An observation device includes a housing and an optical lens having a field of view. The housing includes an outer dome having at least one transparent portion and an inner dome. The optical lens is accommodated within the housing. The outer dome is transparent in the field of view of the lens and is configured to protect the lens. The observation device is resistant to impact by an object with a maximum impact energy of a first magnitude. A like observation device, but lacking an inner dome, is resistant to impact by the object with a maximum impact energy of a second magnitude. The ratio between the first magnitude and the second magnitude is at least 1.1.