J. Brit. Astron. Assoc., 108, 3, 1998, p.136

Letters

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The Leonids from Cambridge in 1799

From Dr Jeffrey C. Barham

I have recently spent some time in the Cambridge Central Library going through old local newspapers (The Cambridge Chronicle and The Cambridgeshire Independent Press) and copying references of astronomical significance. I placed a copy of these in the University Institute of Astronomy and Dr.David Dewhirst of the Institute suggested that the item for 23rd November 1799 might be worth publishing. The Cambridge Chronicle came out on a Friday, so 'Tuesday se'nnight' would be 13th November 1799. Dr Dewhirst said that he couldn't remember having seen an account from England of what is clearly the famous Leonid shower of that year. So this account is rare, and possibly unique:

From the Cambridge Chronicle, 23 November 1799:

'On the morning of Tuesday se'nnight, between the hours of five and six, the heavens exhibited an awfully grand appearance. The Moon became partially obscured by dark cloudy spots or streaks – In opposition to her was seen a lunar rainbow of the most beautifully varied colours – after which the middle region of the air was illuminated by meteors, crossing each other in different directions, and leaving behind them long sparkling trains, which were visible for two or three minutes after these luminous bodies had disappeared – One of these meteors, more brilliant than the rest, illuminated the whole firmament, and by its apparent approximation to the Earth created some alarm in the minds·of the beholders, who all declared that they never witnessed so sublime a scene...'

Jeffrey Barham
76 Wimpole Road, Barton, Cambridge CB3 7AD

Frequency of eclipses in the British Isles

From Mr Peter Macdonald

The approach of the total eclipse in 1999 prompts questions regarding the frequency of eclipses in the British Isles. Some while ago, I investigated the circumstances of eclipses occurring at London between 1951 and 2100.[1] I found that 62 solar eclipses and 132 lunar eclipses are visible. Penumbral lunar eclipses were not taken into consideration since they are barely distinguishable to the naked eye and are of no interest to the casual observer. This total of 194 eclipses – an average of more than one a year – gives a frequency far greater than one would expect. However, many take place close to the horizon and are practically invisible.

During this period, the capital does not experience a total or annular solar eclipse, although five attain a magnitude greater than 0.90. These occur on 1961 February 15, 1999 August 11, 2026 August 12, 2081 September 3 and 2090 September 23. Total lunar eclipses are visible on several occasions. Total solar eclipses are visible from some part of the British Isles on 1954 June 30, 1999 August 11 and 2090 September 23, as are annular solar eclipses on 2003 May 31 and 2093 July 23.

For the general public an eclipse must be noticeable. Popular eclipses are likely to be limited to solar eclipses having an appreciable magnitude and occurring with the sun well above the horizon, and lunar eclipses taking place before midnight. Many will have recollections of, perhaps, just one or two striking eclipses, giving the impression that they occur infrequently. In recent years the total lunar eclipse of 1992 December 9 and the partial solar eclipse of 1996 October 12 have been particularly favourable. The frequency is demonstrated in the table which lists forthcoming eclipses until 2015.

[1] Macdonald P., Eclipses at London 1951–2100, private publication, 1994

Peter Macdonald
46 Vista Way, Harrow, Middlesex, HA3 OSL

Aircraft condensation trails

From Mr John Vetterlein

In response to my brief reference to aircraft condensation trails (Newsletter No. 87), Cliff Meredith states (Newsletter No. 88), 'The first 'official mention' I can recall about vapour trails seriously affecting astronomical observing was made by Andy Hollis (now Dr Hollis) during his BAA lecture about asteroid photometry, given at Lancaster University three or four years ago.' Of course it depends on our interpretation of 'official mention'. I can recall saying something about it to a bunch of Cambridge graduates and undergraduates as far back as 1957.

My experience for some time now – at least fifteen years – has been that you are indeed fortunate if such artificial clouds do not mar your view of the sky, day or night. We are all guilty, no doubt. Astronomers themselves are quite happy to take a flight to observe an eclipse, or to make off to some distant land for a glimpse of a comet or what have you. Where light pollution is concerned we may improve matters. With the condensation trails it is a question of taking to heart the maxim: 'Journeying through the mind is the art of staying put.'

John Vetterlein
Springfield, Rousay, Orkney KW17 2PR

Solar Eclipse 1999 – Plymouth

From Mr Tom Wildy

I note from the Internet search results at Yahoo that your Eclipse link refers only to Cornwall. There will, of course, be about 2 minutes of totality in Plymouth, and the place to be is the historic Hoe. The Eclipse will occur between the British Fireworks Competition (the only one in the country) and the annual summer music festival Soundwaves.

A week in Plymouth at this time is much sought after, and I, for one, would not try to move into Cornwall, where narrow roads and too much traffic are likely to gridlock the county. I would be grateful if you could make it clear in mentions that the Eclipse does not magically jump from the Tamar to the coast of France!

Tom Wildy
11 Napier Street, Plymouth PL1 4QX [Tom.Wildy@btinternet.com]

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