The Journal of the British Astronomical Association

Volume 116, No.3: 2006 June

Detailed contents: Notes and News / Articles / Observers' Forum / Reviews / Letters / Meetings / BAA Update

On the cover: 2006-03-29: 'The eclipse with everything'

The total solar eclipse of 2006 March 29 was the first for many years to be observed in cloudless weather conditions for almost the whole of its track. This composite image of the corona was taken by Mark Winpenny with the Explorers Tours group south of Jalu in Libya, using a Canon 1D Mk II digital SLR with a Canon 300mm f4 IS lens with x1.4 converter (effective focal length 546mm). 25 frames were used for the composite using a slightly modified Pellett method.

Notes and News

'The eclipse with everything' (Hazel McGee) / From the President (Richard Miles ) / Solar Section (Mike Beales) / 2006 BZ8 - a 'sword of Damocles' (Roger Dymock ) / Joy Griffiths, 1942-2006 (an appreciation) (Bob Mizon) / Aurora Section (David Gavine) / Mars in 2005: Second interim report (Richard McKim) / Mercury in colour: an observational challenge (Richard McKim)

Refereed papers

The Rev. William Ludlam (1716-1788) and the Cockfield Tower Observatory ... Martin Mobberley

The life of an eighteenth century astronomer, mathematician and rector, and the surviving evidence of his unique observatory in the tower of a Suffolk church, are described. Get PDF

Planetary and lunar imaging with a webcam ... Martin Morgan-Taylor

This paper outlines the use of the webcam for planetary and lunar imaging, and describes how this new form of imaging can sidestep some of the major problems faced by the traditional film-based observer. The different stages of imaging, from data acquisition to final processing, are introduced and explored. Get PDF

Noctilucent cloud over Britain and Western Europe, 1998-2000... David Gavine

This summary of noctilucent cloud (NLC) sightings in the period 1998-2000 is in the abbreviated form already used in the Journal. Times in UT indicate the limits during which the NLC was seen, not necessarily its duration. Get PDF

Analysis of Venus transit images obtained by long-distance, plane mirror, solar projection... David Airey

It is shown that it is possible to obtain reasonably clear photographic images of a dark ~1' diameter object (Venus) against a ~30' diameter intense light source (the Sun) using a small plane mirror at large mirror/image distance (L). Angular resolution is limited at small mirror diameters (d) by the Rayleigh criterion and at larger diameters by 'geometric' considerations. The best theoretical angular resolution achieved, with L= 21.8m and d= 9mm, using strict geometric arguments is ~85". However, the image analysis indicates a rather smaller (superior) value. An alternative argument based on overlapping intensity distributions (as per the Rayleigh criterion) suggests that the limit at L/d= 1/2400 (the geometric equivalent of conventional lens 'f' number) may approach ~40". Attempts to improve geometric resolution beyond this value are frustrated by the very rapid fall-off in image brightness (as d^2) with decreasing mirror diameter. A simple numerical model has been developed to predict both the FWHM of the shadow, and its central contrast, as functions of the mirror diameter. Reasonable agreement is obtained with the measurements, and the model gives a detailed insight into the transition from umbra to penumbra as the mirror diameter is increased. Get PDF

BAA Update

First BAA observations using the Faulkes Telescope ... Nick James

Obituary: Ronald Nicholas Irving, 1915-2005 ... Christopher Lord

Opening of two 'Victorian' observatories ... John Armitage

Reviews

Comets II by Michael C. Festou, Uwe Keller & Harold A. Weaver (Eds.)
University of Arizona Press, 2005. ISBN 0-8165-2450-5. Pp xvii + 745, $85.00 (hbk).

Reviewed by Jonathan Shanklin