Clusters by the Light of the Moon

Observer: Tom Campbell
Location: Iola, Kansas (Long: 95°24'W Lat: 37°55'N)
Equipment: Discovery 8" DHQ dob
Time: 9:00pm - 10:30pm CDT (02:00-03:30 UT)
Transparency: Clear (8/10)
Seeing: Mostly Stable (7/10)
Weather: Temperatures in the lower 50s. There was little or no breeze.

Observing Summary:GEMINI: NGC2129, NGC2395, NGC2420
VIRGO: M104

I've been wanting to view a few Herschel open clusters in Gemini, but the weather and my schedule hasn't been cooperating. Tonight, the nearly First Quarter moon was in Gemini, but the sky was so clear, I decided to give it a try anyway.

NGC 2129 | Gemini | Open Cluster | 9:00pm CDT
| RA: 06h 00m 42s | Dec: +23° 19' | Mag: 6.7

This cluster contained two bright stars and several fainter ones. The brightest star had a slight yellowish color. The overall shape of the cluster reminded me of the letter D, and was best viewed at 122x. Most of the stars were along the border of the cluster.

NGC 2395 | Gemini | Open Cluster | 9:15pm CDT
| RA: 07h 27m 12s | Dec: +13° 37' | Mag: 8.0

The overall shape of this cluster was triangular, with faint stars scattered randomly throughout. Perhaps a dozen stars were seen with averted vision. Perhaps due to its faintness (or the brightness of the nearby Moon), this cluster was disappointing.

NGC 2420 | Gemini | Open Cluster | 9:30pm CDT
| RA: 07h 38m 24s | Dec: +21° 34' | Mag: 8.3

This cluster appeared rich, with several stars packed into a rather small area. I have added this to my list of things to observe when I have a darker sky. The shape was fairly circular.

M 104 | Virgo | Galaxy | 10:00pm CDT
Sombrero | RA: 12h 39m 59s | Dec: -11° 37' | Mag: 9.0

I saw Corvus peeking above the tree line, and decided that before I headed back inside, I'd take a look at M104. Tonight, I noticed on my star charts that there was a chain of bright stars leading from Gamma Corvi to M104, so I thought I'd try this new route of starhopping tonight. Sure enough, at low power, each star along this "Sombrero Highway" was just about one FOV away from each other. The last "star" in the chain was actually a Sagitta-shaped asterism which pointed right to the galaxy.

The galaxy's dust lane was very noticeable, as usual, but the seeing was getting worse so that the galactic core "below" the dust lane was only visible occasionally with averted vision. Regardless, this galaxy always impresses me. The best view tonight was 81x.

A few weeks ago, somebody on one of the Internet astronomy boards stated that he mounted an indoor/outdoor thermometer to his telescope, to determine when his mirror had cooled down sufficiently. I did the same thing, and it was fascinating. The seeing started out pretty decent, but worsened as the night wore on. Checking my thermometer, I noticed that the outdoor temperatures were dropping faster than my mirror was cooling. What started out as only a 2° temperature difference when I started had increased to about 6° when I finished up! Add to that the fact that the relative humidity (my thermometer shows that, too) had climbed to 76%, and it was little wonder that the seeing was getting worse.