The Journal of the British Astronomical Association

Volume 108, No.5: 1998 October

List of Contents

Notes and News

(Woodcut of the constellation Leo by Albrecht Durer, 1515)

Articles

A classification of auroral types ... D. A. R. Simmons

All the currently recognised auroral types have been drawn together in a single classification based on their geophysical characteristics. A brief portrait of the most typical features of each type is presented with special reference to geomagnetic latitude, geomagnetic time sector and mechanism of aurora production. These and other characteristics make it possible to compare and contrast the similarities and differences between the different types of aurora on a geophysical basis. (11 pp, colour photographs)

This paper describes the most effective ways in which the ordinary citizen can use the legal and planning systems to minimise inconvenience and damage from unwanted light. (3 pp)

This paper reports rapid changes in the distribution of bright white patches in one region of Io, close to the subjovian point and the caldera Karei Patera. A stable pattern of white patches in this region was recorded by Voyager in 1979. A strikingly different pattern was shown in the first Galileo-G1 image (1996 June). However, the patterns in another Galileo-G1 and several Galileo-G2 images (1996 September) were similar although not identical to that seen by Voyager. Hubble Space Telescope images in 1994 and 1995 also resembled the Voyager pattern. The changes in the first Galileo image are not easily attributable to differences in lighting and viewing angles, and appear to be real physical changes, which occurred over a matter of days during the Galileo-G1 encounter. They also do not have the characteristics expected of surface deposits. I suggest that some of these white patches may be drifting opaque white clouds. They may be emitted from volcanic sources which have recently been reported in this area. (4 pp, colour images)

A focusing mount with the ability to take a range of government surplus eyepieces was required for a home-made 60mm refractor. After considering machining one from brass bar/tube an almost ready-made solution was found. (1 pp)

Seeds, insects, birds, pollen, snow and hail have all puzzled telescopic observers in the past with apparently strange apparitions. Richard Baum describes some of the observations that have found their way into the literature. (2 pp)

Letters

• Solar Fraunhofer lines with a diffraction grating ... Brian Manning
  
• Aircraft condensation trails ... Michael Hendrie
  
• The Sky at Night ... Pieter Morpurgo
  
• Amateur spectroscopy ... Gerald North
  
• Solar eclipses at a given place ... Jean Meeus
  
• Pluto - the ninth planet ... Martin Ratcliffe
  

Reviews

Meeting reports

• Ordinary Meeting, 1998 May 27
  

BAA Update

• Obituary: E. W. P. Turner, 1928-1998
• Meeting of the Instruments and Imaging Section, 1998 May 30