MNASSA : Monthly Notes of the Astronomical Society of South Africa

Annual Index, Vol. 77 (2018)

Observation of lunar eclipses by ASSA dates back to the early 1970s. Observations of the total lunar eclipse of 6 August 1971 included nine photographs by N B Dumas (Wild 1971), as well as occultation timings of stars by the eclipsed moon (Muller 1971). These observations said nothing however about the nature of the umbral shadow, which varies from one eclipse to another. The first measurements of umbral geometry, darkness and colour were made during the total lunar eclipse of 24 March 1978 (Cooper 1978) including darkness measurements for the first time using Danjon’s scale, following the excellent article by Sinnott (1975). Since then nearly all lunar eclipses visible from South Africa have been observed to measure the colour and darkness of eclipse, and size and shape of the Earth’s umbral shadow. The techniques used were discussed in Cooper (2004) and Cooper and Geyser (2004).

Circumstances for the latest total lunar eclipse (TLE) on 27 July 2018 were very favourable for South Africa, as the Moon passed close to the centre of the Earth’s shadow with umbral eclipse magnitude M = 1.61, while the altitude of the Moon at mid eclipse was 63° as seen from Johannesburg. This gave the opportunity to conduct measurements without significant interference from a large atmospheric airmass, which would otherwise affect the observed darkness and colour of the eclipse, akin to the effect seen when the moon is rising or setting. Given this opportunity the authors conducted measurements of darkness and colour on this latest eclipse using a variety of techniques. Plans for future observations are presented.

The 13” Refractor at Boyden Observatory, Bloemfontein, has a very special Mars heritage, as it was used by Astronomer William Pickering to capture the first ever photographic images of the red planet in 1888. Due to my specific interest in high resolution imaging of Mars, since discovering this heritage, it has always been an ambition of mine to undertake an imaging run of Mars using this telescope. Although it was my original intent, I was unable to visit Bloemfontein close to Mars opposition in July this year due to an accident earlier in the year which prevented me travelling. However, an opportunity arose in early December, with the University of the Free State(UFS)/Boyden Observatory working closely with ASSA Bloemfontein, myself and the Telescope Shop(Neil and Jess) to co-ordinate an event that incorporated a private showing at Naval Hill planetarium, astro-imaging presentations at Boyden Observatory, a tour of the Observatory and an imaging/observing session on the historic 13” Boyden Refractor as well as other telescopes that had been brought down from Johannesburg by the Telescope shop.