Wednesday, April 30, 2014

Springtime galaxies

Last weekend saw the arrival of a reasonably good night, naturally I took the opportunity to look for some objects I wanted to see for the first time or get drawings of. So I drove out to the airstrip and set up the 15-inch while the sun was still up. After assembling the telescope and setting up the computer, it was time to collimate it and allow the cooling fan time to get the primary mirror closer to the falling ambient temperatures after sunset. Once it became dark enough to see some bright stars, I initialized the digital setting circles and the night's observing began. There was only about three and a half hours to observe under dark skies, because the waning gibbous moon rose just before midnight. So I concentrated on a few objects of interests in the constellations Lynx, Sextans and Pyxis.
NGC-2818 is an open cluster and planetary nebula in the southern constellation Pyxis with a planetary nebula appearing among its stars, like the Messier object M-46 in Puppis. While the open cluster was underwhelming through the murk near the southern horizon, the planetary nebula was easy to make out with an O-III nebula filter in place. It was fairly bright and large, looking somewhat apple core or barbell shaped. Shining at 8th magnitude and spanning nine arc-minutes, the star cluster is not particularly spectacular, but this planetary nebula would be impressive if it was higher in the sky from my location. It shines at a magnitude of 11.6 and is 35 arc-seconds across. I saw no other signs of structure or the central star that excites the nebula's gasses into fluorescing in visible light. To distinguish it from the star cluster, the planetary nebula often is referred to as NCC-2818A.

NGC-2537 is one of many galaxies in the northern constellation Lynx, which is now high in the skies after dark. This is an irregular dwarf galaxy that has peculiar bright patches in it that create the appearance of a bear paw, hence the nickname "Bear Paw Galaxy." It is also known as Arp-6 This object is an irregular system of type Sd, with a magnitude of 11.7. It's fairly small apparent size of 1.7 arc-minutes gives it a fairly high surface brightness. Also in the field can be found two other galaxies, one being NGG-2537A, a background galaxy at least 20 times further away than NGC-2537 in the foreground. The other is IC-2233, a faint edge on galaxy that eluded my 15-inch, probably because the skies were not very transparent that night. It lies 18 arc-minutes to the SE of NGC-2537 and forms a pair with NGC-2537A, which is unrelated to IC-2233. NGC-2537A was visible as a faint, round, fuzzy spot, which is all that can be seen of this very remote face on-spiral galaxy.

NGC-2549 is a lenticular galaxy of type SO also located in Lynx, but larger and brighter than NGC-2537. Shining at magnitude 11.2 and an apparent length of 4.2 arc-minutes, this galaxy has a relatively high surface brightness. This galaxy appears as an elongated object with a bright core, but is otherwise featureless because it's not forming new stars due to a lack of gas and dust. As a consequence, NGC-2549 mostly populated with older yellow and red stars.

In the inconspicuous constellation Sextans lies a number of galaxies modest telescopes can reveal under good skies. However, the murky and light polluted skies of my area demand a fairly large telescope to merely see many of these galaxies that are visible to smaller telescope at dark sites. NGC-3044 was however an interesting find that showed up quite well as the sky conditions worsened as the night progressed. Oriented south-southwest to north-northeast, this 12th magnitude edge-on galaxy appears as a slash of faint light some 5-arc minutes long. It was quite easy to make out at 142X. NGC-3044 is a SBc barred-spiral galaxy that resembles the Draco galaxy NGC-5907, but much smaller and fainter.
Another galaxy in Sextans worth a look is the face-on Sc type spiral NGC-3423. Small and round, this galaxy has a brighter center and spans some 3.8 arc-minutes of sky and has an overall magnitude of 11.2. This object bears magnification well, a point in it's favor because it is quite small as the drawing shows for a visual observer. I did not see any evidence of it's numerous H-II regions or it's spiral arms.
While at the airstrip, I brought along a red-filtered lap top computer which was helpful in locating these objects. I also tried out a shelter I made to keep the computer dry and warm enough to function properly, it was quite cool and very damp that night. Hazy skies and poor seeing were the order of the night, and the moon rising at midnight forced an end to observing deep sky objects for the night. I did get another look at the fading supernova in M-82, Mars and Saturn.; The seeing was certainly not the best for the planets, but with it being more often than not overcast locally, I take any chance I can get to look at them.


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