Question -zeroing a thermal scope in the daytime?

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dave3006

Active member
I have an AGM Clarion 640. I want to zero it for a different load. I usually go right at dawn before the sun comes up. I use a box at 50 yards with a 1" hole and I put a hand warmer inside to heat it up.

I can't get to the range in the morning for a while. Do you think it will be a problem do check zero during the day? I was going to go at noon. The temperature will be 52 degrees.

Can I get a good zero in these conditions? Or, am I wasting my time?
 
I tilt the target about 20 degrees and use a 1" square of alum foil for 100yds and a 4"sq. for 200yds. Check different color pallets as I find that black works best in some daylight conditions and white in others (depends on cloud cover/time of day -location of sun, I DO NOT want the sun directly shining on the foil. Also be sure to focus at each range and NUC before each shot.
 
I've zero'd mine in the middle of the day in Texas summer with the hand warmers.
Screenshot 2025-03-11 180138.jpg
 
I sight in during mid day. I use one of those disposable chemical hand warmers. Activate the handwarmer, attach it to a backstop. Then staple a sheet of paper with a 1” or so diameter hole in the center over the hand warmer. Have the hole in the paper over the hand warmer. Works quite well for me.
 
The foil can be a great option depending on sun location in relation to the target.

I disagree with using handwarmers. Heat signature from handwarmers and lit cigarettes expands dramatically beyond their physical edges. I much prefer an ice cube or a frozen cherry tomatoe in a plastic bag stapled to the target.
 
I have used hand warmers in the past. But, I don't staple them to anything. I cut 1" squares in a box, toss a hand warmer in it, a few rocks to hold the box in place, and seal it up. There is no bleed through this way.
 
I use a couple of ice cubes in aluminum foil, set on white hot it shows as black in the scope, very easy to see. you could use a second one to mark where you are hitting. I just tape it to the target. I take a big tumbler with a coke in it to the range and just fish a couple of cubes out and carry some pre made pouches.
 
Another thing I've done is pretty simple. White printer paper with black electrical tape in a cross pattern. The temperature differential in the daytime usually gives a good sight picture. I put a half of a hand warmer on the center, but really it's the cross of the tape that I settle the crosshairs on. I also agree that color palette changes can make a world of difference. Black on bright day seems to work for me, whereas I use white hot at night.
 
The most ingenious way I have seen, and it isn’t an option for everyone was this.

This fellow would take an 8” round steel gong target and heat it up with a propane torch. He would then use his circle dot reticle and zoom his optic until the circle was the same size as the perimeter of the gong which would put the dot dead center of the gong.

I haven’t tried it, but I can certainly understand the logic behind it. I use aluminum tape and tilt target back myself. Works fine for me. I have heard black tape on the foam sheets you get at craft stores works well also. Haven’t tried it personally.
 
My issue with hand warmers, heat rises. So the signature center is slightly above the center of the hand warmer. When I use them I glue a 2" section of pool noodle on to the target holder(usually cardboard) than mount the target with a 1" hole in it over the noodle center(hand warmer stuff inside the noodle). This will give me a very defined round aiming point without the blurred looked. I like to sight in on the north side of a tree line in the morning, in shade and slightly cooler temps than out in the open.
 
Just sighted mine in this morning using a foot warmer - not a problem. Check/verify final zero with day scope on the other rifle to see the holes. Sorry didn't keep the target.
 
popper43 said:
Yes handwarmers appear large but I 'center' it on the reticle and verify the hole.
Click to expand...
Yes, but hand warmers are pretty warm and heat rises. The heat signature will be taller than it actually is. If you center that then you will likely be a little higher than the center of the hand warmer. I usually aim at the bottom of the heat signature.
 
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