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.

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