RE: Slowest STW known to man
I use one quite often and usually set it up 10-12 feet away. I don't even know it is there now.
This is from their manual:
4. To safeguard the instrument (and to obtain the best results), the projectile must pass between 6 and 4 inches (15 and 10 cm) directly OVER the Twin Lenses in the black plastic boxes at the front and back of the chronograph. These are the chronograph’s "eyes". Attaching pieces of dark-coloured tape on the guide rods (wire rods) at these heights, will help you to accurately aim your shots.
5. The Shooting Area. Every Shooting Chrony and Master Chrony comes equipped with an adjustable-size, triangular shooting area (actually an upside down trapezium) from 8"X8" to 14.5"X14.5" (Fig. 2). All Chronys come equipped with four 9.25" wire rods as well as four 6.5" wire rods with brass connectors attached. The 9.25" wire rods are to be inserted at an angle into the outer holes visible on the black plastic boxes of the unit. On bright, sunny (blue sky) days, install the white plastic diffusers on top of the wire rods (to simulate clouds). The photo-sensors are pointed at the diffusers, which create a white background (clouds or diffusers). On cloudy days, use wire rods for alignment, but without the diffusers.
6. Chronographs should be at least 10 feet (3 m) from the muzzle of a high-powered rifle, but can be closer to guns with a lesser blast. Five feet (1.5 m) is about right for .22 rimfire firearms. Shotguns should be fired at 5 feet because of the spreading pattern of the shot and errant wads. Arrows must be clear of the bowstring before passing over the first "eye".
Hope this helps