Last night, several SBAS members gathered at the Worley Observatory to observe the close-passing comet, C/2016 BA-14 PANSTARRS. Many astronomers, amateur and professional have been anxious about how bright C/2016 BA-14 will get. Estimates kept this comet at around magnitude +15 up until the last day or two from what I have read. Last night was a good first opportunity to photograph the comet despite a broadly encroaching 98 percent illuminated moon. The comet has been moving awfully fast through Cancer and will be in Ursa Major within days.
Of course, I am a visual observer, so in my case, anything dimmer than magnitude +13 under moonlit skies is out of bounds. I went to hunt for the comet anyway. My gamble paid off and I am three comets away from finishing the Silver Level of the Astronomical League’s Comet Observing Program.
Armed with Skysafari and my new red-light-friendly iPhone case, my XT8, and a dew shield to help cut out stray moonlight entering my scope’s tube, I starhopped from the head of Leo over into Cancer near Xi and Omicron Cancri where BA-14 was zooming through. I started with the 35mm Astro Tech and jumped down to 70x with my 17mm Plossl, but that still did not yield any results. Initial attempts at 150x in my 8mm TMB revealed nothing, but as the sky grew darker, I convinced myself something was there. A fellow club member brought over his new Meade 6.5mm 60HD which made my efforts a little less arduous. Something was there.
It appeared as a smudge at first, but with additional dark adaptation and cupped hands over the eyepiece to block out the moonlight, the smudge became more spindle shaped. The smudge, to me, resembled a magnitude +13 edge-on elliptical galaxy. To verify that it was the comet and not my imagination, I had to observe movement across the field. Luckily, BA-14 was moving in matters of minutes.
I had the right field according to Skysafari and BA-14 was headed toward a dim star, TYC-1404-1261-1. I sketched this observation at 9pm. At 9:03, the comet had moved more northward from TYC-1404-1261-1, half-way between that star and SAO-98369. Same elliptical shape. Same brightness. Averted vision and scope nudges helped, but there were moments of direct observation where the spindle shape seemed more apparent. I sketched this observation, but continued to follow its movement some more because I still doubted what I had seen.
When BA-14 passed SAO-98369, it seemed to get slightly brighter. Another club member had a look through my scope and confirmed that “something” was indeed there, so it wasn’t just my imagination. No core or condensation. No tail.
In terms of magnitude, I am convinced BA-14 was between +11 and +13 under the impression that +13 was nowhere near possible to observe under moonlit skies and my experience with observing +11 and +12 galaxies under home skies. Why it appeared spindle shaped still perplexes me because I logged a second set of observations when I arrived home.
BA-14 had moved closer to zenith by the time I arrived home and this particular location offered the added benefit of shadows cast by trees. I set up the XT8 under a shadow for the sake of better dark adaptation and protection from moonlight, looked up BA-14 in Skysafari again, and starhopped my way there. As before, the initial observation was extremely difficult, but “something” was there. This time, it was more round, so clearly being closer to zenith (74 degrees altitude) meant less gunk was between my eyes and the comet.
That is where things got interesting. When BA-14 moved toward magnitude 11 star HIP 45137, it brightened just as it did near SAO-98369. I observed a more round object instead of a spindle and the strain on my eyes was significantly less.
I don’t know much about these kinds of observations and those of you who like double stars, asteroid occultations, and other interacting/overlapping objects may have feedback on what I observed. I have two explanations which might make my observations make sense. The first is that since BA-14 is within our own solar system, background objects like stars emit light toward us and passes through anything between here and there…like a comet. Ideally speaking, one would probably observe a dimming of the background star as the comet passes in front as with any occultation, but it seems that it might also be possible that the star light may pass through the dust. My second and more likely explanation has to do with our eyes and vision. When our eyes focus on dim stars in the eyepiece, averted vision and dark adaptation work hand in hand, allowing nearby dim objects pop out much easier than when observed directly. Whatever the reason, my observations were logged and one more comet has been knocked out as I attempt to complete the first tier of the Astronomical League’s Comet Program.
I’m awaiting astrophotography shot by a fellow SBAS member to really compare my observations with what can be captured with more sensitive equipment.
Comet 252P/LINEAR is next on my list. It’s worth noting that astronomers think BA-14 is a piece of 252P.