Thomas:
Ditto on the cardboard. You want the space between the two diffusers shaded so there is no "cross talk" from the light. I use mine mostly indoors and have the F1 Chrony at bookshelf height, about 3 ft from the ceiling. I use a halogen desk lamp and instead of aiming it toward the diffusers, I shine it on the white ceiling above the diffusers and turn out any other overhead lights in the room. I take a 3-ft section of 1x6 board and set one of Timmy's large pellet traps on the end of the board on the bookshelf, and then I clamp my Chrony on the board about 2 ft in front of the pellet trap. I put a target on the trap centered about 6 inches above the sensors. When I shoot, I stand back about 5 ft from the Chrony, set the AO on the scope to the shortest distance, put the cross-hairs on the bull, and take care to make sure that the vertical reticle lines up with the sensors on the Chrony and that the "V's" made by the small rods holding the diffusers are aligned symmetrically front and back, in the scope's sight picture. At that range, the POI is lower than the POA and the pellet passes about 4-5 inches above the sensors. That way, it doesn't shoot up the bull on the target and I have a consistent POA to shoot at, standing. Seems to be pretty consistent. I occasionally check the set up with my SPP Beeman P3. It is a consistent 410 FPS with RWS Hobby, and I can check the Chrony's readings for accuracy with it.
