Comets: 3 for the price of 1! Get 'em while they're hot!!!

Comets are my favorite celestial objects. Whenever I hear that a comet has been discovered or recovered, I get a bit antsy. I wait for an ephemeris, wondering how bright it will get and what direction it is headed. I hope for clear nights during the dark of the Moon. When I see a comet, I know that I am observing something that is just passing through and will only grace our skies for a short time. Some comets are visiting the solar system for the first time, others for the first time in thousands or millions of years. Then there are the periodic comets, most of which have been observed and recorded many times before. Each one is different, but they all share a common origin very closely tied to the origin of life on Earth and the shaping of the solar system as we know it.

Even with the interest in comets brought about by the Shoemaker-Levy 9 collisions with Jupiter, I don't often get to share the experience of observing a comet. There are a number of factors that make comets less accessible to new skywatchers. First, we haven't had a bright comet in a while. Comets of 7th or 8th magnitude don't exactly jump out from the eyepiece, especially for someone who is not used to using a telescope. Second, comets tend to be brightest when they are near the Sun. This means observing right after sunset or, worse yet, right before sunrise. I know few people who will commit to getting up at 4:00 am just to (maybe) see a fuzzy patch. Finally, the same fleeting nature that makes comets intriguing means that there is only a limited observing window. A comet may be visible this week and gone the next, and with bad weather and moonlight one really has to be prepared to observe whenever possible.

So, my comet viewing is a lonely pursuit. A lone observer waits for the waxing gibbous Moon to set, as he prepares his telescope and finder charts. The temperature is about 15 degrees F, and an East Wind is keeping the skies clear but playing havoc with loose papers and 'scope covers inside the dome. The observer uses the telescope's setting circles to zero in on the first target, and the morning begins for real...

On 1996 February 1 between 1253UT and 1405UT (4:53-6:05 am, PST), I searched for the three bright comets visible in the morning sky. Here are my observations with a Celestron C-8 telescope from the James H. Karle Observatory at Lewis and Clark College in Portland, Oregon.

C/1996 B1 (Szczepanski)

This comet was just discovered a couple of days earlier, near the handle of the Big Dipper. By 4:30 am, it was nearly overhead, away from the worst light pollution of Portland. Still, I had heard that this comet was large and diffuse. Something every observer should know: If two objects have the same total brightness, the larger one will have a lower surface brightness and thus be more difficult to see. A diffuse comet of 8th or 9th magnitude could be a challenge. Using digital setting circles, I zeroed in on the place the comet should have been. Nothing. I made a few sweeps to either side and up and down. Still nothing. Then I remembered that I had the comet's position for 0 hours Universal time. It was now almost 13 hours, so to get the best position I would have to interpolate between today's and tomorrow's positions. I quickly did the math in my head and nudged the telescope in the correct direction. There! At the top of the field was one of the largest and dimmest smudges I had ever seen. I brought it into the center of the field, trying to shield my eyes from stray light to get the best view. It didn't seem to have shape or condensation. It was just...there. Not satisfied, I put a light pollution filter on a low power eyepiece. Sometimes these filters will improve a comet's view, sometimes not. The filter killed a few of the faint stars in the field, but the comet swam to the foreground. It was still a large, round, indistinct patch, but the southern part looked a bit more concentrated. I jotted down a few notes and made a sketch.

The comet was sighted at 1253UT, using the C8 at 71x. Near the zenith, the naked-eye limiting magnitude was 5.4. The comet appeared very diffuse, with little condensation. With an Orion Broadband Light Pollution Filter and 67x magnification, the comet was much more prominent and visible with direct vision. There was a slight condensation to the south, but no clear nuclear region. I estimate the total magnitude to be around 8.5, but the comet appears much fainter because of the low surface brightness. Observed coma diameter was 11 arcminutes and there were no prominent extensions. Degree of condensation was 2 on the 0-9 scale.

One down, two to go.


This comet promised to be diffuse as well. A periodic comet, it had already passed perihelion (closest approach to the Sun). It was headed in Earth's direction, so its apparent size was increasing rapidly. I missed seeing this comet before its perihelion passage, losing out to twilight glow and light pollution. Now I would get another chance. The comet was a short distance from the bright globular cluster M10. The previous day, an observer had posted on the Internet that the two objects were about the same total brightness. I was skeptical but hopeful nonetheless. I looked at M10 for a bit, then hopped around to its south.

This comet was a bit difficult to locate from a finder chart and ephemeris, due to its rapid motion. I finally pinned down its position. When I first saw it, at 1335UT, it looked like a replica of C/1996 B1. As I observed it more carefully, I noticed that it was both brighter and more elongated. There was a prominent nuclear condensation to the SE, and the northern edge of the coma appeared more defined than the others. Eventually, I could make out a tail extending 15' to the WNW. I estimate the total magnitude to be 7.9. Observed coma diameter was 9'. Degree of condensation was 4.

Although most comets develop tails when they are in the solar neighborhood, it is usually difficult to see these tails visually because of lack of contrast. Light pollution really complicates things. I considered myself lucky to even see this comet, and doubly lucky to see its tail. I pulled myself away from the eyepiece and prepared to hunt for the last comet of the morning.

C/1995 Y1 (Hyakutake)

I saved this comet for last. While it had a total brightness near that of the other two comets, other observers had noted that it was more condensed. Also, it was farther to the South and East in the sky, so I wanted to let it rise higher. It was a disappointment when I looked in the eyepiece and saw nothing. I re-interpolated its position from the ephemeris. Nothing. I swept the sky frantically before realizing that I had made an error of 1 degree in my math. A bit sheepish at forgetting how to subtract, I moved the scope a degree to the South and there it was.

As expected, this was the easiest and most condensed of the three comets. At 67x with filter, it appeared as a compact glow about 5' in diameter. There was no sign of a tail, and little elongation, but the N edge appeared indistinct and fuzzy. I estimate the total magnitude to be 8.4. Degree of condensation was 6.

Twilight seemed to come suddenly, as just 15 minutes after I located the comet it started to fade. Dawn was approaching. I moved the 'scope to M13, the Great Hercules Cluster, and marveled at its thousands of glittering points. I then closed the dome and sought a warmer environment. Three comets in a night was a new record for me, but I expect I'll break it sooner or later. I probably won't see 45P until its next favorable trip sunward. As for the other two, the Moon is nearly full. I'll have to wait a couple of weeks for another shot, and that's only if the weather cooperates. Who knows? By the next clear, moonless night, there may be another comet or two for me to track down!

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