British Astronomical Association
Supporting amateur astronomers since 1890

Secondary menu

Main menu

BAA Gallery Picture of the Week
Image search

Venusian Green Flash


Expand image

About this observation
Pete Lawrence
Time of observation
16/10/2019 - 18:15
Observing location
Leicester, UK
Canon 6D DSLR, Sigma 50 - 500 telephoto lens set at 500mm focal length
1/64s exposure @ ISO 2000 with the lens aperture set at f/8
Like This Image

Pete reports that, following a beautifully clear day he attempted to get an early view of Venus low above the south west horizon after sunset. Although the planet wasn’t visible to the naked eye on this occasion it was an easy binocular target. It also stood out fairly well in a number of photographs he had taken as the planet approached the horizon. Having photographed the sunset earlier, he noted that there was plenty of green visible along the northern edge of the Sun, an effect caused by atmospheric dispersion. The thought occurred as to whether it would be possible to capture the atmospheric dispersion of Venus at this time as well. The effect was present as Venus got lower but was small and heavily affected by atmospheric seeing. The best way to catch it would be to use video, but as Venus headed for the horizon, the equipment was set up for stills and so he decided to try his luck. The appearance in this image lasted for a fraction of a second, "seeing" having destroyed the effect both before and after this shot. It shows an almost perfect dispersion of the light of Venus through Earth’s atmosphere with red at the bottom and green at the top. The blue component, which should be there has been scattered away. The pylons in this shot are roughly 1.3 miles away, the tree line 1 mile. The horizon is virtually perfect in that it is around zero degrees altitude. Being able to capture this fleeting glimpse of an atmospheric phenomenon is very special.

Copyright of all images and other observations submitted to the BAA remains with the owner of the work. Reproduction of the work by third-parties is expressly forbidden without the consent of the copyright holder. For more information, please contact the webmaster.