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Comet 1P/Halley, 05 October 1985 - 17 April 1986

Historical Background

Halley's Comet (formally designated comet 1P/Halley) is named after Edmond Halley (1656–1742). It has a periodicity of approximately 76 years and records of its observation go back to 690 BC. Chinese astronomers recorded every apparition of the comet for over 2000 years from 240 BC to 1835 AD. (Until 1984, there was a missing observation from the Chinese record: the apparition of 164 BC. However, in 1984 astronomical historians deciphered a Babylonian tablet in the British Museum and found a description of a comet in 164 BC and its next apparition in 87 BC: this could only be Halley's Comet!) Investigation of the Chinese records shows that the comet has not faded significantly throughout the last 2000 years. Even now, it is the only bright comet whose apparitions can be accurately predicted.

Halley's Comet, like so many others, has been considered in historical times a bringer of doom and destruction. Some of the most notable apparitions of the comet, many associated with catastophes, were as follows:

Preparation For The 1985-86 Apparition

During early 1985, a wave of excitement about the prospect of observing Halley's Comet spread through OASI (as indeed it did through many astronomical associations). A notice in the OASI Newsletter in January 1985 informed members about commercially-organised observing expeditions to provide the best conditions from which to observe the comet.

In early 1985, the UK 3.5 m infrared telescope in Hawaii was one of the first to detect the return of the comet, beyond the orbit of Jupiter and too faint to be seen in visible light. However, initial observations indicated that it was circa 20 km in diameter and, despite its distance from the Sun, already surrounded by a halo of dust. In its 1910 apparition, the head of Halley's Comet expanded to some 450,000 km in diameter and its tail to some 30 million km in length, and the object passed relatively close to the Earth, making it a spectacular sight. Unfortunately, during the 1985-86 apparition, circumstances were much less favourable, as the Earth and the comet were on opposite sides of the sun; in fact, the comet was particularly poorly placed for observation from the northern hemisphere and did not appear prominent to astronomers situated there. It was at its brightest during early April 1986 when visible from southern skies: best locations to observe were Southern Africa, Australia, New Zealand and Antarctica. Prior to the event, there were hopes that the comet's tail might be observed from the northern hemisphere rising above the horizon in mid-April; however, a full moon seriously hampered such observations. At the end of April 1986, the comet returned to northern skies but was faint as it raced away from the Sun back into deep space.

The 1985-86 apparition of Halley's Comet was the first observed from space as well as from the ground. Table 1 lists the space probes sent to rendezvous with the comet.
 

Probe Control Encounter Date
Vega 1 USSR 06 March 1986
Vega 2 USSR 09 March 1986
MS-TS Japan 08 March 1986
Planet A Japan 08 March 1986
Giotto ESA 13 March 1986

Table 1. Space probes scheduled to rendezvous with Halley's Comet.


OASI made its first attempt to find Halley's Comet with the 26 cm Orwell Park refractor during the early hours of Sunday 01 September 1985. At the time, the comet was in Orion, close to the stars 68 and 71 Ori. Unfortunately, the attempt was unsuccessful due to a combination of the faintness of the object, its low altitude, slightly hazy seeing and fatigue on the part of the observers! However, the comet was brightening rapidly (forecast to reach magnitude 12.0 by mid-September) so the observers were optimistic about the prospects of securing an observation before too long. The Committee of OASI offered to organise further early-morning observing sessions and proposed two projects to which members could contribute:

The Committee published in the September 1985 Newsletter the following guide to observing the comet (table 2).
 

Date

Mag.

Observe With

Notes

01 Aug 1985
13.8
Large telescope
Near Orion at dawn.
31 Aug 1985
12.7
Telescope
15 Sep 1985
12.0
Telescope
01 Oct 1985
11.1
Telescope
15 Oct 1985
10.2
Telescope / binoculars
Distance 240 million km in Taurus. Tail beginning to form.
31 Oct 1985
8.9
Binoculars
In Taurus.
15 Nov 1985
7.4
Binoculars
In Taurus.
27 Nov 1985
6.4
Binoculars
Nearest to Earth (inbound) at distance 100 million km in Aries.
15 Dec 1985
6.2
Binoculars
31 Dec 1985
5.9
Naked eye
Tail should be visible.
15 Jan 1986
5.1
Naked eye
Near Jupiter and crescent Moon in Aries.
30 Jan 1986
-
-
Comet too close to the Sun to be visible from Earth. Under observation by space probes. Tail at maximum length.
09 Feb 1986
-
-
Comet at perihelion, not visible.
15 Feb 1986
-
-
Comet too close to the Sun to be visible from Earth.
01 Mar 1986
4.4
Naked eye
Tail might be visible on SE horizon before dawn.
15 Mar 1986
4.5
Naked eye
Comet in Sagittarius: too far south to observe from UK.
30 Mar 1986
4.2
Naked eye
Too far south to observe from UK.
11 Apr 1986
4.0
Naked eye
Nearest to Earth (outbound). Best time for viewing from the southern hemisphere.
30 Apr 1986
5.0
Naked eye
Comet in Hydra; reappears in UK skies. Lunar eclipse on 24 April provides a good opportunity to observe comet.
15 May 1986
7.4
Naked eye / binoculars
30 May 1986
8.5
Binoculars
15 Jun 1986
9.4
Telescope
15 Jul 1986
10.7
Telescope
Comet in the morning sky at a distance of 500 million km. Only visible in large telescopes.
15 Aug 1986
11.6
Telescope
Only visible in large telescopes.
30 Aug 1986
11.9
Telescope
Only visible in large telescopes.
29 Jul 2061
-
-
Comet returns! But for observers in the northern hemisphere, circumstances are even worse than for the 1985-86 apparition.

Table 2. Observing guide for Halley's Comet.
 

Recovery Of The Comet By Members Of OASI

Following the first attempt at locating the comet from Orwell Park, the weather in the east of England deteriorated and by 23 September 1985, David Payne (then OASI Chairman), wrote an article in the Newsletter bemoaning the fact that no members of OASI had yet seen the comet. Fortunately, by early October the weather had improved and members of OASI recorded Halley's Comet photographically from Orwell Park and, one week later, observed it visually. The following extracts from the Newsletter for November 1985 convey the excitement of the occasion.

Photographic Recovery Of Halley's Comet, A J Smith

During early August 1985, it was decided that an attempt should be made to photograph Comet Halley using the Orwell Park 10" refractor. Unfortunately it was not until the night of 4/5 October that weather conditions permitted a sensible attempt to capture the much heralded object. Following a few phone calls, three members assembled in the observatory at midnight. Despite a nearly full moon close to the predicted field, photographic exposures were started by two of the members using Ilford HP5 B/W and 1000 ASA colour films.

After development, the 10 minute exposures on both films showed an object in the predicted position. A 250x200 mm print of the HP5 film (rated at 3200 ASA) revealed a definite image of the comet with a remarkable lack of background fog.

The following weekend, exploiting much clearer skies and the lack of interfering moonlight, another attempt was made. Again using HP5 film rated at 3200 ASA, a photograph taken with the 10" refractor, guiding on stars in the predicted field (no glimpse of the comet to the eye) produced star images down to mag 12.5 and an object exactly in the predicted position. Subsequently, a comparison with a drawing made by David Payne at the same time using his own telescope showed an object in the same place.
 

Sighted At Last, Halley's Comet! D B Payne

On Saturday 12 October 1985, we had one of the finest nights for some considerable time and it was the first real opportunity since the middle of August for a thorough search for that elusive wanderer, Halley's Comet. As I had been away for the previous ten days and hadn't had contact with members of the Society, I decided to search with my 10" reflector rather than travel to Orwell Park Observatory. However, I discovered on the following Wednesday that several members had taken the opportunity of the clear Saturday night to use the Orwell Park Refractor to search for the comet.

Although the comet would have risen about 10.00pm (BST), my eastern horizon is obscured by houses and it was about midnight before the region of sky containing the comet was visible from my observatory. At 00:05 hrs (Sunday morning) I opened the observatory and, using binoculars, began to familiarise myself with the relevant area of sky. There was no sign of the comet in the binoculars and I started to use the telescope, first with my lowest power and widest field eyepiece, a 32 mm Erfle. This gives a magnification of about 50x with almost a 1° field. I first identified the two stars 68 & 71 Orionis and then using the Sky and Telescope star chart as reproduced in last month's Newsletter, I slowly "star hopped" towards the predicted position of the comet. When I had the correct region of sky centred in the eyepiece, although I could identify all the stars in the field in the star chart, there was no sign of the comet! I decided to increase magnification to darken the sky glow. Just before I changed eyepieces I glimpsed a very faint fuzzy patch but it was so elusive that I couldn't properly position it against the background stars. I then switched to a 20 mm Erfle giving approximately 80x magnification. This darkened the sky significantly and at 1.15am on Sunday 13th October I had my first definite view of Halley's Comet.

It appeared as a very faint misty patch in the centre of which could be glimpsed, with averted vision, a small, almost stellar point. It was reminiscent of the nucleus of a faint spiral galaxy. I increased the magnification to 200x using a zoom Kellner eyepiece and then went to 280x with a 6 mm orthoscopic eyepiece. At this magnification, the stellar-like nuclear region was clearly visible with a surrounding faint circular glow approximately 30-40 arcseconds in diameter. I decided at this time to go in and have a cup of coffee and then come out and draw the field. I left the telescope tracking the comet and came out again at about 2.00am. After about 15 minutes of dark adaptation I drew the field shown below. However in the half hour or so that I had left the telescope a slight mist had come up and I had lost about half a magnitude of sensitivity. There were several other fainter stars not shown on the drawing or on the star chart that were clearly visible when I first sighted the comet. By the time I had finished recording the field the comet was becoming difficult to see (although I could still see all the stars shown on the Sky and Telescope chart. The comet was in fact considerably fainter than I expected it to be and I estimated its magnitude as around 12.5. The faintness was independently confirmed by the observers using the Orwell Park Refractor. They did not have an unanimously agreed visual sighting but did get a photograph of the region with a 15 minute exposure on HP5 film uprated to 3200 ASA. This negative has a faintly recorded object in precisely the same position as shown in the drawing (see report above by A J Smith).
 

Halley's Comet, M Barriskill

After an unsuccessful first attempt to observe the most famous of all comets on 27 August 1985, when it was probably too faint for my 8.5" reflector (the BAA magnitude prediction being 12.8), I have now made two successful visual observations, on 12 and 14 October.

On 12 October, I used binoculars to locate the general area and then a wide field eyepiece in the reflector to find the exact position. At first there was no comet to be seen but after nearly 30 minutes of searching I started to suspect a very faint object in the predicted position. It could be glimpsed only with averted vision at first but with the sky transparency improving I became increasingly certain that it was Halley's Comet. I estimated the brightness at magnitude 11.5, a full magnitude fainter than most predictions, and the size at approximately 2 arc-minutes. It was generally diffuse but the nucleus was visible with high magnification. The naked eye limiting magnitude by this time was six.

The observation on 14 October was much the same as the previous one, with a delay before the comet became visible due to low altitude, but by 00:20 UT it was directly seen. Both the size and brightness were the same as on the 12 October.

Hopefully these will be only the first observations of many of this long awaited and much heralded comet!

The following images show the first sightings of the comet by members of OASI.

19851005_0033_1P_AJS.gif Ten minute exposure, prime focus, Orwell Park Refractor, 05 Oct 1985, 00:33 UT. Ilford HP5 film "push" processed to 3200 ASA.

19851013_0210_1P_AJS.gif Ten minute exposure, prime focus, Orwell Park Refractor, 13 Oct 1985, 02:10 UT.

19851013_1P_sktch_DBP.gif Sketch of star field around Comet Halley, 13 October 1985, 01:15 UT, David Payne, 10" reflector, 280x, slight mist.

Further Observations

Once the comet had been located, further observations were obtained at Orwell Park Observatory and at members' homes. The following extracts from the OASI Newsletter provide details.

Observations Of Halley's Comet During November 1985, D B Payne

On Saturday 02 November, I made my first observation of Halley's Comet of the month. It was four days from full moon but the bright gibbous moon was still causing significant interference and a slight haze did not help matters. However using the Sky and Telescope chart I quickly found the comet with my 25 cm reflector about 0.25° to the west of 109 Tauri (η Tauri). I have a 75 mm Maksutoy telescope attached to the 25 cm reflector but there was no sign of the comet in the smaller instrument. In the 25 cm telescope the nucleus appeared more diffuse than in my first observation on 13 October and, in addition, it was not central in the surrounding diffuse glow, but offset to the north. This suggested that a tail might be forming but, due to the acute angle subtended to the Earth and the faintness of the object, it was not yet clearly visible. In the 25 cm reflector with an Erfle eyepiece giving 80x magnification, I estimated the diameter of the diffuse region to be about 40".

Sunday 03 November was another clear night and the Moon was less of a disturbance although there was still a slight haze. Finding the comet was very easy this time using the 25 cm reflector. At 11.30pm I was able to see the comet distinctly in the 75 mm Maksutov and I attempted to find it with binoculars. At 11.40pm I could just make out a fuzzy patch using averted vision in 10x50 binoculars. This was my first binocular observation of the comet.

Monday 04 November was cloudy but Tuesday again afforded clear skies (despite it being bonfire night). The Moon had waned and did not interfere and I found the comet without difficulty in 10x50 binoculars as a roundish misty patch. In binoculars however it displayed fairly uniform brightness without a defined nucleus region. I estimated it to be about 10' in diameter.

Wednesday 06 and Thursday 07 November were both cloudy. Friday 08 was also cloudy but with some clear breaks and I just managed to glimpse the comet with binoculars.

Saturday 09 was also cloudy but on Sunday 10 November some reasonably clear skies permitted further observation. Again I easily found the comet with binoculars about 2° E of the small arc of stars 72, 69, 65 and 67 Tauri. Using binoculars I estimated its diameter to be about 13'.

Monday 11 November was again clear but when I tried to find the comet with binoculars it apparently was not there! The seeing was fairly good and the sky was dark. The comet was lost in glare from the star 65 Tauri (magnitude 4.36), to which it was in close proximity!

On Tuesday 12 November , I again found the comet without difficulty using binoculars. By now the coma could be seen against the surrounding glow and the shape had become triangular hinting at a tail.

Bad weather prevented further observations in November.

19851112_1P_DBP.gif Star field around Halley's Comet, 22:45 UT on 02 Nov 1985, 10x50 binoculars & 25 cm reflector. (David Payne.)

19851102_1P_DBP.gif Star field around Halley's Comet, 21:30 UT on 12 Nov 1985, 10x50 binoculars. (David Payne.)

An Observation Of Halley's Comet In December 1985, D B Payne

December was generally a hopeless month for astronomical observations, at least from the Ipswich area! On the few nights that it was possible to observe the comet at Orwell Park Observatory we were inundated with visitors wishing to obtain a glimpse of the elusive object. Not wishing to turn away interested members of the public meant that we have not been able to carry out a serious observational programme as intended.

Despite the generally awful weather during the month, there was one night, Saturday 07 December, with excellent seeing conditions. On that night I started observing the comet at home at 9.00pm with binoculars. The comet was easily visible about 0.5° E of the pair of stars 31 and 32 Pisces. About 15 minutes later I could distinctly see the comet with the unaided eye - my one and only naked eye observation so far! In my 25 cm reflector the comet was a glorious sight and for the first time I could make out significant structure. By this time I had half a dozen visitors all wishing to see the comet through the telescope, and I was not left on my own to draw it until just after 10.00pm - unfortunately, by this time, it was beginning to sink down into a slight haze in the south west and I was unable to discern the detail that I could earlier.

The drawing below shows a rough sketch of what I observed in the 25 cm using a 50x magnification Erfle eyepiece. The nucleus of the comet was almost stellar. Surrounding the nucleus was a bright coma fading to a fainter and more diffuse region that stretched to a tail at least 1.5° long towards the north-east. In "front" of the comet was an arc of material about 1° wide which appeared almost detached from the coma/tail region.

This was without doubt the best observation that I have made of the comet to date, and it could easily remain such unless we get some excellent observing conditions in April 1986. As an indication of the excellent seeing conditions of the evening, when observing the Orion Nebula (M42) I could see the two 11th magnitude stars in the trapezium clearly and steadily. Also, for the first time ever, I could distinctly glimpse the Merope nebula in the Pleiades!

The following images illustrate the comet as observed by members of OASI on 07 December 1985. Alan Smith used the 100 mm telescope, co-mounted with the Orwell Park Refractor, to guide the main instrument while the photograph was being exposed, a process that he described as exhausting!

19851207_1P_DBP.gif 22:00 UT; nucleus and coma, 25 cm reflector, 50x, excellent seeing but slight haze, David Payne.

19851207_2015_1P_AJS.gif 20:15 UT; Orwell Park refractor, 15 m exposure, prime focus, Alan Smith.

Halley's Comet From "Down Under", A J Smith

In early April 1986, after two and a half years planning, two members of OASI set off on what must be the most ambitious observing trip yet undertaken by members of the Society. Roy Cheesman and I travelled through sub-zero temperatures and a blizzard from Ipswich to Gatwick to board a flight to the southern hemisphere to observe Halley's Comet. The trip was organised by Explorers Travel Club and included Patrick Moore for some of the itinerary. We left the UK on 03 April 1986 and, by careful planning (!?) managed to book a window seat on the Boeing 747 that would enable us to get our first glimpse of the comet at 12 km altitude outside the airport of Abu Dhabi, the second of many stops on what felt like a world tour en route to Australia!

I brought with me the following equipment for observation and imaging. It pushed the 20 kg weight limit on the flight to the maximum!

AJS_eq_gunsight.png The gunsight.

AJS_eq_DC_ctrl.png Stepper motor drive and DC motor controller.

AJS_eq_imaging.png The complete setup. Note the piggyback guide scope and flimsy tripod.

AJS_eq_eyepiece.png Homemade guide eyepiece showing cross wires made from fishing line (R) and hole to allow illumination by LED (L).

Thirty six hours after take-off from Gatwick we landed in record April temperatures at Sydney Airport. After extricating ourselves from the clutches of Australian immigration officers (Roy seemed particularly to attract close scrutiny) we boarded a coach for the short journey to our hotel. Here we would spend a night relaxing. The first night provided a taste of things to come, and we eagerly scanned the magnificent southern skies between clouds (the only clouds that we saw for three weeks!)

Before setting off from Sydney by coach the next day, I had to find a source of 24v power to enable me to charge (and recharge frequently) the power supply of the electrically driven equatorial mount. After negotiations with the coach driver and some dismantling of various parts of his pride and joy, a supply was provided via the dashboard.

The first day of the trip we spent touring Sydney Harbour by boat followed by the drive to Dubbo (a small town near Parkes Radio Observatory, the radio telescope used to chart the progress of the space probe Giotto to the comet a couple of weeks previously). The day proved to be only the first of a succession of superlative sights, including a conducted tour of Parkes Observatory, fantastic scenery of the Warrumbungle National Park, Siding Springs Anglo-Australian Telescope, Woomera Rocket Range, Coober Pedy opal mining town (where everything happens underground), and much else.

Our itinerary was as follows (dates in April 1986):

06: Sydney and Bathurst,
07: Dubbo and Parkes Radio Observatory,
08: Coonabararan, Warrumbungle National Park and Siding Springs Anglo-Australian Telescope,
09: Broken Hill,
10: Port Augusta,
11: Woomera and Coober Pedy,
12: Kulgara,
13: Ayres Rock,
15: Henbury meteor craters and Alice Spring,
16 at 01:38 crossed the Tropic of Capricorn, then on to Tennant Creek,
17: Katherine,
18: Darwin again.

The southern skies can only he described as magnificent. We could see stars from horizon to horizon and became lost in the rich starfields of the Milky Way and Magellanic Clouds with easily recognisable constellations such as Orion appearing oddly upsides down and travelling backwards.

And what of Halley's Comet? Well, similar to the experience in the northern sky it was less than spectacular to the naked eye with only a 5° tail visible. However, using telescopes and binoculars we could see the tail undergo various complex changes from night to night. Three images are shown below (all were captured on Ilford HP5 film, 400 ASA push processed in Ilford ID11 developer to 1600 ASA):

19860411_1P_AJS.png 11 April 1986.

19860412_1P_AJS.png 12 April 1986.

19860417_1P_AJS.png 17 April 1986.

We also witnessed other astronomical sights that were truly splendid, including most of the planets, the zodiacal light and a partial eclipse of the Sun. Our last view of Halley's Comet, to complete our tour of Australia, was probably the most bizarre from the perspective of the British psyche - at 7.00pm, from a swimming pool with tropical palms waving overhead, night time temperatures of over 85° F and a glass of something cool to enjoy!

We brought back nearly 1000 slides and memories that will last a lifetime. We'll host a slide show and talk at the Friends Meeting House on 20 June where we hope to be able to share some of the sights of Australia and show spectacular slides of the heavens.

Halleys Comet Open Days

The high public profile of Halley's Comet meant that many astronomical events were organised throughout the UK to coincide with its apparition. OASI opened the doors of Orwell Park Observatory on three occasions to enable the public to view the comet:

Unfortunately, the weather was not kind to the visitors and clear skies were rare on the open days!


David Payne & Roy Cheesman