Saturday, November 12, 2016

Observing at the airstrip and the 2016 Deep South Star Gaze

After returning home from the 2016 OkieTex Star Party, I observed yet more objects from the local club's darker site then attended the 2016 Deep South Star Gaze for two days and nights. There I observed numerous galaxies, some of which I haven't seen before with the 15-inch. Objects that eluded my 10-inch appeared in the eyepiece when I brought the 15-inch to bear under the good skies that prevailed when I was there. The attendance was no where nearly as great as OkieTex, but over ninety people attended and the favorable weather ensured great views for everyone.
One object I observed in Cygnus many times is the emission nebula NGC-6888, also known as the Crescent Nebula. It is not a supernova remnant, nor is it a planetary nebula. In fact the nebula consists of the outer layers of a Wolf-Rayet star ejected into space by very strong stellar winds. Like O-type giants, these stars are blue white in color and very massive. However, the outward push of their radiation is greater than the inward pull of their own gravity, and that results in the outer hydrogen envelope being ejected into interstellar space while ultraviolet light from the fiercely hot surface ionizes the gasses. When atoms in that gas capture electrons, light is emitted as they drop to the ground state. The source of the nebula is the star offset from the center of the elongated oval outline, which shines at about 7th magnitude. In the next few hundred thousand years, that star will exhaust its remaining sources of energy and explode as a supernova. When the rapidly expanding debris catches up with the much more slowly expanding nebula, NGC-6888 will be dispersed and carried away from the site of the blast.
Cassiopeia is a rich hunting ground for open clusters, ranging from the Messier objects M-52 and M-103 to very faint open clusters that appear as faint blurs only even through large telescopes. NGC-103 is a fairly faint, small and crescent shaped swarm of faint and very faint stars that nevertheless stands out well against the surrounding star fields. NGC-103 is a faint object at magnitude 9.8, but it's fairly small apparent size of 5 arc-minutes made it bright enough to see through modest telescopes. A 15-inch and very dark skies are not needed to see this old open cluster. The darker skies at the 2016 Deep South Star Gaze certainly didn't hurt however.
Pisces is home to numerous galaxies, most of them faint. However, there's no lack of interesting galaxies, pairs of galaxies and even groups of galaxies available to amateur astronomers with 8-inch and larger telescopes who can get to reasonably dark skies. NGC-125 and 128 are a pair of galaxies I found easily from the airstrip with the 15-inch, with NGC-128's unusual shape and bright core being unmistakable at 227X. NGC-125 is smaller, fainter and round, with a brighter core. Their small size results in both galaxies bearing magnification well, due to their apparent size and magnitude of 12.3 and 2-arcminutes versus 11.6 and 3.4 arc-minutes for NGC-125 and 128 respectively.

Nearby in Cetus is another pair of galaxies that was quite easy for the 15-inch at the airstrip. NGC-192 is a 13th magnitude barred spiral galaxy, while NGC-201 is a fainter face on spiral galaxy with a magnitude of 13.6. Two other much fainter and smaller galaxies also lie nearby, but they went unseen due to their very small apparent size and magnitudes of 13.6 and 13.7, which in the rather poor seeing made them invisible. NGC-192 itself is the brightest member of a galaxy group that includes NGG-NGC-201, NGC-197 and NGC-196 as members. I intend to revisit this field on a night with better seeing because with higher magnifications NGC-197 and NGC-196 will appear in the eyepiece.
NGC-193 and NGC-194 is another pair of Pisces galaxies that proved to be an easy mark for my 15-inch at the airstrip. Both are oval shaped with apparent magnitudes of 13 and 12.6 respectively, with apparent sizes of 1.4 and .5 arc-minutes. That gives them a reasonably high surface brightness that easily overcomes the light pollution prevailing at the airstrip.

At Deep South I turned the 15-inch on the pair of Pegasus galaxies NGC-7673 and 7677. NGC-7673 is a small nearly round galaxy with a bright core, while NGC-7677 is a barred spiral galaxy of which I was only able to see the central bar which resembles an edge-on galaxy. NGC-7677 has an apparent magnitude of 13.2 while NGC-7673 shines at 12.4. NGC-7673 is a peculiar Sc spiral galaxy while NGC-7677 is a SBc barred-spiral galaxy.

NGC-7671 is another Pegasus galaxy that I observed at Deep South with the 15-inch. This galaxy appeared as an oval object with a brighter core at 227X. With an apparent magnitude of 13.1, this galaxy also has a companion nearby that I did not see, NGC-7672 which lies at right angles to NGC-7671. That much smaller and fainter system has an apparent magnitude of 13.8 and a very tiny apparent size of 1.2 arc-minutes. Quite possibly I missed it because of the fairly poor seeing and not using higher magnifications. NGC-7671 has a Hubble classification of S0, which agrees well with its appearance through the eyepiece while NGC-7672 is a Sb spiral galaxy.

Another Pegasus galaxy observed at Deep South was the face-on barred spiral galaxy NGC-7741. This system clearly showed the central bar and core at 227X while the spiral arms appeared as a oval and faint halo around them. I missed this galaxy while searching for it with my 10-inch, but found it quickly with my 15-inch which is equipped with Sky Commander digital setting circles. This galaxy is four arc-minutes across and shines at magnitude 11.2 in our skies at a distance of 30-million light years. NGC-7741is a good example of a face-on barred spiral galaxy that shows hints of its structure through medium and large aperture amateur telescopes.

Pegasus is also home to the pair of fairly small but bright galaxies NGC-7752 and NGC-7753.
NGC-7753 has an apparent magnitude of 12.2 while smaller and fainter NGG-7753 shines at magnitude of 14. Both show brighter cores, and in photos one of NGC-7753's spiral arms is pointing to NGC-7752. NGC-7753 is a barred-spiral galaxy of type SBc and NGC-7752 is a lenticular galaxy of type S0. Both were surrounded by numerous faint field stars.
NGC-7800 is an elongated Pegasus galaxy that readily showed up through the 15-inch at Deep South at 227X. This galaxy is an irregular system that's 3.6 arc-minutes long in apparent size and shines at magnitude 12.7. Quite faint, it revealed itself as an elongated and somewhat patch object nestled among faint field stars. I have succeeded in finding this galaxy from the much more light polluted skies near my city than the skies available at the Deep South Star Gaze.
The 2016 Deep South Star Gaze was blessed with good weather and pleasant temperatures at night. I brought an awning to get out of the Sun during the daytime, and I also observed the Sun with my 90mm Maksutov-Cassegrain and a front aperture solar filter. Curiously, there were no sunspots at all visible on the Sun, and even a look through a dedicated solar telescope tuned to the red light emitted by ionized hydrogen showed nothing on the Sun either other than prominences along the limb and silhouetted against the disk. It did however get so wet at night that my telescope was soaked and that required me to dry it out for a couple of days before I could seal it up to keep my cats out of it. While at the airstrip before, one of the resident cats did try to get into the mirror box in search of a comfy place for a nap. I gently persuaded him that the mirror box is not the place for him to get his nap, and like all cats outdoors at night he was gray in the dark.

Tuesday, November 1, 2016

2016 OkieTex Star Party

 At long last I had the opportunity to put my 15-inch Dob to the ultimate test, observing deep sky objects from a truly dark site. With much anticipation, I awaited the 2016 OkieTex Star Party held annually at Kenton Oklahoma. With an altitude of nearly 4,500 feet above sea level at the site, no large cities within 200 miles and a semi-desert climate, Camp Billy Joe is an ideal place to see galaxies and other faint objects with telescopes large and small. Below is a view of the site from one of the mesas that surround the site on three sides.
The site itself is owned by a group of churches who use it as a rural "retreat." As such it has parking, a dining hall and chapel, bunk houses and other amenities.
All around the site are mesas, valleys and little else other than ranches. In the distance is Black Mesa, so named because 30 million years ago the upper layers of rock were once vast floods of basaltic lavas. They hardened into dark brown rock that from a distance appears nearly black at the top of many mesas in the region, not just Black Mesa.
While approaching the site, I drove through stretches of nearly featureless land that was covered with grass and cactus as far as the eye can see. Aside from the wind, it is totally silent on these windswept grasslands.
The night skies were of course very dark. No large cities exist within 200 miles in any direction from the site, and the nearest towns are 40 miles or more away. No artificial lights were visible at all from the observing field except for red LED flashlights and red filtered computer screens. The image here I took with my Nikon 35mm SLR as I was observing with a time exposure about 45 minutes long with an wide angle lens. The silhouette of my larger telescope is visible at left, the red streaks are red LED lights used by myself and others to see objects in the darkness without totally ruining our night vision. I used a film camera to take all of the color images seen here. There would be no way I could have taken star trail photos like this one at home, the bright skies would fog my film in five minutes and I would have to use dew heaters on my camera and lenses to prevent dew from ruining my pictures. The 4,500 foot altitude and proximity to the Rocky Mountains ensured clean, clear air with moderate temperatures even at night. It was however rather windy, and on one night I was glad I brought the warm clothing.

Most people who came to the OkieTex Star Party opted to camp on site in tents, or came in a motor home. Others stayed in campers. I opted to stay in one of the bunk houses, three of which are pictured here. They were comfortable enough and I appreciated not having to sleep on the cold ground. Advancing age and cold often make the idea of sleeping on cold ground un-attractive to me. There were places where one could take a shower on site and eat a hot meal as well. That is very helpful given the nearest town is 40 miles away.
Pictured here is the observing field looking to the west. To the left are my telescopes, awning and a Chevy Traverse I rented for the trip. In western Oklahoma, the heat of the Sun is intense in September, which makes bringing an awning well worth the effort.

Sunlight illuminates a natural amphitheater atop a mesa to the south of Camp Billy Joe. The streak is the contrail from a passing airplane.

Geological wonders abound in the surrounding area, such as these pinnacles made of sandstone atop the mesa on the south side of Camp Billy Joe. They formed through erosion from the action of wind and water over long periods of time.
The area where OkieTex is held can best be described as semi-desert or high plains. No large trees exist except along water courses. What can best be described as scrub is found everywhere else, along with at least two species of cactus, grasses and other flora suited to the dry climate. Seen here is the access road to the site. Wild animals are also abundant, I saw numerous song birds, hawks and even a road runner. Deer, javelina and antelope also roam the area, and so do coyotes and mountain lions.
Mesas and buttes abound in the area, and some are open to hikers and other sightseers.
While large truss-tube Dobsonians were in evidence, many folks brought refractors and various kinds of Cassegrain telescopes too.
Telescopes of almost every size and configuration were well represented at OkieTex. including this 20-inch Corrected Dall-Kirkham Cassegrain telescope in the foreground on a fork equatorial mounting.
Large and huge truss-tube Dobsonians were commonplace at OkieTex, where dark skies enable them to show an observer objects very few humans have every seen with their own eyes. During the day, most were covered to protect them from the Sun's heat, dust and the possibility of sudden thunderstorms. I saw at least one there that was at least 30-inches in aperture. Mostly I looked through my own telescopes, but on the last night I took a look at a few objects through a 22-inch Dob. The much greater light grasp showed more galaxies in the middle of the Perseus galaxy cluster surrounding NGC-1275 than my 15-inch could, but it was also too large for me to even get into my car let alone my house.
The last rays of the setting sun washes across the mesas and valleys surrounding the site after sunset as observers ready their telescopes and cameras for another night of observing or imaging.

Barnard 142 and 143 are dark nebulae which appear as an inky black E shaped cloud in front of the Milky Way's background star clouds in Aquila. Also known as "Barnard's E," under the dark skies of western Oklahoma it was startlingly apparent even through the 11X56mm binoculars I bought at OkieTex. Through the 10-inch it showed its signature outline and variations in opacity across it's bulk. I used a 30mm Explore Scientific 30mm 82 degree eyepiece yielded a magnification of 44X and a true field nearly 1.9 degrees across which framed Barnard's "E" perfectly.
 It's either very hard to make out or impossible to see from my area due to the hazy skies and light pollution. Under truly dark skies this object is magnificent  even through binoculars and easy to find just to the west of the bright star Tarazed or Gamma Aquilae.

Abell 70 is a round, ring shaped planetary nebula in eastern Aquila. Small and faint, it is a very difficult object for the 15-inch at home, but was fairly easy to see from a truly dark site. An Orion O-III filter greatly enhanced this object, however the background galaxy that is directly behind the rim of the nebula I didn't not find. There was a slightly brighter spot along the rim but nothing obvious. The seeing at the time was not very good either, and stars were fuzz balls at 227X. Perhaps the next time I look at this object under dark skies when the seeing's good the background galaxy will appear.

Another planetary nebula I spent time observing was Minkowsky-1-79, located in Cygnus. At 227X through the O-III nebula filter this oval planetary nebula showed irregularities in its structure as well as a dark zone in the center. No sign of the central star appeared even thought he seeing was average to good.

M-45 or the Pleiades has always been one of my favorite objects. I have looked at it through binoculars and telescopes for over 40 years now, but only on a few occasions have I ever seen unambiguously the nebulosity that surrounds its bright stars. Once again my 10-inch and 30mm Explore Scientific 82 degree eyepiece provided the best view, allowing plenty of space to spare around the central concentration of M-45. At a distance of 400 light years, that central region is some 7 or 8 light years across. The nebulosity is mostly interstellar dust, which reflects light from the stars to Earth. Whatever hydrogen and helium that is present is not being excited into glowing because none of the stars in the Pleiades are hot enough to emit UV light energetic enough to ionize the gasses in the nebulosity. The clouds of gas and dust we see are not the remnants of the birth of the Pleiades, they are actually the subject of a chance encounter as the star cluster is passing through them at this time. Eventually, M-45 will leave the interstellar clouds behind, leaving them dark once again. Through my telescope, they appeared a lot like fog around street lights, and the nebulae surrounding the stars Merope and Maia has a silvery, streaky look to them. A look at the nearby Hyades and the fact the nebulosity was not symmetrical around the stars left no doubt I was really seeing the nebulosity and not fogging or dirt on my optics. This was the best view I had of the Pleiades in a long, long time.
Another object I observed was the nearby galaxy IC-10, which lies 2.2 million light years away from the Milky Way and some 600,000 light years from the Andromeda Galaxy which is also known as M-31. That makes it a probable satellite to Andromeda and a member of the Local Group of galaxies of which our galaxy is one of two dominant members. Most of the other members orbit M-31 or the Milky Way. The rest are scattered through the Local Group as isolated and independent galaxies. Through the 15-inch it appeared as an irregular, patchy, rectangular glow with a brighter region that is it's largest H-II region. H-II regions mark where star formation is underway, and IC-10 is also the only "starburst" galaxy in the Local Group. It's challenging to see when skies are hazy and light polluted, but for larger telescopes it's an easy catch under dark skies.
While the Andromeda Galaxy is the most well known galaxy in Andromeda, there's many others far beyond it. One of them is the distant galaxy NGC-562, a face-on spiral system that is at least 450 million light years away. It's so distant that it glimmers weakly at a magnitude of 13.5, which is why it appeared as a somewhat oval fuzzy patch with a weak central brightening. In Andromeda are also numerous other very faint and distant galaxies that are equal to or greater than our galaxy in mass, size and luminosity that can be seen under dark skies with a 12-inch or larger telescope. As faint as this one was, it was immediately apparent when I pointed the telescope at its position. The round shape and weak central brightening made this galaxy resemble a remote, unresolved globular cluster.
In eastern Eridanus near the bright star Rigel or Beta Orionis can be found a trio of galaxies that is nearly hidden in the glare of a bright field star. NGC-1618, NGC-1622 and NGC-1625 are all elongated, oval galaxies with brighter cores. NGC-1618 is an SBb barred-spiral galaxy with an apparent magnitude of 12.7. NGC-1622 and 1625 are Sb and SBb spiral galaxies with magnitudes of 12.6 and 12.7 respectively, which accounts for their apparent faintness through the 15-inch. The galaxies and the bright field star that impedes their visibility are arranged in a formation that resembles a slice of pie or pizza placed on the firmament.
In Draco can be found every type of galaxy imaginable, including the galaxy duo NGC-5777 and UGC-9568. NGC-5777 is an edge on spiral galaxy of Hubble classification Sb with an apparent magnitude of 13.5. It's needle like profile was readily apparent despite the poor seeing and so was it's bright core. UGC-9568 is a small face on spiral that is much smaller and fainter, but still was easy noticed at 298X. Both form a nice pair for anyone with at least a 10-inch at a dark site.
In Serpens there's a number Milky Way objects for the amateur astronomer to peruse, but there's also galaxies available to amateur astronomers in range of modest telescope.  NGC-6027, also known as Seyfert's Sextet  is a group of four merging galaxies with a fifth much more distant system in the same line of sight. The sixth object is in fact not a galaxy, but a tidal tail torn out of one of the four merging galaxies. The combined magnitude of all five galaxies is 13.8 and the group actually lies 200 million light years away. The fifth galaxy NGC-6027d is a face on spiral galaxy at the staggering distance of more than 800 million light years. The seeing was poor when I made this sketch, henceforth I was only able to clearly make out NGC-6027, NGC-6027a and NGC-6027b while NGC-6027c, NGC-6027d and NGC-6027e were blurred together. I once had the opportunity to view this galaxy group under better seeing and higher magnification. I was able to make out clearly five of the six members, including NGC-6027d, which is the most distant object I have observed through my 15-inch. This is a challenging object that is well worth pursing if you have a 10-inch or larger telescope under dark skies. Unfortunately, it's soon going to be out of sight and will remain so until Serpens reappears in the morning sky.The photo below is a helpful guide when observing this very interesting group of interacting and merging galaxies.
NGC-6106 is a Sc spiral galaxy in Hercules with a magnitude of 12.4. This galaxy exhibits an oval outline and halo with a bright core, consistent with a Sc spiral that is inclined to out line of sight. This galaxy is fairly faint and thus is not going to be observable when skies are light polluted or flooded with moonlight.
Bright globular clusters abound in the summer skies, but faint and challenging to merely find are even more numerous. One such object is the Aquila globular cluster NGC-6749. Like Palomar 11 also in Aquila, NGC-6749 requires dark and clear skies and at least 8 or 10-inches of aperture to have a chance of spotting it. Shining at a magnitude of 12.4 but an apparent size of 5.2 arc-minutes, NGC-6749 is much fainter than its apparent magnitude suggests. All that was visible was a faint round spot of light with a weak central brightening. What makes this globular cluster so faint is not extreme distance from the Earth, it actually 25,800 light years away from us and some 16,000 light years from the galactic center. We are looking at this globular cluster through very dense clouds interstellar dust that blocks most of its light. Because of that, NGC-6749 is heavily reddened in color images due to absorption of blue light by interstellar dust.

Another faint globular that eluded me from home is the Ophiuchus globular cluster NGC-6366. Under western Oklahoma's dark skies, this and other objects I cannot see at all from home became easy objects for the 15-inch. Glowing at ninth magnitude, NGC-6366 displayed a loose structure through the 15-inch at 181X, with numerous faint stars resolved across its face. NGC-6366 is very close for a globular cluster at 11,400 light years, only a few are known to be closer to the Solar System. It's faintness is readily explained by it's low luminosity, and the considerable absorption by interstellar dust. NGC-6366 has an absolute magnitude of -5.7, considerably less than average for a Milky Way globular cluster which have absolute magnitudes of around -8 or more. The brighter Messier globular M-14 lies three degrees away to the northeast.

NGC-6384 is one of the relatively few galaxies in Ophiuchus that are moderately bright and therefore not just faint featureless blobs in the eyepiece. At least that is, if you have access to a medium or large aperture telescope. Strongly elongate with a bright nuclear region, NGC-6384 is obviously a spiral galaxy through the 15-inch at 227X. The disk seemed subtly patchy and this galaxy does show a well defines spiral structure in photos. NGC-6384 shines at a magnitude of 11.1, spans 6.2 arc minutes of sky and has a Hubble classification of SBc, which makes it similar in structure to our own galaxy. The system lies 60 million light years away. It's surface brightness is fairly low, which makes this galaxy one that should be saved for trips to dark sites.
The galaxy pair NGC-1 and 2 in Pegasus is another galaxy duo I visited while attending the 2016 OkieTex star party. These galaxies glow at magnitude 12.7 and 14, putting them out of reach if skies are light polluted or milky. They span 1.6 and 1 arc-minute, which gives them a surprisingly high surface brightness that made them easy to find. Both appeared as small, oval glows with NGC-1 showing a bright core while NGC-2 showed a weak central brightening.
On Friday morning it was time to take down the telescope and awning and pack them into the Chevy Traverse I rented for the trip. This is a fairly large Sport Utility Vehicle that held my 10 and 15-inch telescopes with plenty of space to spare for other items I needed to bring with me. Before it was time to leave and start the long journey back home. It took two days to drive to the star party and back home, a 1,300 mile or 2,100 kilometer journey each way. I had observed more than 200 objects with the telescopes and binoculars. With those I had seen dozens of objects ranging from dark nebulae to galaxies. An even larger number was observed through my 10 and 15-inch telescopes which revealed objects up to the limit of their capabilities. Attending the 2016 OkieTex Star Party was a wonderful experience I hope to repeat in the near future. The road to getting the 15-inch under some of the darkest skies to be found anywhere in North America was a long but ultimately rewarding one.