In another thread
http://www.birdforum.net/showthread...0085#post830085
the question arose about the temperature ranges optics are made for. As this important topic seems hidden in that thread, I am starting a new thread here. I am truly concerned about the information that Zeiss only tests their gear to +40C, if the information in that other thread is correct. Even the quoted +55C for Leica seem low, considering the fact that many optics stay out in the sun for hours. And the exposure must be worse for scopes than it is for binoculars.
No one here seems to leave their optics in a closed car (windows up, not running, and no people in it) in full sun for any length of time. In Panama, guides kept the drinks in a cooler with a gelpak or ice (didn't notice which). We started using a cooler, because they're cheap, effective, convenient, and keep the optics out of sight. There isn't always a spot in the shade.
That being said, for birding in warmer climates, if it's OK for humans, is it safe to assume it's OK for optics?
Mike