Amateur astronomers have been busy the past few mornings with telescopes and cameras searching for what’s left of Comet Elenin. I’m aware of at least a half-dozen attempts to see the comet, all but one of which resulted in a negative or uncertain result. Leonid Elenin’s photograph posted in my Oct. 6 blog may possibly show a fragment of the comet.
This morning was the best opportunity to look because the comet was moderately high in the eastern sky (about 23 degrees or “two fists”) during a narrow window of darkness between moonset and twilight. Observing from a mountain location over one mile high near Leon in northern Spain, dedicated comet observer Juan Jose Gonzalez saw Elenin as a faint, diffuse haze of magnitude 10.7 with a short tail pointing northwest. The comet had no central brightening and measured 6 arc minutes across or half the distance between Mizar and its companion star Alcor in the Big Dipper. Gonzalez was using an 8-inch Schmidt-Cassegrain telescope, and seeing conditions were very good at the time.
His is the only positive observation so far. The news gave me a jolt of hope that I and others might still see it. Photographs and other attempts have either shown a tiny 18th magnitude object or a suspected faint patch of light. These earlier observations were made when the comet was lower in the sky and its light more readily absorbed by the thicker, hazier air near the horizon. Gonzalez is an expert observer working under very dark skies. He routinely sees faint comets that escape the attempts of other less experienced amateur astronomers, myself included.
Still, why the disparity between his and Leonid Elenin’s 18th magnitude estimate of the comet’s brightness? Two factors may be at play. Elenin’s was based not only on a photograph, but also when the comet was much lower in the sky. I don’t know the field of view of his photo, but if it’s small – and especially with the comet much lower – it might not show the distended, faint coma but rather a fragment inside. That fragment, if that’s what it is, is obviously very faint. Elenin is still not sure if what he photographed is the comet or just noise.
Meanwhile, Gonzalez observed the comet much higher up with a wider field of view. Although unable to see any fragments – they’re too faint to spot visually – his wider field of view, darker sky (due to higher elevation) and very perceptive eye allowed him to see the entire coma and even a short tail. Based on the details of his observation, the coma would have looked like the faintest puff of light just a little brighter than the sky background. Although 10.7 magnitude is not faint per se, that brightness is spread across 6 arc minutes of diffuse haze, making the comet appear quite dim. Having compared my observations with Gonzalez’s for a number of years now, I’m guessing it would have been very faint from my dark sky site even in my 15″ reflector. No one to my knowledge photographed the comet this morning with a wide-field telescope. Had they, we’d have a better basis for comparison.
Tomorrow morning (Oct. 10) offers one last opportunity to see the comet before moonlight cuts it to the quick. Since the nearly full moon will set about 15 minutes after the start of twilight, there will be no true darkness, but it may prove just dark enough for the comet to make a very brief appearance before dawn grows too bright. Take heed! Comet Elenin is dim and diffuse and will prove a challenge even for amateurs with larger telescopes and good maps. Use the map above to help you find it. The comet will be about 4 degrees northeast of Regulus.
After tomorrow, a bright moon will make it virtually impossible to see the comet until October 21, when Elenin will once again be sufficiently high in the east to tackle before moonrise. After the 21st, conditions rapidly improve – by the 24th the comet will be high in the southern sky before the start of morning twilight.
I realize that all this talk about such a dim comet may be overmuch for some of you reading this, but had Elenin not broken to pieces in August, it’s possible we’d be seeing it in binoculars by now. What’s visible now is the dim, expanding dust cloud from the vaporization of icy-dusty cometary fragments. Speaking of which, it sounds like the eastern hemisphere had a fine Draconid meteor shower last night. We were cloudy here in Duluth, Minn. For fun I built a bonfire in the backyard and watched a homemade meteor shower of orange sparks fly to the heavens.