[BAA 00506] Venus: the 2010 E. Elongation

[Rick]

BAA electronic bulletin No. 00506 -- http://www.britastro.org/
Bulletin transmitted on Mon Aug 2 23:34:13 BST 2010
(c) 2010 British Astronomical Association

VENUS: the 2010 E. Elongation

At the present time, as in 2002, 1994, 1986 and 1978 (etc.), Venus is favourably placed for observing its gibbous disk with phase around 0.60. Although the planet is only a few degrees away from greatest elongation, its declination is just north of the celestial equator (as of 2010 late July), and quickly decreasing, so that many observers will find the planet too low to see above the treeline in the evening sky and daylight observation may be called for. Finding the planet with setting circles, the Director recently had several good views around mid-afternoon. If possible, shield the telescope tube from the direct rays of the Sun as otherwise tube currents will spoil the seeing conditions.

We have a fair number of observers making and contributing all-important ultraviolet images, but (ironically) very few visual observers. It is important to continue to monitor the clouds of Venus for any unusual phenomena, so adding to the historical record. The recent bright spot is a case in point: see the 2009 October BAA Journal (119 (5), 240 (2009)). Therefore please try to make drawings of the planet in white light and if possible through the appropriate Wratten colour filters (see the Observing Guide for more details). We require careful sketches to show the apparent phase, a note of the relative size and brightness of the cusps, and positions of bright and dark markings. Timing the moment of apparent half-phase (dichotomy) is important for the purpose of historical comparison: at evening elongation this normally occurs around 5 days early. A large number of such observations made in early to mid-August will be essential for this programme. Phase work is best done visually, because images appropriately exposed for the majority of the illuminated disk will underexpose the terminator.

From phase approx. 0.30 or lower, please examine the planet against the darkening sky to search for extensions of the cusps or the elusive Ashen Light. In 2010 such studies will only be possible from the southern hemisphere due to the planet's high southerly declination towards inferior conjunction.

Report forms can be obtained by post from the Director or downloaded from the Section's website. The webiste has recently been updated by David Arditti and is currently a 'work in progress'.

Richard McKim, Director