Observing Comets (and a few other things) from Joshua Tree, CA

by Jane Houston Jones

The rocks themselves were worth the drive. Molton liquid, heated by the movement of earth's crust, oozed upward and cooled while still below the surface millions of years ago. These intrusions of granitic rock developed a system of rectangular joints. Some oriented horizontally, some oriented vertically, and some overlayed the others at high angles. This system of joints developed rectangular blocks, and over millions of years water percolated down through the joint fractures, loosened mineral grains and rectangular stones weathered to spheres. Ancient flash floods washed away the ground surface and the huge boulders settled one on top of another creating the rockpiles we see today.

After an Octoberfest's-worth of beer and six varieties of sausages, red cabbage, onion bread and potato salad were consumed, we watched the shadow of the earth darken the valleys and eastern horizon, and prepared for a night of observing. First we held an old fashioned star party for about 20 friends and neighbors of our hosts. It was windy and the high clouds offered tantalizing sucker holes, which didn't dampen the enjoyment of the crowd, at least the crowd at our two sturdy Litebox reflectors. We offered views of Pluto, Uranus, some Milky Way wonders, and selections from the observing lists below for several hours until the guests drifted off homeward or conversation bound.

Hoping for an after midnight comet viewing clear sky, I took a disco nap and woke up at midnight to a clear windless night. The seeing wasn't great, but the sickly greenish glow of a neighbors mercury vapor spotlight had mercifully timed out. It was almost comet time!

While waiting for prime comet time, and continuing while Mojo was finding the comets in his 14.5 inch Litebox reflector, I hunted hopelessly for several fall Hickson galaxy clusters in my 17.5-inch reflector. The seeing wouldn't support the 200x magnification I needed for confirmation of these faint galaxies, although I may have seen a few galaxy blobs in amongst the star blobs. I'll try Hickson galaxy clusters 3, 4, 6, 9, 15 and 16 again next week at another Joshua Tree location - a location we discovered while completing a Messier Marathon with comet discover Don Machholz this past March 2004.

We first aimed our telescope at SN2004et, a type II supernova in mag. 8.9 NGC6946, a spiral galaxy in Cepheus, near the border with Cygnus. R.A. = 20h 35m 25.4s, Decl. = +60o 07' 17.6". The time of our observation was 1:45 a.m. 10/10/04 (08:45 UT) 10/10/04. NGC6946 was discovered in 1798 by William Herschel and eight supernovae have now been detected in this galaxy since 1917. It is leading the supernova statistics, with more supernovae more than follow-up galaxy M83 . SN2004et was discovered September 27, 2004 by Italian observer Stefano Moretti during a full moon.We used the AAVSO chart to find the supernova and also to estimate the magnitude. The chart, with its hand drawn galaxy spiral arms, also shows the location of SN1980. The supernova is located 4.1' E and 1.9' S of the galaxy nucleus, just west of a pair of mag 13.9 and 13.6 stars. Mojo estimated the magnitude to be 12.6 and I estimated it to be 12.9, using a nearby mag. 12.7 star and the fainter mag 13 stars for comparison. Try it for yourselves!

Then we settled in for some morning comet hunting.

First up Comet 88P/Howell. This comet was supposed to be mag. 13.37, coma diameter 1.5' R.A. = 02h 20m 48.3s, Decl. = +10o 06' 22" at 01:49 a.m. We looked for it at 1:55 a.m. (08:55 UT) and detected a small glow, more of a lumpy darkness kind of glow with averted vision. This was on the limit of the night's conditions.

2:10 a.m. (09:10 UT) Comet C/2004 Q2 (Machholz) Don's comet was a beauty! Congratulation to local California comet discoverer Don Machholz for his 10th comet! It should brighten over the next month or two! Right now, it's mag 9.14, and located in Eridanus. Coma diameter 3.7" R.A. = 05h 03m 26.1s, Decl. = -27o 34' 03" . We saw the bright nucleus and halo, but not much of a discernable tail. I tried it in my 17.5-incher, after Mojo located it in his 14.5 incher and I could at least see the direction of the tail with the additional aperture.

2:24 a.m. (09:24 UT) Comet 78/P Gehrels mag 11.67, coma diameter 2.8' near the Pleiades and Aldebaran in the morning sky. Smaller than Q2 Machholz, this comet had a more visible tail.

Our fourth and last comet was the most fun observation of the evening, following on the celebratory nature of observing Q2 Machholz. C/2004 Q1(Tucker) is a mag 11.5 comet we observed at 2:33 a.m. (09:33), coma diameter 1.7' comet located R.A. = 01h 48m 52.5s, Decl. = +21o 55' 09". The comet was easily seen, but the additional treat was spotting two galaxies in the same field of view. NGC678 and NGC680, a pair of nearly edge-on spiral and elipitcal galaxies that were an interesting find themselves! NGC 678 was a sliver of light which glows at 12.2 magnitude. Nearby NGC 680 is slightly brighter, 11.9 mag. and being eliptical, was nearly the same size (but a little larger) that the comet. A small nudge of the eyepiece would have revealed 5 additional galaxies in the 13-14 magnitude range had the seeing been better.

The wind had picked up, and the temperature was decreasing. Moonrise was at 3:12 a.m. but it took an additional 10 minutes for the 26 day old waning crescent to rise over the nearby Copper Mountain. First we saw the two "horns" appear, and soon the earthshine was cradled in a sliver of moon like a smile. We packed up the telescopes, and enjoyed sleeping in our friend's trailer for a few hours before heading for home two hours away.

Scary Halloween observing list: http://ephemeris.sjaa.net/0110/b.html

Caroline Herschel objects: http://www.seds.org/messier/xtra/similar/cher.html

Supernova 2004et http://www.astrosurf.com/snweb2/2004/04et/04etHome.htm

AAVSO chart for SN2004et: http://www.aavso.org/cgi-bin/shrinkwrap.pl?path=/charts/CEP/NGC_6946/NGC6946-E.GIF

Limiting magnitude charts: http://nineplanets.org/lm/rjm.html

Don Machholz's 8/27/2004 comet discovery: http://ephemeris.sjaa.net/0410/b.html

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Posted on shallow-sky Oct 11, 2004 21:56:17 PT
Converted by report.pm 1.2 Jan 14, 2005 19:38:27 PT