It has been discussed and debated for a long time that it is safe to expose night vision to daylight with the unit turned off. For the most part that is true. Some have argued that direct sunlight can affect the image intensifiers even without any power circulating through the tube. Unfortunately, several individuals all experienced a sun blem in their night vision goggles a couple days ago.
Night Vision @ TFB:
- Friday Night Lights: Night Vision Blemishes And How To Fix Them
- Friday Night Lights: Understanding Night Vision Specs And Generations
- Friday Night Lights: One Tube, Two Tube, Green Tube, White Tube
Jeffery Melochick of Nocturn Industries recently posted the photo above on Facebook as a public service announcement. He and several other night vision owners experienced a sun blem in their night vision devices. Here is what he posted.
I have a public service announcement for everyone. This is critical so please pay attention. USE DAY CAPS ALWAYS. Previously thought to be common practice, it has been debated recently and we have confirmed officially that YES your image tubes can be severely blemished by direct exposure when pointed at the sun with the power OFF. We have 6 cases from an event this weekend where people ran devices in the stowed position powered off in the day time when the sun was at its highest with no caps on the objectives. Elbit, L3, and Photonis image tubes were all effected and the housing or lens does not matter. This is no longer a theory or myth. It does not happen all the time and the conditions have to be right for it to happen. Do not take the risk, use day caps if you use your device in the day. Pic for reference this came from a customer and it happened to a few of our own devices as well, we confirmed with our devices the power was indeed off. The pattern is very distinct. We will be doing destructive testing in a controlled manner and posting that later.Thank YouEdit: There seems to be confusion. Daylight is fine and not an issue at all. Pointed directly at the sun is the problem.
We know for certain with only 7-8 minutes under direct sun light objective optics are capable of producing 400° to 450° and can leave burns in your image tube. Theoretically speaking, since the blade of grass is not a tube we can’t say this test proves either way. However, much like what @nightvisioninc has said, there are chemicals within an intensifier tube. Heat rays like this can cause those chemicals to separate and cause blems whether your tube is on or off apparently.
Questions we still have:
1. Can your tubes still be damaged when not under direct sunlight, but still outside with no caps? Would it just take longer to cause damage?
2. Does damage only occur between 12:00pm and 2:00pm?
Think we need to test this on a tube what do you guys say?
The simplest solution is to not expose your night vision to direct sunlight. If that cannot be avoided then get lens covers. Completely blacked-out ones like bikini covers are great because they can be stored on the monocular tube housing with bands. Just slide them off when you need to use your night vision. Other people use Butler Creek flip caps. However, drilling a hole in them or using some form of refocusing lens might still allow a sun blem to occur since they do not block out all light but rather refocus that light. Even pinhole day filters may not be enough to protect your tubes.
Jefferey Melochick will be conducting some more experiments to properly document such damages and put this issue to bed but at the same time shed light on it for people to properly care for their devices.