Monday, April 23, 2001

Backyard observing 4/23/01

I took out my 8" f/6.8 collapsible Dob ( last night for a short galaxy hunting session. I did not have very high expectations as a haze layer appeared to be in place, possibly brightening things up to the point of uselessness. However, once darkness set in I was out back and things seemed decent. There was some unsteadiness as brighter stars were twinkling. Temps were very pleasant, reminding me that summer is on approach. There was virtually no dew during the observing session.

I used two eyepieces, the 20 and 12 Nagler, both type II. Other tools were a Telrad, old version of SA2000, and Uranometria.

I began with NGC 2681 in Ursa Major. This galaxy is in a very easy location for naked-eye star hopping, sitting just above the toes of the Big Bears front upper paw. I used 25-Theta Ursae Majoris to draw a line to 15 Ursae Majoris, which pointed to the target's position. The galaxy was in the eyepiece immediately... a nice way to start an observing session. This is a bright galaxy at mag 10.3, but the surface brightness is significantly dimmer due to its 3.6' x 3.3' size. I thought there was a possible elongation to the galaxy in the WNW/ESE direction, but mostly round, with a stellar nucleus. A few bright stars sat nearby, one 10' N and another 12' S.

My next target was NGC 2683. This is a great object! Sitting in Lynx. The general position in easy, using the southern end of the dim constellation as a guide. The stars 40 Alpha Lynx (mag 3.1) and 38 Lynx (mag 3.8) allow you to form a right angle to their east. You find yourself in a rich starfield... it is fairly easy to know when you are there. A chain of three bright stars point toward the galaxy, framed on the opposite side by a pair of bright stars. In the 20 Nagler this galaxy, while rather dim, actually jumped out. There was no missing it. It is very elongated at 9.0' x 2.2' in a WSE/ENE orientation. Three dim stars sit to its south. I found it to be better at lower power, as it was very ghostly in the 12mm eyepiece. This one is a "must see" from the backyard... mag 9.8, but its surface brightness is a dim 12.9.

NGC 2742 is an object I've looked for previously in my backyard, but failed. The location is relatively easy, as it is at the intersection of two distinct "lines" described by bright stars in Ursa Major. 23 Ursae Majoris points through 16 Ursae Majoris and intersects the line made by 29 Upsilon Ursae Majoris and 1 Omicron Ursae Majoris. Nothing could be easier! However, with the 12mm Nagler, this galaxy was barely flitting in, just a faint "sometimes" glow about 3' W of the brightest star in the field. Perhaps conditions had deteriorated, making this a tough object. I could not detect much detail, although at times it appears elongated. This was one the toughest object of the night, mag 11.4 with a 13.0 surface brightness.

I finished my observing session on NGC 2768, located close by NGC 2742. In fact, I used the same bright star and double that pointed me to NGC 2742 in locating NGC 2768. This galaxy too was dim, but more visible than the prior one. It was elongated E/W and about 8' x 4' in size. With averted vision I could detect a stellar core. A very dim star sat close to the E side of the object. Two brighter stars sat 4' away, one to the N another to the WNW.

By now it was getting late. My scope was performing wonderfully, but I knew I had an early day the next morning.

I packed up my books and eyepieces, left the scope outside. It is there waiting for another observing session tonight.

No comments: