September 2018 LVAS Observer’s Challenge: NGC 6818 and NGC 6822

Report by ASSNE member Mike McCabe

The LVAS Observer’s Challenge object for September 2018 may have been the planetary nebula NGC 6818 in Sagittarius, but upon closer inspection of its exact location, it was clear that this challenge would be a “two-fer.” The very close proximity of NGC 6822, aka Barnard’s Galaxy, was impossible to ignore and simply had to go into the mix.

Research on the objects revealed that with 6818 I’d be looking for structure and color in the planetary nebula, but with 6822 I’d be lucky to merely confirm the existence of the galaxy. The planetary is bright enough to be seen in virtually any scope, but the galaxy exhibits a very low surface brightness that makes observing it a challenge no matter what scope you’re using. Regardless, NGC 6822 has such a colorful observational history that it practically begged to be included.

I was fortunate in this difficult stretch of poor observing weather along the US East Coast to get a few nights of clear skies near new moon time to work with. I also got lucky with the transparency and seeing on two of the three nights that I observed. Transparency ratings of 3/5 and seeing ratings of 3/5 would be considered above average for my area, and we consider those to be good nights indeed.

On the evening of September 1, 2018 I used my 80mm F7ED refractor and a 30mm/82* eyepiece to view the pair in a wide star field. I was decidedly applying the “less is more so maybe I’ll see this galaxy” approach, wherein you use low power to separate the low surface brightness object from the broader field of view. It didn’t work. I could never say on that evening that I caught a glimpse of NGC 6822.The planetary nebula was apparently non-stellar even at low power, and pushing the magnification up to 140x showed it as a fuzzy disc, but the small aperture limited the detail.

I was back out on September 3rd, this time using my 5” F9.3 refractor with the 30mm/82* eyepiece and the conditions were good enough to support a faint glimpse of Barnard’s Galaxy. The only way I could tell for sure was when I picked up on the orientation of it in the eyepiece. I was using an alt/az mount and in the field of view it appeared to slant with the bottom/east to top/west, which was of course reversed due to the diagonal mirror. It was a fleeting apparition at best, but that discernment felt like a confirmation to me. Soon after that observation, some clouds moved in and shut down my observing for the evening, and so with it any further study of the planetary for the night.

My final observations were made on September 4th, using my 10” F5 Newtonian reflector. Using the 30mm/82* eyepiece again, I was not able to repeat my success of the prior evening in seeing NGC 6822. The sky conditions were slightly worse than during my previous attempts, so I concentrated primarily on NGC 6818. Even though there is much knowledge about this nebula and it’s well known to be somewhat oval in nature, to my eye at 133x it appeared spherical and it also appeared evenly illuminated, so I wasn’t discerning any structure either. It did appear to hint at some color, which if pressed to say something I’d call bluish grey. The seeing wasn’t supporting any more magnification on this evening, and that ended my run with the Little Gem Nebula for this year.

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