Chrono PLUS Sunshine EQUALS errors???


January 18, 2010, 10:43 AM
Saturday I was checking some velocities with my new Alpha master Shooting Chrony and the overcast skies gradually opened up to sunny.

Per the directions re overcast I was shooting without the diffusers. Obviously the overcast to sunny transformation was a gradual one, BUT...

When I switched to the diffusers, my velocity measurements dropped 1-200 fps!?!?!?!?\

I have on order a LED light and battery pack for low light conditions, but Has anyone ever dealt with this phenomenon before?

Do ya'll just leave the diffusers over the sensors all the time?

Thanks for input!

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January 18, 2010, 10:47 AM
Yes, leave the diffusers on.

I have had problems when the sun's angle is such that direct light reaches the sensors even when the diffusers are on. Then velocities are all messed up.

If you can test in the shade it will work better. Overcast is great, sunlight and blue skies are bad.

January 18, 2010, 11:06 AM
Yep. It's been on this forum a half dozen times in the last couple years. But it's easy to miss while surfing forums. However, the error of direct sun on the sensor is generally rather large, not just 100 to 200 fps. Are you sure those numbers aren't accurate? Maybe they are...

Got an extra target stand? Set it next to the chrono and orient it so the chrono box stays in the shade of the target. Keep the screens on. Stay 10 to 15 feet back so muzzle blast doesn't affect the readings.

To quote a guy on another forum, "I have confidence that my chrono will never shoot me, but the feeling isn't mutual."

January 18, 2010, 11:21 AM
The sun wasn't directly into the sensors, but it was brighter than overcast... perhaps partly cloudy, (like an upper level thin cloud cover...)

I may try the shade thing...

The quote is Great!

Sorry for bringing up old info. I've only had the chrono 1 month and had I read this info before that I would've ignored it anyway!


January 18, 2010, 11:52 AM
OK, I understand. Sun shining directly into the diffusers makes big errors. Absent sky screens gave you small errors. That makes sense. What brand of chrono do you have?

January 18, 2010, 12:03 PM
I switched to IR screens a few years ago. Sun or shade doesn't matter.

January 18, 2010, 01:40 PM
Shooting Chrony Alpha Master Chronograph (red)

January 18, 2010, 02:08 PM
Any chance you can get your $$$ back? I don't say this to be smart alecky; only that after having two Shooting Chrony's (F1, F1 Master), life is SO much better with a Pro Chrono Digital. No more light errors in any reasonable conditions, no more 3" diamter pipe shooting area without an err message, no crazy readings, no missed shots, and no more inaccurate (read fast) readings.

Yep, they were set up right, fresh batteries, 15-20 feet in front, fully opened, diffusers... By contrast, turn on the PCD, shoot through the huge area and get reliable results, Period. PCD has a very similar 1/2 retail price for a new one when you shoot it, and I hope unlike SC they actually honor their warranty should I need it unlike SC did with me. I truly say this like a friend who doesn't want to see a person get screwed as per my experience, which is all anyone can do.

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