Sunday, January 22, 2012

Wonders of the winter sky

This weekend clouds and rain ruled out driving out to the airstrip today with the telescopes, but the previous weekend was altogether different weather wise. Temperatures were fairly warm and surprisingly enough the dew was not nearly as bad as it usually is, soaking everything within a couple of hours after sunset. Sky conditions were average, good enough for the improvement in the views compared to what I see from home for the drive to the airstrip to be worth while. While there I tested an experimental red LED illuminated clipboard, the purpose of which is to make sketching objects at the telescope easier. Early results were encouraging but it is clear the clipboard should be powered by it's own internal battery instead of being powered by a cord plugged into one of my Dewbuster's accessory ports. The variable brightness feature I incorporated into it is very helpful to reduce the impact on my night vision, and the white LED's are bright enough to serve as illumination for setting up and taking down the telescope. Last weekend I mainly focused on the Eridanus, Lepus and Orion region, given the large number of galaxies and nebulae in this region of the sky.
The constellation Lepus the Hare has only Messier object, the modestly bright globular cluster M-79. Through small telescopes it looks like a comet unless skies are very dark and the magnification high, but from the light polluted skies at the airstrip M-79 readily resolved into stars. at 227X it shows a small but very bright core, with hundreds and hundreds of stars resolved in it's outer reaches. It's a fairly impressive object in medium and large aperture telescopes despite it's modest luminosity and distance of over 50,000 light years from Earth. Through the 15-inch it reminded me of a pinch of salt or sugar on very dark fabric.
The other prominent deep sky object in Lepus is much closer to home, and that is the planetary nebula IC-418. Also known as the Spirograph and Raspberry nebula, this tiny, bright planetary nebula is visible in both small and large telescopes as a small bluish oval disk with the central star prominently shining in the center. It has shown a reddish tint, hence the popular name Raspberry nebula. Despite the quite bad seeing that night, I boosted the magnification to 298X. As before the central star shone brightly in the middle of the nebula and the bluish color was evident. Interestingly the ends along the long axis seemed dimmer than the rest of the nebula. Like many other bright planetary nebulae, IC-418 also "blinks," looking directly at the central star caused the nebula to vanish, looking away brought the nebula back into view.
As the night wore on. I looked at a number of galaxies until moonrise washed them out. The first galaxy I looked at was the Eridanus galaxy NGC-1187, an oval shaped barred spiral galaxy that shines at 11th magnitude. The bright core was prominent, which was surrounded by the disk and spiral arms. I probably would have been able to see hints of the spiral structure at a darker sight on a calmer night, but this galaxy is clearly bright enough for a small telescope to reveal it. The disk steadily brightened towards the center however, and I plan to revisit this galaxy on a better night.
NGC-1232 is a 10th magnitude face on  Eridanus spiral galaxy very much like M-101 in Ursa Major, but almost three times farther way than the Pinwheel Galaxy. The poor seeing and light pollution hid the outer portions of the disk, which I was able to see easily from a much darker site through my 10-inch. The central region was easy to find and given a dark site this galaxy is a good object for medium and large aperture telescopes. There is a small companion galaxy that is perturbing the big spiral galaxy's arms, but I never seen any sign of it from the airstrip so far.
NGC-1309 is  a nearly face on Sc spiral galaxy in Eridanus that resembles the nearby spiral galaxy M-83 with it's oval shape due to it's orientation with respect to our line of sight. Shining at magnitude 11.6 and much smaller than the previous two galaxies in apparent size, it has less trouble getting through my area's sky glow. The bright nucleus is very evident and the galaxy looked a little patch as well at 181X. Bright and easy to locate by star hopping, this object begs a second look on a steadier night from a darker site than the airstrip.
NGC-1421 is an interesting Eridanus galaxy, starting with the fact it's an edge-on system. It is also somewhat irregular in structure. this system is also oriented due north to south as it softly shines at magnitude 11.6. Little structure seemed to appear, it looked like a streak or slash of faint light that at first was not immediately apparent at 181X.
Over in neighboring Eridanus the galaxy hunt continued with the rather small, faint and oval galaxy NGC-1784. Shining at magnitude 11.8, this barred spiral galaxy lies 100 million light years away, over half again as far away as the Virgo cluster of galaxies, and yet it was fairly bright through the 15-inch. It bore magnification quite well but the unsteady air above led to the best view being found at 181X. I saw no sign of the small companion galaxy near it, probably because it is either actually a much more distant background system or it's an intrinsically dim galaxy to begin with.
Another Eridanus galaxy that eluded me until now is NGC-2139, which shines at a magnitude of 11.7. It's small apparent size of just over 2 arc-minutes gives it a fairly high surface brightness and thus makes it visible fairly well amid the local sky glow. This face on Sc type spiral galaxy really does deserve to be also considered a peculiar galaxy. The central core is displaced to one side and photos show the spiral arms to be disheveled as well.
Just before the moon rose and forced an end to observation of deep sky objects, I stopped to visit M-78, a reflection nebula in Orion that is often overshadowed by the Great Orion Nebula. This object is a interesting object in it's own right  from a dark site. It's actually four separate small nebulae in the same region of sky. While M-78 resembled the eyes of some celestial black cat gleaming from within the nebulosity, NGC-2071 was a lopsided fuzzy patch around a star. NGC-2064 and NGC-2067 eluded me since the moon was already lighting up the sky as I made the sketch. Next time I'm going to return to this area and see if I can spot them, they have been seen in small telescopes from dark sites.

In addition to these objects I observed a number of others, which included Venus, Mars and Jupiter, which suffered the least from the night's poor seeing. I also looked at the galaxies M-31, M32, M-110, M-33, where in M-31 and M-33 I spotted the dust lanes and spiral arms respectively. I spent a good deal of time looking at the Orion and Crab nebulae, which shows many details through the 15-inch. Finally I looked at the galaxies M-81 and M-82, which looked incredible until the moon's glare began to hinder even them. It was a pleasant night of stargazing while the darkness lasted.

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