: +55 F (+13 C)


The above sketch shows the basic appearance of Comet C/2006 VZ13 LINEAR as seen with hand-held 20x80 binoculars. Only a few of the many visible field stars appear in this sketch. South is up. West is to the left. The comet is the large, round, nebulous object with a brighter middle. The galaxy, NGC 6015 was visible in the 20x80 binoculars as a much smaller and fainter nebulous object to the west of the comet. The comet was easily visible with 8x42 binoculars as well as with the 20x80s.

The comet was in the constellation Draco. Its rough location at the time of this observation was RA 15hr 57min, Dec. +62 degrees 28min. I estimated the comet's coma to be about 0.2 degrees in diameter. The comet is currently well placed in the evening sky for observers at mid-northern latitudes.

An aurora was visible a few degrees above my northern horizon. The aurora was somewhat brighter (with a small amount of structure visible) around 5:20 U.T. than it was at the time of the comet observation (5:50 U.T.). The aurora never extended very much above my northern horizon and seemed to have little or no effect on the limiting magnitude higher in the sky.