MIRA 12
February 1986


Meeting Review

Friday the 13th September... the first meeting of the Society for the Autumn session and the second visit in less than a year by Mr.John Armitage, who once again delivered a very lively talk, this tine on Meteors and Meteorites.  He covered the the various physical and chemical differences between the stony, stony-iron and iron types.  Of these three basic types the stony meteorites are the nest numerous to be found and are referred to as chondrites - from the Greek word chondros, meaning a grain of seed, because of the minute spherical bodies that are characteristic of this particular class of meteorite.  The other two are less common as they are susceptible to erosion by the Earth's atmosphere.  The 11th October evening was initially booked for a talk by Mr. Paul Doherty on observing the planets, who would no doubt have illustrated his talk with some of his excellent observational artwork, for which he is particularly noted.  However, due to a last minute cancellation a number of members from the society rallied round to put on a very varied and convincing show.  So thanks to all for your co-operation.
The 8th November must surely have been the best meeting for many years, with an unprecedented attendance (110) of members and visitors filling A5 to capacity, along with names in the society register filling two pages.
Dr. Allan Chapman from Oxford was the invited speaker who held us spellbound for over an hour with what I can only call his sheer professionalism.
The talk concerned Halley the man, who, it transpired, showed great promise from a very early age as a very gifted mathematician.  With sufficient financial backing from his family Halley had the means and the skill to explore new horizons (quite literally), as at the age of 20 he conducted the first telescopic survey of the southern stars from the island of St. Helena.  Later be invented and produced a diving bell which wasn't superseded until efficient air pumps were developed 150 years ago, charted the seas to produce reliable magnetic bearing contour maps... and still found time to do a spot cf comet predicting!
A strange co-incidence that we should hear a lecture on Halley on Nov.8th - the day of his birth.
After the lecture a light buffet was laid on by the College catering staff, giving everyone a chance to do a spot of general socialising, to view the exhibition, and to examine some commercially made telescopes.
Before the close of the evening a special re-opening ceremony for the Observatory was conducted by the Deputy Lord Mayer of Coventry, Mrs W. Lakin.
A tape across the threshold was cut and a large sky rocket launched.  The Mayor and Mayoress of Southam were also in attendance.  The only disappointment of the occasion was the torrential rain which prevented any viewing of the comet itself - a particular disappointment to our guest of honour Mrs Dorothy Gibbs who remembered seeing Halley's Comet as a young girl in 1910. (Mrs Gibbs subsequently viewed the comet through my telescope — Rob Moseley)
During National Astronomy Week nearly 800 members of the public visited the Observatory, and the comet was well seen on three evenings.



Letter to the Editor

Dear Vaughn,
In response to your interesting points made in your article on the order of brightness of the Plough stars, I would like to add the following:
The magnitude sequence given as the answer to the exercise set in the March 84 edition of MIRA 6 were taken from the USNO Photoelectric Catalogue - which is acknowledged as a highly reliable source.  Therefore the "Cov & Works“ values can be taken as the correct ones.
Secondly, in answer to your query about the variability of Alpha (Dubhe), I have checked the lists of known and suspected variables in Volume II of Sky Catalogue 2000.  It is not listed.
It is true that Dubhe is the "odd man out" in the Plough.  Its colour is indeed warmer than the others, and this belies its radically different nature.  It is a giant star, of spectral class K, rather similar to Arcturus - whereas the others are all young blue/white main sequence stars similar to Vega.
However, one of the seven stars is a variable.  Epsilon (Alioth) is a short period variable with a period of 5.0887 days, fluctuating between mag. 1.76 and 1.79.  Full marks to anyone spotting this with the naked eye!
Yours Sincerely,
Rob Moseley.

Reply to Letter
Thanks for your kind response to one of the queries I raised in the March 1985 issue of MIRA 10.
I can't argue with the measurements compiled by the U.S. Naval Observatory Photoelectric Catalogue - but I've recently cone across a 1974 copy of The Astronomer, and the following nay be of interest.  A certain JW Kent had carried out a survey of some of the naked eye stars in the Plough and Alpha Uma (Dubhe) he reckoned to be about mag. 1.6, although its recorded as 1.95.  He continued to say that Dubhe was actually recorded by Lalande as variable round about 1770 and since forgotten.
Although I observed Dubhe with the naked eye as a red star and Patrick Moore describes it as orangy in his book "Astronomy", I was interested to see during our October meeting Barry Merrikin's excellent photo of the Plough where Dubhe appeared, I believe, as more yellowy - hence fitting its spectral classification as a giant K2 star.

V. Cooper (Editor)




Halley Observing Week at Southam

During the week from Monday 2nd Dec. to the following Monday members of the public were invited to a once in a lifetime view of Halley's Comet through society members telescopes set up in a recreation field near the home of Mrs Angela Turner at Southam.
The week as a whole was pretty poor except for the Tuesday and Thursday when there was a good response from the public which kept Angela, Barry, Alan and myself busy not only in keeping the comet in the field of view of our respective instruments but also answering an avalanche of questions... like "Where is it in the sky?"  "How far away is it?" etc.
The astonishing result of my first night (Tuesday) was that I could clearly see the comet move its position against two nearby stars during tae course of the night.
Thursday night (Dec.5th) started off in a similar pattern to Tuesday — initially a good start then cloud closed in for a short time and remained patchy till we closed at 10.30pm, but despite the clouds and a strong wind from the West people were still turning up in small numbers to view.
The interesting feature worth recording for tfie 5th was that the comet appeared bigger and brighter than it did 48 hours earlier.  This was perhaps due to 18 hours of constant rain which helped to produce a more transparent atmosphere.
Saturday Dec.7th had all the qualities of being a very promising sight but cloud soon closed in and remained for the rest of the night, causing an early termination to any further observing.
On the whole the people who turned up were very appreciative of our efforts while they either patiently waited for the clouds to clear or queued behind the telescopes for their turn to view.

Vaughn Cooper



First Sightings of Halley's Comet. . .

an Inventory of local Observers.

Name  Date  Time  Instrument  Location
Geoff Johnstone*  20/9/85  02.41        254mm spec.  Leamington
Angela Turner  20/10/85  04.45  102mm Refr  Southam
Barry Merrikin  5/11/85  22.00  200mm spec.  Rugby
John Richards  5/11/85  22.00        200mm spec.  Radford Semele
Rob Moseley  5/11/85  23.15  254mm spec.  Coventry
Vaughn Cooper  5/11/85  23.55  150mm spec.  Warwick
Lee Craner  9/11/85  21.30  10x50 bins.  Coventry
Alan Hancocks  11/11/85  20.00  165mm Refr  Coventry
Rickard Teasdale  14/11/85  22.09  165mm Refr   Coventry
I. Clarke  16/11/85  22.00       7x35 bins.  Bedworth
Paul Szrok  7/12/85  19.00  100mm spec.  Dunchurch
Gordon Coultrap  7/12/85  20.30  7x50 bins.  Fenny Drayton

*Photographic observation.





The Other Comet

By Mike Frost

You'll all, I'm sure, have read Rob Moseley's article in the last issue of MIRA on the other Comet - namely Giacobini-Zinner.
Plans for a US probe to Halley were shelved on cost grounds, but as I'm sure you know by now it soon turned out that everyone else ie. Russia, Japan, and the European Space Agency were able to send a probe or two.  The Americans, who are world leaders in interplanetary probe exploration seemed to have missed out on a new class of astronomical object.  However, they came up with an idea of diverting one of their existing satellites, a lunar orbiter, to go and take a look at Giacobini-Zinner.  The manoeuvre to accomplish this involved a close pass to within 100Km above the lunar surface to achieve a sling shot effect out of the Earth-Moon system.
On September 11th I985 the satellite, now renamed International Cometary Explorer, flew past G.Z. - beating its competitors by a clear 6 months.  Another first for Uncle Sam!
Conditions were not ideal, as ICE's scientific instruments were designed for lunar recording and there was no opportunity for a refit!  Nevertheless some fascinating data was returned.
Half a million kilometres from the comet ICE encountered streams of heavy ions travelling at high speed in a direction away from the Sun and likely to be associated with the comet.  The best explanation to date is that molecules have escaped from the cometary nucleus towards the Sun before being blown back
by the solar wind, a stream of lighter charged particles which originate inside the Sun.  It is the solar wind which is thought to shape the tails of comets.
Another popular theory on the structure of comets was given support by the discovery in the tail region, of ions which are related in structure to water.  The satellite's instrumentation was not sophisticated enough to identify the exact structure of the charged molecules (H2O, + HO and H30 are the most likely candidates) but the results suggest that the nucleus could be made up of ice.
The ICE crossed the tail of GZ and found it to be about 24,000Km wide, much wider in extent than earth-bound observations had suggested.
The GZ observations will be of immense interest when compared with those of Halley… and the USA have not missed out on cometary probing in 85/86.




Lunar Notes

Heraclitus   a unusual irregular enclosure with a central ridge. It adjoins LICETUS.

Licetus       a crater of 46 miles diameter, with uneven walls and a low central hill; the rampart has been broken on the south, so the interior connects with Heraclitus.

The drawing is not completed due to the sky clouding over; plus subtle detail that was on the fringe of visibility could not be added due to the unsteady atmosphere.
A prominent pair of craters when well placed.
Heraclitus a disintegrated "square", formation that is most distinctive.
The floor has a wealth of detail; bad seeing made only the prominent features discernible.  A large craterlet with a crater-pit next to it is seen in the southern part of the floor, the craterlet being dark grey, and the crater-pit black.  A craterlet is tucked; close to the central ridge.  The central ridge appeared more wall like.  Scattered hills are dotted over the floor, the most northerly of these has a black patch adjacent to it, which may be a crater-pit.  A terrace is in the west wall, which looks to have landslided in the centre, below of which is a narrow black depression in the wall.

Heraclitus D is a most prominent craterlet, that looks to have high walls in the S/W.  A very bright white patch on the floor is adjacent to the black shadow in the south.  I cannot go into detail with regards the N/W wall, as by the time I came to observe this area, seeing had deteriorated so much that the image was jumping about (this was at the end of the observing session).

Licetus the partner to Heraclitus, fit together rather like a jigsaw.
A craterlet in the northern wall of Heraclitus intrudes on the southern wall of Licetus.  A distinctive craterlet is at the foot of the west wall, with a lighter toned companion adjacent.  The S/W wall of Licetus intrudes into Heraclitus.  The floor showed two longish hills, and the floor adjacent to the
hills in the S/E was very light.  Three other craterlets are to be seen, a prominent one in the northern rampart, and two less conspicuous ones at the foot of the N/W wall.

The N/W wall has a terrace along the top.



DATE. . . . . . . 25th June 1985
TIME. . . . . . . 21h 55m - 25h 20m
MOON. . . . . . 7 Days
CONDITIONS . Steady, patchy cloud thickening, much quivering of image, atmos turb
INSTRUMENT . 102mm OG x186
LOCATION . . . Southam. Warwickshire
OBSERVER . . . Angela Turner



Licetus, Cuvier and Heraclitus


27th April 1985
20.40 - 21,10 UT

6" reflector x120 - 180
Seeing — Fair
Moon 8 days old
Observer - V Cooper

In this issue I thought I would include an observation of the same lunar feature by two observers during a different lunation, if only to show the different details depicted and drawing styles.

Heraclitus is a very complicated structure broken into its North, South and Eastern walls by Licetus, Heraclitus D and Cuvier respectively with a central ridge running N — S.

Licetus is a crater 46 miles in diameter without a wail in the South were it joins Heraelitus (illustrated in my drawing but not so clear in Angela's).  Also Licetus has a central hill, not noticed during my observation but a detail picked up in Angela's.

Cuvier is a 50 mile diameter crater with a wail rising to 12,000 feet above the interior



Solar Notes

Solar observations have been lacking in previous issues of MIRA, which is quite understandable as the Sun has been rather inactive for some time due to the approach of minimum of the sunspot cycle.  However, the two observations now published show the most interesting and complex active area I've been able to see this year.

I was fortunate to observe on two consecutive days, and this shows quite well the amount of E — W solar drift during 24 hours and also the physical change of detail within the larger active area shown.

V. Cooper





Letter 

Rev. Tim Gouldstone . . . the most Southerly Amateur Astronomer in the Country!

Letter from Tim and below is a brief extract along with a few of his observations. (Ed.)                              


I have sought out a local amateur astronomer who happened recently to have an article published in the BAA Journal.  He is Steve Anderson, of Chyraise Lodge Hotel, Goldsithney near Penzance.  He has an advert in the BAA Journal for June 1985 advertising his hotel as a place to stay for national Astronomy Week and say that he is 'most southerly telescope in the country', he was surprised to see me and also to find out that I had beaten him with having a 216mm reflector further south on the Lizard.  He is at 50° 6' and I am at 50° 3' N Lat.!

The site is quite good here and the first thing you notice over even the rural parts of N Warwickshire is the great transparency of the sky and of course the lack of light pollution, etc. on the southern horizon (there's nothing but sea beyond the Lizard for 700 km).
An interesting phenomenon is the beam of the Lizard light which sweeps over St. Keverne but is not obtrusive.

Observations with binoculars:

Sept 12th 20h-21h

Dark rifts in the milky way very conspicuous from Cygnus to Serpens.
The area to the W of Deneb shows signs of the 'North America' pattern which I could not see from Coventry without photographic aid!

The star cloud in Scutum is a beautiful sight, as is the 'Lesser Sagittarius Star Cloud' (M24) M16, M17, M18 form a line of clusters easily seen in binoculars.  Further south, there was M8 and M20 and M22.

Exploration of the S horizon revealed hitherto unseen areas such as the obscure constellation of Microscopium (alpha, beta, gamma) and all the major stars of Piscus Australis.

In Scutum M26 and M11 were clearly visible.

In other parts of the sky, it is notable that an elusive object such as M33 is always easy, whereas M31 in binoculars is a huge object covering about 3 degrees.  It is just perceivable to the naked eye, a feat which I never achieved in Coventry.

One day I might have a go at M69 and M70 but this will mean an expedition to Goonhilly downs on a very dark night to get the necessary S dec.!

Observations with 216 mm   (Sept 13th 21h)

Jupiter much better placed than last year, and the contrast in the sky compared with N. Warwickshire is noticeably greater. The SEB is partly double, both polar regions conspicuous, N might be slightly darker than S.  Irregularities on S margin of NEB.  Both STB AND NTB are visible; I think the UTB is more conspicuous than last year.

M27 'Dumbell' stands magnification well - outline is like the photographs you see in books which is more than can be said for visual observation of most deep sky objects!

M22 Sgr a marvellous sight with many stars resolved.

M8 Sgr getting rather late in the year for this but dark lane across the nebula visible.  Open cluster within one degree.