Herschel 400 Objects

NGC 2362 "Tau Canis Major Cluster": Open Star Cluster (Canis Major) RA: 07h 18.7m / DEC: -24° 57'.3
Instrument: 10-inch Starfinder

This is quite simply one of the most striking star clusters in the winter sky. It is also among the most fascinating. Centered within the cluster, although not necessarily a member, is 4.4 magnitude Tau Canis Majoris. Hipparcos photometry revealed this wintry beacon to be not one but three stars. A visual double consists of two O-type stars separated by 0.151 arcsecond. The brightest member of this binary system is, itself, a massive binary with a period of just one day. Tau Canis Majoris is composed of the longest peroid spectroscopic binary and the shortest period eclipsing binary for known O-type stars.

My drawing presents NGC 2362 as viewed at 129X in the Starfinder. A crisp white beacon of light at the eyepiece of my 10-inch, Tau is surrounded by a host of fainter stars as shown in the sketch at left. Among these, is a closely formed trio of faint stars immediately east of Tau. Seven arc minutes due east, 6.8 magnitude HD 57192 stands sentry at the edge of the field. An equal distance to the west is 9.2 magnitude PPM 727417. In between, lie more than 60 stars huddled around Tau Canis Majoris. NGC 2362 is 6' in diameter, according to Archinal, so most of the stars in my sketch are members.

Instrument: 18-inch Obsession

Here's an interesting comparison observation made with the Obsession. The magnification is 199X and, as in the above sketch, Tau Canis Majoris is centered. The orientation is about the same but many more stars are visible. The 18-inch has more than 3-times the light-gathering power of the 10-inch, which translates to seeing stars more than a full magnitude fainter. My drawing shows about 100 stars buzzing around Tau Canis Majoris. Most are cluster members and all combine to form one of the most beautiful compositions in the celestial show.

NGC 2360 NGC 2371


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Revised: December 4, 2005 [WDF]