Tuesday, May 10, 2011

Spring and summer objects from home

Last weekend I opted to roll out the 15-inch telescope and use it on the driveway to look at some bright deep sky objects visible from home, and sketch some of them. Sky conditions were however quite murky compared to last Friday night, where the skies were considerably clearer. That and the heavy dew scattered more light pollution which made even the likes of M-4 and M-22 look fainter than normal from my brightly lit up driveway. The moon was also in the picture, which I looked at along with the planet Saturn too.
Unlike the planet Saturn, I find even the crescent moon to be almost too bright to look at through a large telescope without eyestrain. 
M5 is the only bright globular cluster in Serpens Cauda, just to the east of the constellation Virgo. It's one of the few deep sky objects that does not suffer greatly from the light pollution in my city, in fact it remains bright, densely packed with stars and detailed from my front yard in my smaller telescopes. Through the 15-inch stars are visibly resolved right to the center, which shows itself as a intense mass of brilliant light.
This object is a magnificent sight through any good telescope, especially one that is at least four or five inches  in aperture.  I look at it time and time again.

M-62 is another bright globular cluster with an interesting personality, it's distinctly lopsided with the inner  core seemingly displaced from the center of the cluster. The apparent lopsidedness is apparently the star cluster's true structure, because M-62 is very near the Milky Way's nuclear bulge, whose gravity is tugging hard at  M-62. At 250X, the cluster plainly shows its stars from my front yard and the odd lopsided position of its inner core.
M-53 unlike the other two is much smaller and fainter, and in fact it does suffer from the light pollution in my city. However, its core still breaks up into stars, without much of an apparent central concentration. At 250X, the cluster plainly shows its stars from my front yard, but it looks much larger and brighter from a darker site.
Small, round and very bright, NGC-2392, also known as the Eskimo Nebula is one of my favorite planetary nebulae.It shows up very well in  all of my telescopes from the front yard, but through the 15-inch the inner shell is very distinct and ever shows the vaguely human face like outline. An O-III filter enhances the view tremendously, even from a dark site.
NGC-3115 is a compact and very bright galaxy in the constellation Sextans. Through the telescope it is very bright and has a lens shaped outline. While this lenticular galaxy is mostly a featureless collection of old yellow and red stars, some hints of structure do appear though the 15-inch. I spotted a dense inner core and hints of a band of stars along the galaxy's equatorial plane.
Before taking the telescope down for the night, I searched for and found NGC-6543, also known as the Cat's Eye Nebula. This planetary nebula can be seen easily in just about any telescope, but in smaller telescopes it looks like a very bright blue or turquoise oval that shows little or no structure and fleeting glimpses of the central star as well when the seeing is marginal or poor. The nebula stands up well to high magnifications, in fact the higher the magnification the better since the light of this object comes from a very small area of sky. Through the 15-inch, the central star was easily visible in spite of the mediocre seeing and hints of the whorls also appeared, something I never seen in this nebula even from a dark area with a 10-inch. No nebula filter at all was used when I made this drawing, but I plan to return to this nebula when I can look at it again from a dark area. There is a massive outer corona around the bright inner disk that should be visible from a very dark area with a nebula filter. NGC-6543 is therefore a triple shell planetary nebula, formed from repeated outbursts from the dying central star.

Normally a 15-inch truss-tube Dobsonian is used from dark areas. However, my experiences have shown, they can still be used quite successfully from a suburban area if one can get out the direct glare from streetlights and passing cars.