Jan. 7, 2013 – My first encounter with Comet ISON

Comet C/2012 S1 ISON photographed on Jan. 8, 2013 in Gemini. John Chumack shows the comet’s brightness as 16.2; other estimates place it closer to 15.7. Credit: John Chumack

OK, it’s full name is C/2012 S1 (ISON) but honestly, I can’t squeeze that in a headline. Amateur astronomers have been photographing this much-anticipated comet since its discovery last September. All along, it’s been a tiny, faint object beyond the visual reach of most amateur telescopes. That’s because it’s so dang far away.

Jupiter, that big, bright “star” in the southeastern sky during early evening hours, is 400 million miles from Earth today. Comet ISON, a pipsqueak iceball 3-4 miles in diameter, lies 391 million miles away or nearly as far as the planet. It’s still too distant to show anything more than a bright center enveloped in a small, fuzzy coma. Come fall however, the comet is expected to blossom into a spectacle as it passes near the sun and sprouts a significant tail.

Who would even bother trying to see a minute bit of 15th magnitude fuzz? Well, there are two good reasons if you’ve got a large telescope. Small, compact things are much easier to see than large, extended objects of the same brightness. All the peanut butter comes in a little cup instead of spread thinly across the slice of bread.

Comet ISON moves through the field of view of my eyepiece on the night of Jan. 7-8, 2013. Faint stars are crucial guides to mark a comet’s movement. ISON was 15 arc seconds in diameter and traveling at the rate of  ~30 arc seconds (1/60 the diameter of the full moon) per hour at the time.  Very slow! Illustration: Bob King

Comet ISON also happens to be in the constellation Gemini, which rises high above the horizon haze into a dark sky by mid-evening. Since I felt my main telescope, a 15-inch reflector, was up to the task, and inky skies beckoned 25 minutes north of my home, what could I do but accept the challenge?

After chowing down on pizza, an important food group for amateur astronomers, and armed with a detailed star chart showing the comet’s location, I drove to a dark site and set up the telescope. Since it’s easy to convince oneself of seeing a faint object at the limit of vision, the only way to be sure it was the real thing was to employ the acid test. Would I see the comet move during the night?  If the same dim object marches along in the right direction at the right speed over a span of several hours, one can be confident of seeing it. Otherwise one’s strong desire to see a dim object can make it magically materialize when it’s not really there.

So how much time would it take to see ISON budge? Based on the nearby stars available to reference the comet’s motion and considering its great distance from Earth, I figured I could nail it in two hours. I peered into the eyepiece using of magnification of 257x at 9 p.m. High magnification darkens the sky, making faint objects easier to see, but it also blurs stars and planets compared to low power views because you’re magnifying swirling air currents in the atmosphere. Luckily, turbulence was low and within 5 minutes, I could just discern a small, very faint fuzzy spot with a brighter spot in its middle at the correct position.

I had to use averted or peripheral vision, a technique of looking around and about the comet instead of directly at it, in order to see it more clearly. Let’s be honest here – in order to see it at all.

Russian amateur astronomers Artyom Novichonok (left) and Vitali Nevski discovered their comet on Sept. 21, 2012.  Copyright: Artyom Novichonok

After tooling around in Taurus looking at an assortment of star clusters, I returned two hours later at 11 p.m. Aha! ISON had slid away from its 9 p.m. spot … but where to?

After 20 minutes of searching, I finally picked it up again. The comet had been “hiding” between two faint stars. The distraction from even their feeble light had made it almost impossible to see. Better wait another hour just to be sure. At midnight, ISON cleared the pair and was once again in plain view. Hurray! My first new comet of 2013.

Now to watch and wait. In the coming months, C/2012 S1 ISON will gradually brighten and change in wonderful ways. One of the astronomy’s joys is getting there early to see stuff before the big show begins. Kind of like a backstage pass or touring with the band. You might suffer sleep deprivation in either case, but feel a sense of satisfaction in learning the inside story.

I encourage anyone with a larger scope and dark sky to meet ISON’s acquaintance at the earliest opportunity.