I have a good working chronograph that will not read in direct sunlight. Wasn't a problem in Seattle but since I move to the sun belt I need to make some diffusers for it. Does anyone know what they are made from?

Paul,

The one we use is made of opaque plastic sheet.

The idea is to shield the sensors from direct sunlight, without affecting the light shining on them.

We use the chronograph in our indoor shooting range, and for that we had to install lights directly above the chronograph. We then installed the diffuser above the sensors.

Paul,
Most of the chrono manufacturers sell the diffusers separately as well as the sensors etc. Might check with them, they aren't expensive.
Bill

When I bought my Chrony, many many moons ago, it arrived with no diffusers although the cardboard gates had slots at the top for diffusers.
Maybe the chrony had been used at the gun shop being the first ones to arrive in the country at that time and the diffusers got left behind when the unit was sent to me. Anyway I just cut some out of a thin white plastic lid of an icecream container made of HDPE plastic, strong and flexible and they have lasted for 30 odd years and work extremely well.

I never have a problem in bright sunlight and always get consistent and realistic velocity readings, occasionally checked against subsonic 22RF ammo velocity.

Mind you I do like this early chrony which had the cardboard sighting screens, easily replaced with homemade copies if they get shot up, heavy trigger Webley revolvers good for this!!!!.
The small and precis sighting apertures in these screens seem to give more consistent results than the later models which have the wide V wires with no specific sighting guide.

Original cardboard sighting screen for Chrony:



Chrony set up with homemade sight screens and sunlight diffusers:



Birds eye view of Chrony set up showing sunlight diffusers over skyscreens:

quote:

Originally posted by Saeed:
Paul,

The one we use is made of opaque plastic sheet.

The idea is to shield the sensors from direct sunlight, without affecting the light shining on them.

We use the chronograph in our indoor shooting range, and for that we had to install lights directly above the chronograph. We then installed the diffuser above the sensors.

Saeed,
Do you recall what kind of plastic you used?

Saeed and eagle27,
Is it important to shade the sides of the shooting area or not. The pistol and shotgun ranges face East and West while the rifle ranges face South. I am wondering if I need to build sides that are blacked out or if I can keep them open to the direct sunlight.

eagle27,
Milk cartons are HDPE - will that work or does it have to be completely opaque?

Remembering that the sky-screens actually register the 'shadow outline' of the bullet, arrow or shot that pass over them and like one looking up to the sky it is much easier to see an object if there is a white background and not a bright blue one. Best to use an opaque white plastic that allows diffused light through. Doesn't have to be HDPE but this plastic type is tough and flexible so will last a long time.

Re shielding the screens from the side, I guess perhaps that is why my Chrony has performed so consistently as the cardboard sight screens are folded so do have blackened sides which will protect the skys-creens from oblique sunlight. This shows in the photos I posted.

Oehler Model 35

Paul,

If you look at the link above you will see the Oehler that we use.

I put 6 small pieces of Velcro on each of the two sides of the orangle tops that fit over each sky screen.

I then cut a piece of opaque plastic to fit over all the 3 sky screens and put corresponding Velcro on that to keep it on the sky screens.

The plastic we used looks like the wax paper used in the, kitchen by the ladies to make cookies.

In fact, I am sure that wax paper would work too. The only reason we used the plastic was for removal and use again.

My thanks to both of you, Saeed and eagle27.

I tend to over think and then over engineer and that way it never fails. I have some plastic that I will try and I will also use side shades to keep out any random light.

I may have to rebuild my beam to do this as there are no provisions on my beam to place diffusers or shades. All that's left is to draw it out and build it.

Paul, if it is big enough to suit your needs, I use plastic milk cartons that are cut to size for screens. If you need it thicker, just glue two strips together.

I have no pictures but I run mine inside a 4 sided cardboard box. It is simple and cheap

Just put it in a box.... IE a tunnel made from cardboard

I built a cardboard box to fit my beam 3.5" and it widens at the top to 8". I cut the openings in the ends that taper from one inch at the bottom to four inches up seven inches. The overall height of the box is 12 inches and the openings are just about centered. The top of the box has two openings that are 2 inches wide that are centered over the sky screens. I have "windows" made from milk cartons and will try it out when the temps get warm enough to shoot.

Thanks for all the help folks!

Depending on sun angle I find that sometimes I have to add shades to the sides and/or the fronts and backs of the sensors. I have an old Pact; you can get diffusers from them. The plastic in 1 gal. milk jugs might be a cheap fix?
C.G.B.

quote:

Originally posted by cgbach:
Depending on sun angle I find that sometimes I have to add shades to the sides and/or the fronts and backs of the sensors. I have an old Pact; you can get diffusers from them. The plastic in 1 gal. milk jugs might be a cheap fix?
C.G.B.

cgbach,
Any diffusers I bought would need to be modified to fit my set-up because back when I bought my Pact they didn't come with a beam - I had to make it myself. I found places that I could buy diffusers but I would have had to do the same thing I already did - make a box to shade the sky screens and mount the diffusers to. Since I have one made now the worst case is that I would have to buy diffusers and cut to fit. I believe that this setup will fix the problems.

Besides free is always a good price as long as it works.

PaulS,
Most of the times we use a ProChrono Digital to chronograph shotgun slug loads. The chronograph is put about 20" lower than the muzzle line and NO diffusers. We didn't had any false velocity readings, even with direct sunlight. And the sun really shines here (Greece).

Lefteris

quote:

Originally posted by Lefteris Vassiliadis:
PaulS,
Most of the times we use a ProChrono Digital to chronograph shotgun slug loads. The chronograph is put about 20" lower than the muzzle line and NO diffusers. We didn't had any false velocity readings, even with direct sunlight. And the sun really shines here (Greece).

Lefteris

The shotgun slug is a large object with a dull finish and it's own built in diffuser (usually a white opaque wad) so is possibly the best object to create a shadow for the chronograph photo cells to pick up. I also found that I got very good consistency when chronographing shotgun rounds even just with shot charges.