Pretty good thread!
"Watch glasses" weren't issued to ships, they were one of the things checked before going in for the dreaded LT exam in the Royal Navy anyway. From what I understand, those were brutal oral exams in front of "salty" old sea Captains and Admirals and sometimes lasted upwards of 8 hours!!!! In the military today we call them "seabag" inspections. Basically your officer or chief inspected your uniforms and items onboard to ensure that you had all the necesary items before sailing or going ashore to be transferred to another unit.
One of the improved things we use today is the Night Vision Goggles or NVG's. A cool feature of these is that light, any light, is visible at ranges far exceeding the radar well over the horizon. I once spotted a "loom of light" (this is how we reported it on look out) at around 34 miles from the target. The radar could not see it. Needless to say we did our best interception work on the drug runners at night.
Lastly, the higher you get on a ship, the farther you can see. We used to have a calculation for that, but I have long since forgotten it. Something like one more mile of distance every 14 feet up you got or something weird like that. Although, with billowing white sails, it must have been a real pain in the bilge to see some of those ships on a cloud background!
-Todd