Black drop at third contact (egress), Transit of Venus, Athens, Greece, 2012
Transit of Venus taken from Philopappou Hill in Athens. Venus sits at the top, not quite at third contact (egress) but the black drop is most definitely there, as seen in the inset top right... There is also some spectacular lens-flare off the seventies optics!
The image was captured on a Nikon D3100, unfiltered, with shutter and ISO as per EXIF and with an aperture at around f/22 (smallest available). The lens is a 300mm Nikkor H, with a 2X Kenko non-AI Teleconverter in series with a Kenko 3X non-AI Teleconverter to give an effective focal length of about 1800mm. The image has been slightly processed for levels, tagged and re-sized to half size in GIMP.