Archive for the ‘Nightwatch’ Category


Comets past and future

January 22, 2013

Wow, three months exactly since my last post. Between holiday travel, weather that has mostly been either cloudy and rainy or clear but bitterly cold, and staying busy with dinosaurs, I’ve only been out for a couple of quick peeks since the last post. But I’m still alive, and I’m sure I’ll get back to observing–and posting–when the weather gets better.

In the meantime, I’m recycling my president’s message from the November issue of the PVAA newsletter, Nightwatch. You can find all the back issues of Nightwatch online here.


I am not a dedicated comet-chaser. Every year, several short-period comets brighten to the point that they can be seen with binoculars or a small telescope, but I almost never track them down. In fact, I’ve only seen three comets in my time in amateur astronomy, but each one has left a big impression. And curiously, all three have been October arrivals.

The first was comet 17P/Holmes, which brightened to naked-eye visibility in late October, 2007. It was extremely good timing for me: I had just gotten my first telescope three weeks earlier. For months I watched Holmes shift against the background stars of Perseus. I tracked with the naked eye and binoculars, and watched the coma expand and dissipate in my telescope. It was mesmerizing.

The second was 103P/Hartley, which I observed with fellow PVAA member Steve Sittig at the observatory on the Webb campus in October, 2010. The sky was not particularly clear that night and we had a devil of a time finding the comet, even in the observatory’s pier-mounted GoTo C14. Eventually we found a fuzzy spot that moved against the background stars in a matter of minutes. That was a novel experience for me. With Holmes I only looked from night to night, not hour to hour or minute to minute, so I never got that little thrill of going to the eyepiece and noticing that something had moved.

My most recent comet was 168P/Hergenrother, which brightened by a factor of about 100 in early October, bringing this normally challenging object within reach of backyard telescopes. I tracked it down for the first time at the All-Arizona Star Party, then from Mount Baldy a week later, then from the Salton Sea a week after that. Each time I sketched the position of the comet at different times so I could record its progress against the background stars.

This year may be a big year for comets, with two that will hopefully reach naked-eye visibility. The first is 2011 L4 PANSTARRS, which was first detected by the Air Force’s automated PANoramic Survey Telescope And Rapid Response System. It should max out this March. Possibly even brighter will be 2012 S1 ISON, a sun-grazer newly arrived from the Oort Cloud. If it survives its extremely close pass by the sun—less than a million miles—it could possibly become bright enough to be seen during the day. Oddly enough, ISON is supposed to become bright enough to see in amateur telescopes in, you guessed it, October.