Re: Light Refraction for LR
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: XLR</div><div class="ubbcode-body">I had some questions regarding light refraction. Most of my shooting is done at night with generators and spotlights. When my rifle is zero'd at night, I find that it usually shoots approximatly 1 moa lower than in the daytime. I have concluded that it must be due to the sunlight bending the image thus giving me a different zero. Has anyone else ever had this experience?
I have since thought that since air is like a fluid, does higher humidity bend light more than dry climates?
In addition, if you are waiting for a shot and clouds pass over, does your POI change?
Is there a product that measures light intensity that can be plugged into a ballistics calculator to achive better results?</div></div>
I want to preface this by saying, I'm not an expert and don't pretend to be. As late as it is, I figured I'd post a reply, until some of the more seasoned guys here respond.
Um, have you considered some other factors? Some of them that I would think seem a bit more obvious than what you're talking about. What ranges are you seeing this shift of 1 MOA at? Yes, light angle does make some difference in how our eyes are able to use optical system, resolve a target, etc. There's a reason that match shooters have sayings for different light conditions, and how to adjust their hold. So yes, light and how your eyes perceive it can effect where the bullet impacts. There's still some other explanations.
Have you considered the differences in temperature? I'm sure that the temperatures at night that you're shooting in are probably cooler than during the day. How much so, would depend on what time of the day you shoot, and how hot it gets during the day, vs. those conditions at night. Either way, it doesn't take a huge temperature change to result in 1 moa vertical. I would be a bit more worried about that than light conditions if you're not talking about very long of ranges.
Humidity will change your hits, and it's related to changed in air density and how the bullet flies. I would think that has greater effect than how differently it bends the light between you and the target. There are products that measure light intensity, they get used all the time to evaluate different things. I would think evaluation tools for solar cells, and even more accurately, light meters for photography evaluate the intensity of light. Either way, I still think that you're over thinking things and trying to come up with more complex explanation than are necessary. Trying to use those explanations, is making you look for expensive, and complex equipment that probably won't really even give you better results, because the reason you're seeing the POI shift may not be for the reasons you think.
I would document the shift, and if it's consistent, try to figure out differences in your data that are really cause it. This would be the easy way to see if it's related to temperature, light angle, etc. If it's consistent, it's pretty easy to adjust for, and I wouldn't see why you'd need something to measure the light intensity, as long as you can adjust for it reliably. Either way, I think you're making things way overly complex than it is or has to be.
