The 100 degree heat here for the last month or so has got me into the experimentation mode again to try and find a way to make my Oehler 35 read at night. Temps still aren't exactly cold at night but 75 degrees is better than 100.
The first experimentation was done to try and find a homemade lighting system that would be lightweight and run on batteries. So I looked around and found some Gerber 3 bulb LED headlamps with straps. I attached them to the tops of the orange diffusers shining down through it. This is the classic way of chronographing indoors. The first test showed no readings on the display. So I increased the distance from the bulbs to the diffusers by inserting foam under the lights. This helped spread out the light across the diffuser but substantially decreased the brightness. Perhaps this method would have worked with more bulbs or more brightness, but then weight would increase and the screens might not like that extra weight especially when the wind starts blowing! This is what that looked like:
Then I decided to shine the light up from underneath the screens to the bottom of the diffuser. This method looked cool and was easy to shoot through without being blinded but I got not one reading on the display from this method either. Here is what it looked like:
Next method was to hang the headlamps back up on the diffuser only this time to shine them directly down into the lens itself in effect not using the diffuser at all except for something to hang the light on. To my surprise, this method actually read every single shot from my .357 magnum and about 1 shot out of every 5 from my 6br. This method could possibly work better if I could have stiffened the light source a bit more. In the wind, the lights wiggled a lot from the elastic headband vibrating. Here is what it looks like:
Ok, a call to Ken Oehler was in order. He told me that my first method was the only way it would reliably work, but I needed more light and it needed to be spread across the diffuser more evenly because the lens will focus on the brightest spot automatically and will miss the shadow of the bullet off center. He also told me something else I already knew. The light source must not be flourescent because of the alternating brightness that occurs with them. He then told me something else I didn't know. Some LED lights have some weird wavelength that alternates similiarly to a flourescent bulb. Perhaps my LED's were doing this. I don't know.
But Oehler told me that they were way ahead of me and they had tested many methods at night and found that their indoor lighting system was the cheapest, easiest, and lightest way to chrono at night without going to infared. So he charged me $90 for three new tops, three ballasts and cords, and three 40watt t8 fitting incandescant bulbs. These bulbs are rare and awkward but they burn extremely cool and don't pull much power.
In four days, my nightime rig was here and I went and tested it that night. I have been hauling a generator out to the range all along to light up the gongs for 1k shooting, but this time I used them to run the bulbs on the diffusers. I plugged them in and immediately one bulb blew out. It must have broke during shipping. Well, Oehler told me if that happens, you can still run the chrono on two screens as long as it is the first and the third and you only plug them into the box and leave the middle unplugged. The box will automatically recognize what has happened.
So a quick switch and the remaining two bulbs were in the correct place. Generator on and LED light bars were placed under the target frame to light up the 100 yard targets. An extra flood lamp was placed ahead of the chrono to light up the wind flags. Here is what that all looks like:
First shot through: Perfect read! Next, read. Next, read. I shot 20 shots with the 6br and every one read! Ok, now for the real test. Let's see if my 223 shooting little shiny 40 grain vmax at 4000 fps will show up. It did! All 20 of them and a good group too by the way. [img]/ubbthreads/images/graemlins/wink.gif[/img]
The nightime chrono read every shot and was very reliable. It did however seem to read velocities about 30 fps faster than normal but that was probably because it was only using the two lenses. I have never chrono'd it before with just two so I don't know for sure if that was causing the fast readings.
It also was pretty blinding to shoot through with those bulbs blaring right at me, but a strip of target paper taped in front of the bulb solved that problem easy.
More testing is in order. I will take more pics of the rig and the bulbs next trip out.
Stay tuned for part 2............