The "Deep Sky" pictures aren't a problem. You'd need zillions of more megapixels to compute axis offsets and get rough geolocation results out of angular differencies when you shoot pictures of bright objects many lightyears apart.
What's more sensitive in terms od OpSec are wide angle pictures of the milky way or zodiac signs, including a horizon with some possible details.
One could calculate roughly when he knows the exact time of day and timezone, because elevation and direction, also angle of objects relative to the ground and horizon are given over the course of a year, even more so if solar planets are included in the pics. Basic astronomy knowledge wouldn't be enough, but if someone knows someone, you know, you can never know...

Next one?  


Yes, that was what i though when i bought my first telescope eight years ago, just to sell it again a few months later. You have to put in some good effort to get results that keep you going at it