Gentlemen &/or ladies,

I know we have some sharp minds frequenting this forum, so I am sure this is the place to ask this question. Can anyone explain for me(in as much detail as possible, without unduly taxing yourselves) exactly how a chronograph works? (ie. what is measured, how its measured, what components are used, and the influence of "conditions" )

I understand the basics, but am looking to improve my understanding of the finer details(to help with trouble-shooting, etc).

Thanks in advance to anyone that can help.

Canuck

[This message has been edited by Canuck (edited 04-25-2001).]

Canuck - Nothing too mysterious here. A chronograph is simply a very accurate timer. The guts of all choros are basically the same 1. A clock, and an optical device that activates the start and stop of the clock. The chrono measures the time it takes for an object (bullet) to cross a measured distance and then calculates it's velocity. As you can imagine, this process must literally take place in thousands of second. The more accurate the clock, the more accurate the measurement.

The gage in which chronographs are measured is by the quality of the start/stop optics. The optics depend upon sufficient lighting to register the bullet passing over the eye. Too bright or too dim and the optics cannot �see� the bullet. Most chronos offer the same basic features. However, in my opinion, Oehler makes the best equipment hands down.

The reason why I like the Oehler chronographs so much is that they include two stop screens. One at two feet and one and four feet. This provides a backup or �proof screen� which indicates any abnormal measurement. In addition, they have the best optics in the industry. Oehler has been a leader in the chronograph industry for many years and their equipment is used extensively in the laboratory and for military applications.

If you are a hand loader, a chronograph is necessary equipment. It is one of the best ways to ensure accuracy and consistency.

Z

[This message has been edited by Zero Drift (edited 04-24-2001).]

Thanks Zero. Can you explain what triggers the eye to register the bullet passing overhead?

I guess what I am trying to figure out is how filters, screens and lights can influence a reading. Also, what effect different size projectiles (bullet vs arrow) might have on accuracy of a reading.

Thanks again,

Canuck

The chrono optic eye picks up the shadow of the bullet as it passes over the eye. As I mentioned, some chronos are very finicky when it comes to lighting. Most come with sky screens to help diffuse direct sun light. A lot of guys with other chronographs waste time and ammo during marginal lighting conditions. My Oehler does not seem to care what type of light you feed it as long as it is not fluorescent lighting.

The size of the projectile does not matter as long as the eye can see the projectile. I have shot a pellet gun across mine with no problems. There is a setting on the Oehler that is designed to read slower objects like arrows, pellets, and even shotguns.

The muzzle blast of larger caliber guns can cause an error. The shock wave actually creates a shadow of sorts (the pressure wave bends light) which activates the start screen. In this case, you will need to move the screens further away from the muzzle. Other than that, you should always get accurate readings.

Z

[This message has been edited by Zero Drift (edited 04-25-2001).]