chrony and sun/overcast

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by älg, Sep 14, 2007.

  1. älg

    älg Well-Known Member

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    I wonder if you see a big difference in read velocities when using the crony in a sunny day and then clouds/no direct sunlight??

    I was testing some velocities today, first shot with sun 3120, second shot there was a big cloud, 2890 ??? same load, same bullet, weighed cases....

    do you experience such a big influence, or it´s pribably my crony ?

    thanks.
     
  2. J E Custom

    J E Custom Well-Known Member

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    All Chronographs need good light to work properly

    I use the ohler 35 p with the proof screen ( 3 screens )
    and when i'm in poor light it sometimes gives me an error
    warning so I edit that shot.

    Chances are thats what is happening to you with that much
    velocity spread.

    Or if your shooting less than 6' to 8' from the chrony the shock
    wave from the muzzel blast can cause erratic readings.

    I hope this helps
    J E CUSTOM
     
  3. dbhostler

    dbhostler Well-Known Member

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    Cloudly days are actually brighter than clear days. You have a better chance of getting a no start or stop signal on a clear cloudless day.
    db
     
  4. royinidaho

    royinidaho Writers Guild

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    I've "noticed" that cloudy days are much better for the Chrony than bright sunny days.

    Bright vs cloud makes a difference in readings. That much of a difference is unusual in my experience.
     
  5. älg

    älg Well-Known Member

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    Thanks for the answers. I agree that is way too much difference to be caused just by the clouds.-will check the crony with another unit.
     
  6. Ahab

    Ahab Well-Known Member

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    Fast moving clouds can also effect your reading.
     
  7. specweldtom

    specweldtom Well-Known Member

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    I haven't used a Chrony, does it have a diffuser above the eye? As DB and Roy said, bright clear sunlight makes it harder for the chronograph to "see" the bullet, and the Oehler skyscreen III's have a big translucent orange diffuser above each eye to stop the glare.

    Unless the processor in the chrono is screwing up, I'd suspect extreme spread on the load. I don't know if the shock wave could rock the screens enough to cause that much deviation without just failing to read. Best I can recall, shock waves, when they read, show around 1300 fps. I set my 1st screen about 7-8 yds. Makes a smaller window to shoot through, but stops most errors. I've never thought about a clear or cloudy day making a difference in the readings. I just figured it would read if it had enough light and wouldn't if it didn't. Another addition to the huge list of stuff that I don't know.

    I'd like to know what happens when you make the comparisons.

    Thanks, Tom