Cost for a...

How would you handle players wanting to buy these types of devices? Spyglass is 1000gp in Labyrinth Lord.
A compass? How much you think? Does it give a +4 to Navigation rolls? Maybe just a +2 so it doesn’t outright replace that proficiency?

The question being whether the proficiency may be required to use one successfully - an astrolabe is harder to use than a lodestone without being shown how first, or is the equipment required for the proficiency to come into play ?

Michael, spyglasses and compasses fall somewhat outside the assumed technological era of ACKS, so I haven’t priced them out. The spyglass wasn’t invented until the 16th century and the magnetic compass wasn’t used for navigation until the 11th century in China and the 12th-13th century in Europe.
That said, in the 2nd century BC, the Antikythera Mechanism was created, the first mechanical computer, so spyglasses and compasses certainly could have been invented during that time period. I’d suspect 1,000gp is about right.

I’d say a compass could only be used if you had Navigation proficiency and would give a +2 bonus to the roll.

Great stuff! Thanks guys.
What would you price the compass as? Similarly to the spyglass as a higher tech item? Or, lower because it doesn’t require the lenses?

A compass was invented earlier and doesn’t require sophisticated lens-crafting. I’d go with a lower price. 250-500gp.
If you want it to be higher priced, you could justify it by saying that lodestone is rare. You could even make lodestone magical and justify a very high price.

Good thoughts.
I’ll take all this into consideration. Feedback is much appreciated.

When I run ocean adventures, I treat spyglasses as low-grade magic items (worth 1k-10k), and compasses as somewhat less (100’s of gold, and skilled reading). Compasses are in the technological age of most D&D that has ships (ca 12C?), but rare. If lodestone is rare, so might be cordierite, which was theoretically used by Viking sailors to infer the location and declension of the sun in low-light circumstances. It all calls to mind Ryan’s illo of the magic user studying: A ship’s navigator with a small chest of curious stones, metal implements engraved in strange characters- the swords and sorcery equivalent of a binnacle.
I personally like the notion that some of the magic of the world we would recognize as technology- magnets, curved lenses (made by craftpriests, natch), or weapons made from meteoric iron alloys (which was a rare source of steel in non-mining settings).

Very cool, Charlatan.