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.



Friday, January 6, 2012

Winter deep sky objects

Last month some windows opened in the cloudy and rainy local weather that is the norm for December, which I put to good use to visit familiar and novel deep sky objects that are visible in the winter sky. Although I prefer to go to sites away from lights and passing vehicles, I frequently observe deep sky objects from my home despite the severe light pollution. Sometimes they show up surprisingly well through my 10 and 15-inch telescopes, sometimes I have to drive to a very dark area just to glimpse them through the 15-inch telescope. In any case there is always things to see regardless of where you're observing. Although I went to the airstrip to observe and sketch most of these objects, some were also observed and sketched at home.
NGC-1275 is the brightest member of a galaxy cluster in the constellation Perseus the hero some 300 million light years away from us. The other nearby galaxies NGC-1272, 1273 and 1276 are also members of this large galaxy cluster, most of whose members are elliptical and lenticular galaxies. All four of these objects are large elliptical galaxies devoid of massive blue stars. NGC-1275 is also a very strong radio source known as Perseus A, due to the presence of a super massive black hole in it's center feeding on gas, dust and stars that stray too close to it to escape. Visually it's merely an oval fuzzy object with a very bright inner core at 181X, which is billions of stars surrounding the black hole. Photographs show there is matter being ejected into space from the black hole and the galaxy is fairly similar to the nearby radio galaxy Centaurus A, another elliptical galaxy that is finishing off the last remnants of a spiral galaxy it recently merged with. In the surrounding sky I saw glimpses of other galaxies right at the edge of visibility all around this quartet of galaxies, but the seeing was poor and I wasn't able to use higher magnifications to pull them out from the sky glow.
The galaxy NGC-1404 in the constellation Fornax the furnace is normally an egg shaped elliptical galaxy, but recently the Type 1A supernova SN2011iv has appeared in it's halo. At 12th magnitude it's plainly visible and will remain so for some time before this exploded white dwarf fades from view. Also in the field is NGC-1399, another elliptical galaxy, both of which are bright with bright centers at 181X. These galaxies and about 16 others bright galaxies nearby are members of the small Fornax galaxy cluster, which is 60 million light years away. It's not well placed from my region of the country and is impossible to see from northern Europe, Asia and Canada due to the far southern declination, but farther south it's a rich hunting ground for those interested in observing galaxies of all types. It it possible to see 9 or 10 galaxies at a time here with a wide field eyepiece and a dark sky.
Fornax's compliment of deep sky objects is not limited to galaxies, it also contains the large and bright planetary nebula NGC-1360. This object is easy even in small telescopes to find and responds well to nebula filters too. From the southern U.S and Europe it is high in the sky enough to observe even with some light pollution present. Through a 6-inch NGC-1360 is a somewhat lopsided oval and through the 15-inch the central star is apparent. Strangely enough at 111X through the larger telescope the nebula is patchy and brighter along the ends. If you have a good view to the southern sky this is a great planetary nebula to observe.

Beyond the Fornax galaxy cluster there are other galaxies for modest telescopes such as the elliptical galaxy NGC-1395 in the constellation Eridanus the river. This 11th magnitude galaxy is small and bright, with a brighter core like most medium and large elliptical galaxies. This object is well within reach of a 6-inch or smaller telescope .
NGC-1385 is also an 11th magnitude object that is larger and is therefore fainter due to the lower surface brightness. This galaxy is an irregular or peculiar Sc type spiral galaxy whose spiral structure has a striking asymmetrical shape. Through the 15-inch I did not discern the spiral arms but did see a weak central brightening where the nuclear bulge was, and a somewhat irregular outline which does correspond to photos. A clearer night and better seeing would have allowed for higher magnifications, which would have helped show more structure in this galaxy, which undoubtedly was disturbed by a passing galaxy or a recent merger with another, smaller galaxy.
NGC-1371 is another Fornax galaxy that is bright and thus observable in small telescopes. This spiral galaxy shines at magnitude 10.8 and has a bright nuclear bulge. Like the Milky War it also is a barred-spiral galaxy with a weak central bar and a large disk, most of which was not evident but the portion I did see was subtly mottled or patchy, the first signs of it's spiral arms. No doubt higher magnifications and darker skies would reveal more of this fine spiral galaxy.
The bright open cluster M-38 is one of three wondrous open clusters in the constellation Auriga the Charioteer, but in the same low power field of view lies the overshadowed open cluster NGC-1907. This star cluster is an interesting object in it's own right though higher power eyepieces. Through the 15-inch at 227X, it looked very much like a star poor version of M-38. There were hints of numerous faint stars in the center. Overall, while not the equal of any of Auriga's big three Messier open clusters, it's an attractive and compact object that stands up well to light pollution and hazy skies.
NGC-7293 or the Helix nebula is one of my favorite objects. This planetary nebula is visible to large and small telescopes alike, but paradoxically it is also very faint despite it's apparent magnitude of 6. The reason for that is it's half the size of the full moon and therefore individual portions of it are very dim, but with a good  narrowband or O-III filter this object is visible from all but the most light polluted sites. At 142X through the 15-inch hints of the helices were visible despite the light pollution at the site. When the filter was removed, the central star became very noticeable but the nebula virtually disappeared. When the O-III filter was replaces the central star became very dim and the nebula became very distinct through the eyepiece. The best views to be had of this large wreath shaped planetary nebula is from very dark sites, but if you can get to any location where the sky is reasonably dark, this object is quite easy to observe thanks to nebula filters. This planetary nebula is probably the closest one to Earth, with a distance of about 450 light years.
NGC-2186 is one of many open clusters in Orion, though not nearly as well known as the Orion or Horsehead nebulas. This ninth magnitude object is scattered but surprisingly prominent from my home, although the rich starfields along the Milky Way makes finding the boundary of this cluster difficult. It's much better appreciated from a darker site than the suburbs of a larger city.
NGC-2196 is another open cluster located in the constellation Orion, but twice as large in apparent size as NGC-2186. It's a faiurly rich clump of moderately right stars and stood out better than it's apparent magnitude of 8.5 suggested from a bright urban location. Definitely worth another look from a darker site.
The open cluster NGC-2215 in the constellation Monoceros the Unicorn was the final object visited from my house with the 15-inch before I took down the telescope for the night. The star fields here are not as dense as the ones surrounding NGC-2186 and NGC-2194, and that made picking out the star cluster easier. It's apprent size and magnitude are similar to NGC-2194's, but it much easier to see as a distinct object. The arrangement of the brighter stars to me suggested the outline of an octopus, the cluster seemed to occupy most of the field of view despite the fact it's acutally much smaller than the moon in apparent size. Again, this open cluster seems worthy of a closer look from a darker site when the moon is absent.