Chronographs and light
by B.B. Pelletier
Those of us in the Northern Hemisphere have a trying time using our chronographs in the winter. When you get home from work, the daylight is gone, so some kind of artificial lighting is needed for the skyscreens of most chronographs. This can be a problem unless you know a few things.
Fluorescents HATE chronographs...
...but they LOVE skyscreens! Fluorescent lights will trigger your skyscreens without any intervention from you. Even if you have incandescent lighting directly over your skyscreens, a nearby fluorescent light will set off the screens, giving you a false reading on the chronograph screen. Skyscreens work on intervals of light and dark, and a fluorescent light pulses at just the right cadence to set them off.
Shop lighting not much better
The powerful vapor-type lights used in industrial shops and warehouses these days are almost as bad as fluorescent lights at setting off skyscreens, however I have found it possible to override them with good local incandescent lighting, such as the Chrony Skyscreen Lights that are the No. 1 option for anyone who owns a Chrony. You can also make your own light bar with regular incandescent lights, if you like. Space them to shine down on each skyscreen. They should be low wattage - between 15 and 40 watts. You can even use these lights in a room by themselves, so turn off those other bad lights!
Okay, the weekend arrives and you can finally use that Chrony Alpha outside - or can you? For some reason, your skyscreens are still triggering and giving false readings, despite being outdoors in daylight. What gives? Two things - bright sky with rapidly moving clouds, or it's breezy and nearby trees are casting moving shadows on the screens. Either one of these conditions will set off any chronograph's skyscreens.
When you go outdoors, you want either an overcast sky or a blue sky with the sun not shining directly on the screens. If there are clouds, they shouldn't be moving about, causing sudden shadows. Stay away from trees, because of the moving shadow problem. If you use a tripod for your chronograph, remember that you can always angle the skyscreens toward a better part of the sky. Read Tom Gaylord's article about chronographs for other tips.
Using the skyscreen diffusers
All chronographs come with light diffusers that can improve lighting during difficult times. Most of the time you don't need to attach the diffusers, but under some conditions they're the only things that work. I assume you've read the article linked above and have seen what diffusers look like. They are for use on extremely bright days when the sun is almost directly over the skyscreens. Direct sunlight overpowers the sensors, making it impossible for them to "see" the faint shadow cast by a pellet speeding by. Think of diffusers as sunglasses for the chronograph. My trick of tilting the tripod also works in this situation, and I find it easier. If all you have is a flat table for the Chrony, use the diffusers.
Diffusers also help on a breezy day when sun and shadows are moving fast, though sometimes nothing works very well on those days.
Chronographs are wonderful measurement tools that can add a lot of enjoyment to anyone's airgunning experience, but they do require some understanding. Learn to use your chronograph so you can be confident that the numbers it gives are correct.