PROCHRONO LTD
U S E R M A N UA L / O P E R AT I N G I N S T R U C T I O N S
4
Some Common Conditions that May
Cause Problems
You can encounter a wide variety of lighting conditions if you use your
chronograph outside. The following are some things to look out for:
Reflections
On sunny days, reflective projectiles may cause “glints” which can induce velocity
errors. This phenomenon is minimized by using the diffuser hoods. However,
depending on the position of the sun, further setup adjustments may be
necessary. If false readings occur with the diffuser hoods in place, you can correct
the problem with one or more of the following steps:
• Change the position of the chronograph relative to the angle of the sun
• Color the bullet tip with a black, permanent marker
• Move the chronograph to a location in the field of a shadow cast by a building
or an opaque wall. Make sure the sensors have a clear view of the sky but the
chronograph itself is within the shadow. An alternate method for this is to
use shields taped on the sides of the guide rods to create the shadow. Be sure
to use cardboard or something similar that will not cause any problems with
ricochets. This will eliminate reflections from direct sunlight, while still assuring
that the chronograph has a direct view of the sky. In some cases, doing this
may reduce the incoming light level too much and make the chronograph less
sensitive
Trees
You should not locate your chronograph in the shadow of a tree since the
movement of leaves and branches can cause instability in the lighting
environment.
Sunrise and Sunset
The lighting conditions at sunrise and sunset can cause errors due to reflections
(glints), skewed shadows, or low light levels because of the extremely low angle of
the sun.
