Recollections of Hyakutake by M.Mobberley I first heard of Comet 1996 B2 Hyakutake during the somewhat frantic (for me) week at the start of February '96. The week was complicated by a BAA meeting, four Astrofest lectures and the first clear night for five weeks. In addition, there were a number of reasonable comets to observe, but they were all morning objects. These were the original Hyakutake 1995 Y1, Honda-Mrkos-Pajdusakova (making a 0.17 AU close approach to Earth on Feb 4/5) and the brand new discovery Szczepanski. As one might have predicted, the morning of Thursday Feb 1st, following the BAA meeting on the previous day, was crystal clear (skies always clear when you are at an Astronomy Meeting) and I felt obliged to observe the comets I had been speaking about only hours earlier. I got some reasonable images of Hyakutake (95 Y1) and the much more diffuse Szczepanski, but little did I realise that another Comet Hyakutake had already been discovered in the morning sky. The next morning marked my first visit to Astrofest and before setting off I decided to check my E-Mail. Upon logging on I was somewhat amazed to find that this character Hyakutake had already discovered his second comet, although at around 10th or 11th mag it did'nt seem particularly exciting. "Just have to wait for the orbit" I thought. During my two days at Astrofest I saw a number of familiar faces and one new one, the experienced Canadian Comet Observer Chris Spratt, from Canada. I was particularly pleased that I remembered to dedicate my Hale-Bopp talk to the memory of Harold Ridley who had died exactly one year earlier, on Feb 3rd 1995. Returning home on the Saturday evening I breathed a sigh of relief that my four talks had gone well and, with things looking fairly quiet in the Night Sky, I could have a bit of a rest. What a foolish notion! Even as I had been summing up in my talk 'Hale-Bopp: The Comet of the Century' the orbital elements of the new Hyakutake were breaking, showing that another Comet was already about to challenge for this title. On the afternoon of Sunday the 4th the phone rang. It was Guy, who I had last seen the previous day just after my Hale-Bopp talk. Guy's first words were along the lines of "You can forget about Hale-Bopp now, this new one is going to be much better!!" Guy asked me to look at the precise circumstances of the Comet's close approach to the Earth so he could put something in the next TA. I spent the rest of Sunday looking at twilight, moonrise, moonset and Comet Alt-Az data and E-Mailed Guy my prospects that evening. The close approach circumstances were truly mouth-watering but there were two problems. First, would the comet follow a healthy brightening curve in the next seven weeks? Honda-Mrkos-Pajdusakova was 0.17 AU from Earth just after Astrofest but was hardly a spectacular object. Secondly, for the days around close approach the weather was crucial. Bearing in mind the pitiful overcast weather we had experienced in the UK from November through to early February, surely things had to improve? As the weeks of February ticked by it became painfully clear that there was remarkably little changing in the British Weather, especially in the South East. A huge and rock-steady high pressure area was stuck like a leech over Russia and the weather fronts coming across the Atlantic, week after week were just grinding to a halt over the UK. The comet was almost stationary at Declination -23 at this time so it was not yet very favourably placed for UK observers. At the Feb 24th BAA meeting I advised the members to start praying for clear skies. I saw the Comet once in February, on the 27th, at around mag 6. It was obviously brightening even more rapidly than we had hoped. Calculations by Jonathan Shanklin and later, by myself, indicated a very steep log r curve in February. Unfortunately this co-efficent became far less impressive once the comet had passed the Earth. As we moved into March and the comet slowly started to crawl northward, excitement over the close approach became tinged with frustration, misery and utter despair in the UK. We were now not far short of the Spring equinox but the High Pressure over Russia had barely moved at all. The UK was still immersed under totally dense cloud, day and night, with bitterly cold East windows compounding the misery. Surely, this weather could not continue. Where we going to miss the best comet close approach for 400 years because of the cloudiest spell of weather for 400 years? On Tuesday the 12th of March Nick James and myself met for our weekly assessment of the past week in Astronomy at our bi-weekly venue, the Horse and Groom Public House in Galleywood, Chelmsford (about a mile from my Chelmsford address and the 0.49m Newtonian). This was no ordinary meeting though, it was a crisis summit! Hyakutake was already an easy naked object but Nick had'nt seen it at all and I had'nt seen it for two weeks! In fact neither of us had seen the Sun for two weeks. Following a bizarre incident involving the hypnotic pub dog (which appeared to be suffering from a mild form of rabies) our thoughts turned to emergency plans for travelling to Denis Buczynski's observatory or leaving the UK. It was slowly becoming clear that the past four months of almost un-broken cloud was set to continue. In the next week our plans to leave the country accelerated exponentially but we did catch one glimpse of the comet from the UK on the night of March 16th/17th. I was spending the weekend (as usual) at my parents home at Cockfield in Suffolk. At around 10.00 pm I could scarcely believe my eyes! Looking out of an upstairs window I was certain that I could see a couple of stars. My excitement at glimpsing a few stars may seem ludicrous to foriegn readers in better climes, but the UK weather really has to be experienced to be believed. I phoned Nick in Chelmsford at 1030pm and he sounded equally excited that I had just glimpsed two 1st mag stars! He promptly threw all his camera equipment in his car and drove like a madman up to Cockfield, some forty miles to the North. To cut a long story short we actually saw the comet that night, in brief gaps. It was a testimony to the comet's brightness that it was a superb object in the 14 inch reflector, even though we never glimpsed stars fainter than 3rd mag with the naked eye that night. Our frayed nerves were slightly calmed by the sight of the comet but after seeing the 5 day weather forecast later that day we resolved to fly to Tenerife for the close approach nights of March 22/23 to 25/26. In the week before we had consulted with a number of fellow observers/advisers including Mark Kidger (resident on Tenerife), Hazel McGee, Paul Doherty and George Alcock (a dedicated weather-watcher, as well as a discoverer). George advised me that the clouds over the UK would part after the comet passed the Earth, due to the draft from the comet's tail! As it turned out he was dead right!! Also, our numbers had now grown to three. Glyn Marsh had joined our expedition as the weather in Lancashire was now almost as bad as in East Anglia. In the last few hours before we departed I received an E-Mail from John Rogers, BAA Jupiter Section Director, asking if he could join our party and escape from the 'Miasmic Swamp' of East Anglia. Unfortunately, there was no way we could get an extra plane ticket at such short notice, but luckily, John did manage to get to Spain and had excellent views of the comet. By a strange coincidence a number of other BAA members had left the country that week for reasons unconnected with the comet. Richard McKim was in the Italian Alps on a school trip, but the skies there proved to be cloudy. Michael Maunder though was in Tenerife, and we bumped into him at the airport. Returning to the story; on Thursday the 21st of March, Nick and I drove up to Glyn's house at Catforth near Preston. The night before was spent frantically checking our equipment and manufacturing (!!) a guide telescope for Glyn's Vixen GP Mount! Denis Buczynski also came down to Glyn's house to wish us the best of luck. We owe a debt to Glyn's friend Andy Sefton who overhauled the mount the night before we left and donated a very useful camera orientation platform to our expedition. On the Friday morning the three of us set off for Manchester Airport and our flight to Tenerife. After the splendid meal that Glyn's wife had prepared for us the previous evening it was a miracle that the plane took off! Upon landing at Tenerife we were greeted by Mark Kidger, without whom our four days in Tenerife would definitely have been a disaster. By a strange coincidence, Nick and I had travelled to Tenerife exactly 10 years earlier, to observe Halley; but this time we had much better equipment and a contact on the island. Mark had already booked us into the Hotel Nivaria in La Laguna at a special rate reserved for visiting astronomers. And damn it, we were visiting astronomers, travelling to Tenerife under our own funds and getting professional results. La Laguna is in the North-East of Tenerife and has easy access to Izana Observatory and lower altitude observing sites. More importantly, it is well away from the Southern 'Lager-Lout' end of Tenerife. To describe in detail our hectic four days on the island would take an entire booklet, but the most memorable events are well worth recounting. This was not a relaxing four day holiday, we were there to see and photograph the comet; nothing else mattered. A brief summary of the experience would be:- 1. A totally disrupted sleep pattern 2. A totally disrupted eating schedule 3. Hypothermia and travel sickness 4. A post-traumatic stress disorder inducing one-way system 5. Car journeys back down the icy mountain roads at dawn with EVERYONE in the car asleep. 6. A bank balance some three-hundred plus pounds lighter (each), most of which was due to the cost of a single fish (the size of which would have interested Norris McWhirter). 7. A broken wing-mirror 8. Once in a lifetime views of an awesome comet at the Zenith, with a 1.5 degree head and a 70 degree tail in an unbelievably clear sky. 9. Four clear night worth of STUNNING astrophoto's. Our first view of the comet and our first view of ANY comet with a naked-eye tail was at 23:23 UT on the 22nd. Mark Kidger had treated us to a traditional Tenerife restaurant meal complete with Octopus! A fellow Spanish amateur astronomer, David, had also joined us for the meal. As we staggered into the street in La Laguna, after the meal, we immediately spotted Ursa Major and, tracing the tail down to Arcturus, we could see two 1st magnitude stars; one of these was big and fuzzy! And this was from the middle of a fully illuminated street! It immediately struck me that this was not simply a comet observation; it was history in the making and it was now etched in my memory! Comets that are visible from town centres at midnight are not commonplace! After a few minutes gazing at the Comet + the tail from a darker spot behind the hotel the five of us (including Mark and David) set off for one of Mark's prime observing sites on the extreme northern coast of Tenerife, at Punta Hidalgo. Our first night of observing Hyakutake had started. Strangely, the engineers at Opel did not cater for the requirements of five astronomers and a couple of hundredweight of camera equipment when they designed the 1.4 litre Corsa! However, despite the insults we hurled at the car on our trip, it served well. Mind you, after we had thrashed it, it was unlikely to serve anyone else well in the future! Over the next four nights we gazed at the comet through the crystal clear skies of Tenerife. Whether any other observing experience in my lifetime will be so memorable I seriously doubt. We will have to wait to see how Hale-Bopp performs but that will not be passing within 0.1 A.U. of Earth and will not be at the zenith at it's peak! The following summary of the four nights of observations has been lifted straight out of my observing log. ---------------------------------------------------------------------------- Night 1 1996 March 22/23 at 0300 UT Site: Punta Hidalgo on the NE corner of Tenerife. On the sea shore. The Comet's tail was at least 20 degrees long in PA 230 degrees to the naked eye. The head was roughly mag 0.5, very similar to Vega. The head was remarkable. A distinctly bluish colour in 11x80's. A starlike nucleus was surrounded by a classic hood and a larger tear-shaped coma which was 1.5 degrees in diameter. The tail stretched well beyond Arcturus, which was certainly brighter than the head. Night 2 1996 March 23/24 0000 UT at the Puerto de Guimar beachside Hyakutake Star Party. The Mayor had ordered the city lights turned off for 90 minutes. 0300 UT at 7000 feet near to Izana in a biting icy wind. 0400 UT at 5500 feet at Chipeque. At this altitude the tail could be traced to at least 40 degrees. The head was slightly fuzzier tonight and not as sharply defined. Still around mag 0.5 though and still 1.5 degrees in diameter and distinctly blue. Also at this site were Spanish Punk Astronomers who insisted on playing the Spanish Punk equivalent of Sinatra's 'My Way' all night!! Night 3 1996 March 24/25 from Chipeque (5500 feet) above La Laguna An absolutely crystal clear and freezing night at 5500 feet. The Milky Way looked irritatingly like cloud. I could'nt believe it was the Milky Way! This was a 9 hour observing session from 2200 - 0700 UT (dawn) We were close to death after this one! At 2240 UT we spotted a tailward pointing spike within the coma in the 11x80s. It was about 2' long Tail was 20-25 degrees long with direct vision and well over 40 degrees long with averted vision. At times I was sure I could see 60 degrees plus of tail!!!! (After moonset) The head was even more fuzzy tonight, especially when compared to Night 1. The comet totally dominated the night sky and caught your eye when you were just walking around, despite being at the zenith. A tail disconnection event was easily visible in binoculars and our photo's of this changing have to be seen to be believed! 4th Night 1996 March 25/26. Back on the seashore at Punta Hildago facing due North. 0240 - 0530 UT With the comet in the far northern sky this was a picturesque sight. Polaris was 28 degrees above the Sea and the head of the Comet was close to Kochab in Ursa Minor. The tail stretched through the gap between Alcor/Mizar and Alioth and was visible for 20 degrees with direct vision and at least 50 degrees with averted vision. The temperature was remarkably mild and we were sitting against the beach wall with the waves breaking on the North shore, looking out to sea at this awesome sight. A cruise liner on the horizon made it look like the Sky & Tel Hale-Bopp cruise advert!!! Comet's head was approx mag 0.9 to me and it stretched off at a PA of 225 degrees. My last view from the beach was at 0528 UT on the 26th. I next saw the Comet at 1934 UT out of the back of Glyn Marsh' Volvo rear window on the way out of Manchester Airport; i.e only 14 hours 6 minutes later. It was then virtually on top of Polaris. Now I know what the ancients must have seen in centuries and millenia gone buy....I can understand their terror! Remarkable.............. ------------------------------------------------------------------------------ Although I saw the comet on many more nights back in England, the view from Tenerife was far more memorable. The Moon had become a real problem by the 28th and the skies in the UK bore no comparison with the dark skies in Tenerife. However, the comet still had an impressive naked eye tail (even from Chelmsford on April 17th). We now have all the photo's back from our trip and a brief analysis of our best results is worth a mention. Kodak 2415 (expertly hypered by Glyn) and Fuji Super G 800 proved to be the best films. Due to the comets rapid motion of up to 2700"/hour during our trip, three to four minute exposures were the longest I was prepared to risk with the 85mm f/1.2 Aspheric Canon Lens. This would prevent the comet moving more than three arc minutes during an exposure (0.07mm at the film plane). Luckily, three minute exposures at f/1.2 (2415) and f/1.8 (SG 800) were absolutely optimum for reaching the Tenerife sky background,but NOT overcooking it. An examination of the negs reveals that the limiting stellar magnitude for the 85mm lens shots for both 2415 & SG800 was identical, at mag 12.7. The fine grain on the colour negs is remarkable for a 800 ASA film. Of particular interest was the tail disconnection event which occurred on the close approach night of the 24th/25th. Comet tails tend only to change significantly on photographs that are at least an hour apart. With evening comets the object usually disappears in the dusk murk an hour after astro-twilight; with morning comets, the sky is too bright an hour after astro-twilight. With Hyakutake being at the zenith at 230 am we secured images of the tail disconnection over a four hour period - a fascinating sequence. I have compared a couple of photos taken at 01:09-01:12 and 03:51-03:54 UT. In the intervening 2.7 hours the comet's head moved 2.1 degrees in PA 354, but the disconnected tail moved 1.1 degrees in PA 320. Also, an extra 1.4 degrees of new tail (230,000 miles worth!) sprouted in the gap during those 2.7 hours. As the old tail material seems to float away from the head, is offsetting at the nucleus drift rate optimum for imaging long comet tails?? Probably not; the best solution is probably to just use the fastest optics to freeze the comet in time - i.e. a professional Schmidt Camera. I'll have to re-mortgage the house! When will we get the chance to see such a monster at close quarters again I wonder? Swift-Tuttle in 2126 may be the answer to that. Can anyone please tell me how I can increase my lifespan to 168 years? Martin Mobberley