As did I. Not everyone captured the effect, but it can be captured on
film. SWAG: an atmospheric effect?


I saw a lecture that stated that the effect was due to blurring caused
by a combination of diffraction effects and terrestrial atmospheric
turbulence, these are apparently exarcebated in small aperture
telescopes. A demonstration showed a white circle on a black background
approaching a white edge for different spacings (5..1 pixels)and
different applications of gaussian blur (using Photoshop or similar).
This produced an effect very like images of the black-drop effect.

--
J Whitby