Astrolabe

 Source Adventurer’s Armory

This device consists of a flat disc upon which two other discs are mounted. The mounted discs can rotate on a central axis, allowing them to spin and move as days pass. The bottom disc represents the latitude of the user; an astrolabe is useless if the user is outside the preset latitude. The upper disc represents the sky, and is filled with astronomical features. Anyone can be shown how to use an astrolabe at night to determine the date and time (which takes 1 minute).

Benefit: When using an astrolabe, you can make a Survival check using your Intelligence modifier instead of your Wisdom modifier to avoid becoming lost. An astrolabe grants a +2 circumstance on Knowledge (geography) and Survival checks to navigate in the wilderness (and on Profession [sailor] checks to navigate at sea).

The following additional/alternate information is from Pirates of the Inner Sea:

This device consists of a flat disc upon which two other discs are mounted. The mounted discs can rotate on a central axis, allowing them to spin and move as days pass. The bottom disc represents the latitude of the user; the upper disc represents the sky, and is filled with astronomical features. Anyone can be shown how to use an astrolabe at night to determine the date and time (which takes 1 minute).

Benefit: An astrolabe grants a +2 circumstance bonus on Knowledge (geography) and Survival checks to navigate in the wilderness (and on Profession [sailor] checks to navigate at sea).

Occult Lore
Author Keith Baker, Adam Bank, Chris Jones, Scott Reeves, and Elton Robb
Series Lore
Publisher Atlas
Publish date 2002

Item Market	Cost
Astrolabe	100 gp
Authority on Formulae	50 gp

ASTROLABE

No astronomer’s kit is complete without this mechanical tabulator vital for solving stellar calculations. ‘Planispheric’ astrolabes (so-called because they provide a flat, or plane, view of the heavenly spheres) enable stargazers to calculate the position of the sun and other major nearby stars with respect to both the horizon and the meridian (the imaginary north-south line connecting the geographical poles). The typical planispheric astrolabe measures 3 to 18 inches and is made of brass or iron. It consists of several principal parts: the mater, a base plate with a network of lines representing celestial coordinates; the rete, an open-pattern disk (with a ‘map’ of the stars, including orbital circles, that rotated on the mater around a center pin corresponding to the north celestial pole; and the alidade, a straight rule used for sighting objects in the sky. Most astrolabes also have one or more climates, which are rotating plates engraved with coordinate lines for different latitudes placed between the mater and the rete. An astrolabe of this type costs 100 gp.

Masterwork astrolabes are wonders of engraving and engineering. A masterwork, planispheric astrolabe costs 150 gp and provides a +2 circumstance bonus to computing astrological spell formulae.

AUTHORITIES ON FORMULAE

These are dense texts describing the various techniques for computing horoscopes, written by famous ancient astrologers. They cost 50 gp each.

masterwork authorities are artfully illuminated, carefully glossed, and accompanied by companion, explanatory scrolls. masterwork authorities cost 100 gp each and grant a +2 circumstance bonus to one type of horoscope, depending upon the authority.