Newbie Question about Scope Fog (1 Viewer)

Last week, I purchased a Meopta Meostar S2 82 HD with the 30-60 WA eyepiece. This is my first spotting scope, but I read lots of positive reviews so I felt pretty confident spending the money for a quality scope.

I took it out last weekend for the first time and came away very disappointed. I had been playing with the scope indoors, and I decided to take it out to a nearby soybean field to watch some deer. I zipped up the stay-on case, dropped it in my backpack, and made my way to the vantage point (15 minute ride in UTV). Approaching the field edge, I observed a group of deer a couple of hundred meters away. I set the tripod, unzipped the scope, removed the lens and eyepiece covers, and I couldn't see a thing! It was a complete white-out with fog. I figured the fog must be caused from the temperature change from going indoors (21C in A/C) to outdoors (28C+ with high humidity). I then set up in an enclosed blind to watch the field until dark. For the next hour, I watched numerous deer through my Pentax 10X50 binoculars (no fog issue), but the scope never cleared up. I also noticed sweating on the exterior of the scope body which never dried up.

The product specifications say that the scope is "Purged and sealed with inert Nitrogen gas to provide 100% guaranteed fogproof performance." This was definitely not my experience.

Would I have this same problem with other spotting scopes based on the conditions I described? Also, I did not try wiping the objective or eyepiece lenses with a cloth. Do you think that would have helped?

I am just trying to determine if my new scope is defective. Any advice/troubleshooting tips would be appreciated!

Hi Skewerer,

Welcome to the forum.

I would imagine that what your were seeing on your scope was just condensation on the exterior of the scope. The fog-proof guarantee only covers moisture inside the scope.

The temperature difference doesn't seem to be that extreme, but apparently your scope was cold enough for condensation to form. Were your bins stored and transported in the same fashion? Or were they out in the open allowing them to warm up during your ride? The case on the scope helped to insulated it. A scope also has more mass, so it takes longer to warm up. Once the dew had formed the humidity was too high for it to readily evaporate. I have sometimes fanned my scope with my hat to encourage evaporation, although that works best in the Winter when I have accidentally fogged the eyepiece by breathing on it.

The easiest thing to do is to store your scope somewhere a little warmer.

Mike

Thanks for the tips, Mike. The binos were worn via shoulder harness on the way to the field. I cant recall if they were indoors or in my car when I grabbed them (was in a rush). Either one of those factors could have made a difference though by the sound of it.

Do you think wiping the lenses off would have helped? Or is fanning my best option?

Fanning only really helps if they are lightly fogged. Wiping the lenses would have gotten rid of the condensation and if the had warmed up by then they would have stayed dry. I try to touch the lenses of my optics as little as possible in the field, but sometimes it is unavoidable. I have been out during a heavy mist when I had to clear my lens every five minutes. Always make sure to use a clean lens cleaning cloth to avoid scratching your lenses.

Maybe preheating the binoculars would provide a long period of protection.
An incandescent bulb, or a lizard-warming mat from the pet superstore.