OASI: C/1996 B2

In the early morning of 31 January 1996, the Japanese amateur astronomer Yuji Hyakutake, using 25x150 binoculars, discovered a comet that was later named after him and designated C/1996 B2. At the time of discovery, the comet was already in the final months of its journey towards the Sun after travelling for approximately 8000 years from the most distant point in its very elongated orbit. The added coincidence that the comet would be almost due north when it crossed Earth's orbit on 26 March, and would be at its closest approach on the night before at a distance of only about 16 million km, certainly made it the surprise arrival of the century. Even in early February, estimates of apparent brightness indicated that it was going to be special! By the end of February it was clear that the comet was indeed exceptional and could turn out to be one of the best of the 20^th century, and that observers in northern latitudes would get the best view.

By early March, news of the comet had not reached the popular press but it was only a matter of time before this would change. At this time we had no plans to open Orwell Park Observatory to the public to observe the comet; we were going to wait until National Astronomy Week at the end of September for our annual Open Weekend. However, in view of the predictions of a spectacular apparition of Hyakutake, we decided in early March to open the observatory over the weekend Saturday 23 March to Monday 25 March.

The weather had been particularly dull during February and early March, but there was time for it to clear up and spring was supposed to be coming! Several pictures taken from locations favoured with clear skies appeared on the Internet and the press finally started mentioning Hyakutake - gradually, the public began to take notice. However, the cloud cover over most of the UK (and particularly East Anglia) refused to disperse. With only days until the Open Weekend, few people had actually seen the comet and the prospects did not look good. However, some of our members don't take this sort of thing lying down, and two of the more enterprising, Pete Richards and Mike Harlow, travelled to Tenerife where they obtained several splendid pictures of Hyakutake: some of Mike's best are below.

The Open Weekend arrived. Saturday was a dull, grey, cold day followed by an even more dull, grey and cold evening. A few visitors did venture out to the observatory, where we gave them a tour of the building and a lecture on comets illustrated with pictures downloaded from distant lands via the Internet, to give an impression of what they would have seen had skies been clear. Sunday was also cold, grey and damp with a similar if not colder evening. Another enthusiastic group of visitors arrived and again we treated them to observatory tour and comet lecture. Fortunately, the visitors were understanding in regard of our plight with the weather.

Monday too started cold and grey, but perhaps brighter? By evening, there was still a layer of cloud obscuring the sky but a very pale Moon was shining through. Was there going to be a chance of observing the comet? At first things looked as bad as ever, so we started the observatory tour and comet lecture for the thirty or so visitors that had braved the weather. About half way through, our car park attendants, Roy Gooding and Martin Payne, ran in to interrupt with news that they had seen a faint fuzzy glow near the zenith. We immediately abandoned the lecture and positioned the dome to view the comet. After a few minutes of dark adaptation we could just discern with the naked eye a fuzzy glow high in the northern sky. The 26 cm Orwell Park Refractor revealed a small but distinct hazy nucleus through the cloud with a surrounding glow that appeared to be positioned off centre. Even though the comet was barely visible through the cloud, the excitement of both members and visitors was tremendous, largely because for many, this was the first glimpse of the comet.

The excitement on Monday evening marked the end of our rather cloudy and generally disappointing Open Weekend. However, on Tuesday 26 March the weather began to clear and by evening there were extended clear patches. Although the weather did improve towards the end of the week the Moon was also rapidly approaching full (which tended to obliterate faint features in the comet's tail) and the distance to the comet was rapidly increasing. Overall, Tuesday was the best night of that week. David Payne observed the comet by eye and with binoculars (both 7x50 hand held monocular and 11x80 tripod mounted). He reported that the tail was magnificent and he could discern it stretching at least 20°! On Wednesday night the Orwell Park Observatory was again open for members. Although officially not open to the public, we had as many visitors as on any of the nights of our Open Weekend! However, by Wednesday, a combination of slight haze, the very bright Moon, light pollution over Ipswich and the comet fading had caused the tail to shrink to less than 5° visibility by eye.

The remainder of the week was clear but the Moon interfered significantly with naked eye observations. The nucleus appeared smooth and featureless in amateur telescopes up to 25 cm aperture. The next event of significance was the total eclipse of the Moon on 03 April. A lunar eclipse is certainly an event worth observing in its own right, but in this case it also furnished an opportunity to observe the comet for the first time since Tuesday 26 March in a comparatively dark sky. In the event the eclipse was spectacular, the Moon turning deep red at totality, just after 12.30am on the morning of 04 April, but the comet was at low altitude and affected by light pollution. Rather indifferent weather followed the lunar eclipse, with the next good observing night being Wednesday 17 April. On that evening, skies were clear and there was no Moon. The comet presented a magnificent spectacle with a clearly defined dust tail and a very distinct bow shock in front of the nucleus which then swept back in a graceful arc to merge with a magnificent tail. Thereafter, Hyakutake headed rapidly towards perihelion, and dropped rapidly towards the horizon as the sun set. The apparition for amateur observers had ended.

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