Ich hab mal aus Neugier genauer gelesen, und meine, es könnte tatsächlich Streulicht sein. Einmal gibt's Zubehör, mit dem die Streifen beleuchtet werden:
"INDOOR USE
"For proper functioning, a light-diffuser and an incandescent light source must be located above each photo-sensor window (Fig. 5). The Optional Indoor Shooting Light Fixture enables owners of the Chrony to pursue indoor use. Neon or other fluorescent lights cannot be used as a chronograph light source because they flicker at twice the AC (alternating current) frequency and cause false readings."
Und:
"On sunny days, at certain angles, light may reflect from the bullet and cancel the bullet?s shadow. Mark the bullets all the way around with a dark-coloured felt marker if this seems to be happening.
"On sunny days, the Chrony may be tilted sideways toward the sun, so that the Diffusers are between the sun and the photocells. Be sure that the Chrony unit remains fully open, and that it is perfectly aligned with the target. Using diffusers on cloudy days may shut out too much light.
"Using diffusers on cloudy days is not necessary, since you have the clouds as a white background for contrast."
Ich hätte ja auch auf eine Lichtquelle im Gerät getippt, die die Streifen beleuchtet, aber die Wolken wird die ja nicht beleuchten...
Thomas Prufer