Wow it's tough to choose between each idea, they're both pretty good..
I think ultimately I would have to lean towards the 'rangefinder' spotting tool idea though, as it encourages teamwork slightly more than the map idea - if only because it actually requires another member of the crew to be standing with their spyglass out and relaying the information to the others, whereas the map is available to everyone no matter what they're doing, so people would likely just check it for themselves.
Although since the map would provide a scale rather than the exact distance of the target, it would take more time to work out than the spyglass, so the spyglass would be more convenient and easier to use in battle (assuming the crew member using it didn't already have their hands full with their normal duties).
If that seems like it might be making things a bit
too easy though, you could always outfit the spyglass for
stadiametric rangefinding rather than just giving an exact readout of the distance, forcing the user to work out the distance for themselves.
The only problem with this is that it's generally used to find the distance of something whose dimensions are known (e.g. for a sniper to gauge the distance of a human target), but the various ships are wildly different in size.. Still, it might add an extra level of challenge, for people who like to do everything on hard mode.
Alternatively the rangefinding scale could adjust itself according to the ship that's been spotted. This would require the person checking the range to focus on the ship for several seconds to make the adjustment before they could use it to check the range.
Or if we want to keep things a bit more plausible (rather than including magically self-adjusting lenses), the spyglass could come complete with a set of lenses, one for each ship type, which the player would then flip through to find the one with appropriate scale. If this were to be included, the rangefinding spyglass could be included as its own distinct item separate from the regular spyglass, which would have the different set of marked lenses, but would be unable to zoom in.
The 'spotting' ability could also be different - instead of permanently marking the target, it could temporarily add the target distance onto the enemy ship (visible to the entire crew), which would fade away after a few seconds. This would only happen if the player clicked when the enemy ship was located in the correct position on the rangefinding scale, and would only be a very general number (in 10 meter intervals for example) rather than a specific distance. It would need to have some kind of cooldown to avoid people spamming the ability constantly.
