Friday, February 17, 2012

Winter objects from home

The weather as of late has not been conducive to stargazing, but a few windows did open in the rainy, cloudy and sometimes cold winter weather that is the norm for the Gulf Coast. During these periods I simply roll my telescopes into the driveway and observe what I can, despite the light pollution in my city. While that means most galaxies are impossible to observe, I can see a surprising number of star clusters, planetary nebulae and most of the Messier objects. The moon, planets and double stars do not require dark skies to see well. When the moon is up, I concentrate more on them than on deep sky objects. I was planning to observe from the airstrip last weekend but high winds and generally feeling unwell made going there not worth the effort to brave the cold. However, I did acquire an ultra-wide angle 24mm eyepiece for deep sky objects that have a large apparent size and had the opportunity to try it on some of the sky's most spectacular sights. Then I was in a position to see a rare conjunction of two planets where they approached each other closely enough to see both of them through a medium power eyepiece at the same time. Along the way I observed and sketched objects I've either never seen before nor sketched since the last time I observed them.
Two of my favorite objects are the nebulae M-42 and M-42, both of which are known as the Orion nebula. Even from a light polluted driveway they are wonderful objects, especially when a narrow band or O-III nebula filter is used. They and the star clusters flanking them provided a splendid opportunity to try my new 24mm Explore Scientific 82 degree eyepiece. Through the 10-inch, it gave a magnification of 55X and a true field of view about 1.5 degrees across, which is nearly enough to show the whole Sword of Orion in once view. The bright inner region of M-42 and the multiple star known as the Trapezium were of course prominently displayed but the two "wings" of M-42 were also clearly visible. Much of the rest of the nebula appeared as a faint glow that covered an area larger than the full moon. Through the 15-inch with an 18mm eyepiece and a narrow band nebula filter the nebula filled the field. M-43's comma like shape became apparent, along with the streakyness and patchiness of M-42 itself. The dark region known as the Shark's Mouth looked inky black compared to the emission nebulosity all around it. The open star clusters NGC-1981 and NGC-1980 which flank the nebulae were nice objects in their own right, but unfortunately it was not possible to see the reflection nebulae that pervade the region due to the light pollution.
When I was not looking at M-42 with my new 24mm ultra-wide angle eyepiece, I was trying it out on other large objects such as the Double Cluster, the Andromeda Galaxy, M-81 and M-82 and the Messier open clusters M-35, 36, 37 and 38. In every case stars will pinpoints to the edge, thanks to it's excellent correction and the use of a coma corrector. I cannot look through it without my eyeglasses, but that turned out to be uneccessary since when I look straight into the eyepiece stars turned into pinpoints to the edge. The Double Cluster fit into the field of view through the 15-inch with plenty of space to spare, and through the 10-inch open clusters such as the after mentioned  Messier objects were magnificent. Star colors were clearly apparent and the sky background was almost velvet black, evidently flare is almost non-existent and contrast is very high. When looking at M-38 through the 10-inch, the little open cluster NGC-1907 which lies next to the larger cluster was also clearly visible.
While looking at the Orion Nebula, I paid a visit to open cluster NGC-1981, which is overshadowed by it's neighbor.  This large and scattered open cluster is comprised of relatively few bright, blue-white stars and a lot of fainter ones, while being involved in the outskirts of the reflection and emission nebulae NGC-1973, 1975 and 1977. These are actually fairly easy to see from a good site away from heavy light pollution. This is a nice open cluster for all telescopes.
Aside from the three rich, large and bright Messier open clusters, Auriga also has a number of dimmer but still worthy of a look open clusters such as NGC-2126 in the northern reaches of the constellation. It's conveniently next to a bright field star, without which would make this cluster hard to find because the individual stars are quite faint. It appears as a wedge shaped area with more stars than the surrounding sky from my driveway. Doubtlessly it would be hard to miss from a darker area with a modest telescope given that it is a rich but dim star cluster. Evidently this 10th magnitude open cluster is not related to the 7th magnitude star next to is.
Another open cluster I located was NGC-2396, which is made up of some three dozen stars and shines with a total magnitude of 7.4. Not one of the richer open clusters, it took some effort to distinguish it from the dense star fields of Puppis, which lies along the winter Milky Way. One yellow star was brighter than the rest, and an even brighter field star was a signpost that lead me to this lesser known Puppis open cluster. Puppis
The open cluster NGC-2439 on the other hand was smaller but brighter than NGC-2396 with an apparent magnitude of 6.9, with a bright yellow star in it, almost like a topaz surrounded by diamonds. This cluster was very apparent even at low power, but it's fairly small size benefits from raising the magnification to about 150X. I couldn't make out all the stars, but in photos the cluster's brightest star are arranged in a ring, with the bright star as the diamond. The bright star is also listed as R Puppis, one of Puppis's many variable stars. This object is a good object for small telescopes and people observing from the suburbs.
Trumpler-9 is one of the more than three hundred open clusters listed by the American astronomer Robert Trumpler. Many of them were actual newly discovered objects while the rest were listed in other catalogs. Trumpler 9 despite it's appearing to be an asterism is a true open cluster, albeit one at a great distance from Earth. It was immediately recognized at 120X, and using an 8.8mm Explore Scientific eyepiece to boost the magnification to 149X provided a better view. While known as the "Greater than 1" cluster, my 10-inch brought in other stars that made it resemble the number 12 spelled out in stars. Small in apparent size, it is an object well suited to suburban stargazers.
The weather has been dismal for the most part this month for observing deep sky objects, but a rare event came along that does not require crystal clear skies. On the night of February 9th, Uranus and Venus passed some 20 arc-minutes from each other, making the pair fit nicely into any telescope's field of view. Although I was watching the event despite worsening passing clouds, I was able to make out both planets before it became fully dark. Venus showed it's yellow white color and darkening along the terminator, while Uranus looked like an aquamarine green pea some four times smaller in apparent size.

Among other things I have been observing Jupiter and Mars, which is soon going to reach opposition . Surface features are plainly visible when the seeing is steady enough to see them. I have also been paying more attention to Venus as well, given that faint markings do from time to time appear in it's thick, toxic and deadly clouds of sulfuric acid and molten sulphur droplets. Jupiter has also been displaying activity in it's atmosphere as well, there seems to be whitish regions lagging behind the Great White Spot. I had another opportunity to track down more winter deep sky objects from home this week sketches of which will be posted soon.

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