2012-03-02 48 12
Next to a road in the Laber valley, a few kilometers west of Regensburg.
Another of those "too close not to go" hashes that I somehow missed at hash o'clock the previous day. When I noticed it during breakfast, I planned to go there in the evening after work. There had been a clear sky for most of the day, but after sunset a rather dense fog built up. I cycled home from the office through said fog, had dinner, procrastinated for a while and then left for the hash at something like 23:15, knowing it would only be a ride of about five or six kilometers, and mostly on well-known and easy terrain, including a stretch of former railroad converted to a cycleway.
I had assumed I had been to this place before, remembering a bike trip to some geocaches on a summer day - but I was wrong, that trip was in an entirely different valley. However, ekorren and I had passed precisely through this point by bus on our way to 2011-04-06 48 11!
Anyway... I got there, parked my bike at a tree and a sign advertising a parking/picnic area, GPS-danced down the slope next to the road and located the spot on a small grassy strip, beyond which there would have been a very muddy field. After snapping the photo of the GPS, I moved to the parking area to take a couple of pictures of passing cars. I ended up staying on that spot for nearly an hour before cycling back home, because there was Science to do!
Namely, after fiddling with camera settings for some time, I managed to take pictures of an optical phenomenon I had noticed previously while cycling through dense fog next to a road: when a car passing me from behind was something like 100 meters away, a circular arc of light would appear in the fog before me, stationary (relative to me) and not changing its apparent size, until the car was maybe 30 meters behind me and the direct light from the headlights started to dominate and wash out the scene.
This phenomenon lasts only for about two seconds (obviously depending on the car's speed) and, it seems to me, can't be seen by the car driver themselves. And who would ever park their car in dense fog, turn on their upper beam headlights, and then get out and walk off into the beam?
The inner edge of the arc is blueish and the outer edge is reddish, so I assume it technically is a rainbow, although it looks so much "closer" that it looks larger than the 42 degree arc one would expect there. The only lenses I have that are fast enough to capture the phenomenon (one second at ISO 800 with a f/1.7 aperture is just about right) are too long to capture the full arc, so I can't really say what angle it covers.
Anyway, finally I managed to photograph it so I know I wasn't hallucinating :-)