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bluechip
03-20-2010, 08:57 AM
I'm lucky enough to have squeezed out a 120' shooting area in my heated shop. Shooting is a little like threading a needle though. Expensive equiptment within a foot or so from a centerfire bullet on it's way to target. Here's the problem, fluorescents 'strobe' and completely screw up the chrono. I tried putting an incandesant bulb over the chrono, but no go. The entire building is flouorescent, so what's the fix?

blades
03-20-2010, 09:11 AM
Try adding a diffuser over the eyes, Milk white thin plastic or even white typing paper. You have to extend far enough on both sides of each eye to prevent the pick up of the strobe effect from the florescent tubes. You might also have to add some additional light on top / over the diffuser to get enough contrast. I use a chrony in the shop so it is very easy to do above because of its short spacing.

cris
03-20-2010, 10:22 AM
A different chrono.

ShadowChaser
03-20-2010, 10:38 AM
I use a CED M2 with the IR lighting option and even with that, I've learned to shield the sensors from the light from fluorescent fixtures in order for it to work consistently. Its been my experience that any light from a florescent bulb hitting the sensors will cause it to read erroneously...

Gene Beggs
03-20-2010, 10:39 AM
Oehler makes an indoor, incandescent light kit for their 35 and 35P, which I use in the tunnel. It works great!

You didn't mention what kind of chrono you have.

Gene Beggs

Bill Wynne
03-20-2010, 10:42 AM
I have used a incandescent clip on trouble light with my chronograph in my building with good results. I have found that it takes a good amount of direct light on the bullet through the chronograph. If your fluorescent lights interfere with your chronograph, try turning them off.

Concho Bill

mks
03-20-2010, 12:29 PM
Has anyone tried battery-powered LED light sticks? Just wondering if these could solve the indoor problem, as well as low light problems outdoors where electricity isn't available.

Thanks,
Keith

juice
03-20-2010, 01:52 PM
If I recall correctly, the IPSC guys used to put a chrono with the factory supplied light bars in a light tight box. The thinking was that it would lead to consistent results and not be affected by clouds or varying sunlight conditions. Perhaps a variation of this would be useful to you. I hope this helps.
j

bluechip
03-20-2010, 03:05 PM
The brand is ProChrono. I always thought that the bullet interupted the incoming light somehow, but are you telling me that the chrono would actually work in the dark? I guess either way, it's easy to try it with the fluorescents off. Even with all the lights off, I could still easily see the halogen lit target.

abintx
03-20-2010, 03:30 PM
I'm lucky enough to have squeezed out a 120' shooting area in my heated shop. Shooting is a little like threading a needle though. Expensive equiptment within a foot or so from a centerfire bullet on it's way to target. Here's the problem, fluorescents 'strobe' and completely screw up the chrono. I tried putting an incandesant bulb over the chrono, but no go. The entire building is flouorescent, so what's the fix?

My User's Manual instructions for the Chrony models Alpha and Alpha Master say to 1) add the special end pieces [extenders] to the Poly-Diffuser, 2) TURN OFF all halogen and fluorescent lights directly above the Chrony, and 3) Bolt the INDOOR LIGHT FIXTURE ASSEMBLY to the top of the Poly-Diffuser.

In other words, their fix is to bolt a special light fixture assembly with TUBULAR light bulbs ... 40-Watts Frosted ... available from GE as an IMMEDIATE source attached directly to and above the diffuser. It works on 115V house current and OVERPOWERS any other light source in the same room. Neon or other fluorescent lights cannot be used as a Chronograph light source, because they FLICKER at twice the AC power frequency, and cause false readings.

Here's the link for the manual: http://www.shootingchrony.com/manual_ASC&AMC.htm. A picture of the fixture is about 2/3rds of the way down the page. Hope this helps. Art :)

Bill Wynne
03-20-2010, 05:40 PM
User's Manual instructions for the Chrony models Alpha and Alpha Master say to 1) add the special end pieces [extenders] to the Poly-Diffuser, 2) TURN OFF all halogen and fluorescent lights directly above the Chrony, and 3) Bolt the INDOOR LIGHT FIXTURE ASSEMBLY to the top of the Poly-Diffuser.

In other words, their fix is to bolt a special light fixture assembly with TUBULAR light bulbs ... 40-Watts Frosted ... available from GE as an IMMEDIATE source attached directly to and above the diffuser. It works on 115V house current and OVERPOWERS any other light source in the same room. Neon or other fluorescent lights cannot be used as a Chronograph light source, because they FLICKER at twice the AC power frequency, and cause false readings.

Here's the link for the manual: http://www.shootingchrony.com/manual_ASC&AMC.htm. A picture of the fixture is about 2/3rds of the way down the page. Hope this helps. Art :)

That makes sense. Thanks.

Concho Bill

Dennis Sorensen
03-20-2010, 05:50 PM
I think the easiest thing would be to hang a few light bulbs and turn the florescent lights off...

Louis Boyd
03-21-2010, 11:42 AM
Incandescent lights flicker too at a 120 Hz rate but not as high of amplitude as fluorescent bulbs. Larger wattage incandescent bulbs flicker less (in percent amplitude) than low wattage ones. All fluorescent bulbs use either an electronic pulse modulated ballast or a magnetic current limiting ballast. Both produce lots of high frequency high amplitude light variation. It's possible to run a fluorescent bulb on regulated DC current which will give a flicker free output, but I've never seen a commercial lamp driver built to do that.

Automotive incandescent bulbs run off of a battery or regulated DC supply will be flicker free as will LEDs run off of a clean DC source. Some LED lamp drivers use pulse modulation to improve the efficiency and they would be the worst of all as they have 100% modulation at high frequencies. A battery and current limiting resistor is the simplest and least expensive way to get a ripple free light source from LED.

The human eye can't easily detect flicker in a light source above about 30 hz. Light variations in the 10 to 100 kHz range are worst for chronographs. A 1" long bullet at 3000 fps produces about a 50 microsecond dip in the light and it's only a few percent drop in the light level. Sunlight is quite stable at short time scales in comparison to any but DC powered artificial lamps. Most chronographs are built to work in direct sunlight and and require bright light to work properly. Sunlight is much brighter than typical room lighting.

It's important that the width (in the direction of bullet travel) of the light source is narrower than the length of the bullet to get the best output signal. The sunscreens mounted over a chronograph purpose is to produce a uniform illumination above the detector. The detector is usually equipped with a small cylindrical lens which gives it a fan shaped sensitive area. Some chronographs use two mirrors and a laser bouncing many times in a fine spaced pattern before the light reaches the sensor. The advantage is that the bullet cutting any part of the beam gives a strong output. Those don't require external light at all, but the laser and mirrors add cost.

Muzzle blast can also trigger a chronograph. Even though the air is clear the change in refraction from the highly compressed air can produce a pulse as strong or stronger than the small area of light the bullet blocks. The chronograph will measure the pulse which crosses its sensing threshold first, not necessarily the pulse which is strongest. For most high velocity rifles the bullet will arrive first with only a few feet of spacing required to the first screen. That's not the case with some pistols or subsonic rifles where the shockwave will arrive before the bullet at a considerable distance resulting in incorrect velocity measurement.

alinwa
03-22-2010, 12:30 AM
My User's Manual instructions for the Chrony models Alpha and Alpha Master say to 1) add the special end pieces [extenders] to the Poly-Diffuser, 2) TURN OFF all halogen and fluorescent lights directly above the Chrony, and 3) Bolt the INDOOR LIGHT FIXTURE ASSEMBLY to the top of the Poly-Diffuser.

In other words, their fix is to bolt a special light fixture assembly with TUBULAR light bulbs ... 40-Watts Frosted ... available from GE as an IMMEDIATE source attached directly to and above the diffuser. It works on 115V house current and OVERPOWERS any other light source in the same room. Neon or other fluorescent lights cannot be used as a Chronograph light source, because they FLICKER at twice the AC power frequency, and cause false readings.

Here's the link for the manual: http://www.shootingchrony.com/manual_ASC&AMC.htm. A picture of the fixture is about 2/3rds of the way down the page. Hope this helps. Art :)

I bought 8 bulbs and cheap "trouble light" fixtures at Lowe's for less than the price of a set of these lights, same bulb. They work great.

al

mks
03-22-2010, 01:10 PM
Louis,
Would a cordless LED trouble light like this be pulse modulated?

http://www.amazon.com/Super-Bright-Rechargeable-Cordless-Light/dp/B000JN6ZYS

Thanks,
Keith