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Question see title; further explanation: what I mean is especially in relation to identifying time (of month, year) and location/heading based on the location of celestial objects and, say, a standard of difficulty classes for respective tasks (like, identify time of year, identify heading, with clear sky, with partially clouded sky, at day, at night, etc.)

If yes, which standard D&D rule book or supplement contains this ruling?

[Annotation: By "canonical" I mean that it's approved and published by Wizards.]

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3 Answers 3

Some of what you're asking for is covered by

Knowledge (geography)

"While Profession (sailor) covers the maneuvering and handling of a ship," says Stormwrack on page 86, "the science of navigation requires a distinctly different set of training--mathematics, geometry, optics, and astronomy, among other fields"--emphasis mine. Detailed rules are then given for plotting courses, which--unless you need to determine that the stars are right for summoning an elder evil or that tomorrow night your follower will become a wereshrimp--should be pretty much all one does with D&D stargzing.

However, extrapolating from the given rules means that a character could approximate that something was wrong with the stars he's seeing. If the character knows it usually takes 1 day to sail from Funkytown to Erotic City, yet based on his plot course check using his Knowledge (geography) skill he determines it takes 3 years, the character can totally figure the stars may have changed. Some backward math should even let him figure out by how much.

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Survival covers navigating and determining heading. In most cases, celestial navigating would be used for such tasks (though Survival does not actually assume or require that this be your method).

Knowledge of the movements of the heavens would probably be covered by Knowledge (geography) or Knowledge (the planes), depending on the cosmology of your setting. Note that Knowledge (geography) gives a synergy bonus to Survival checks made to avoid getting lost.

Profession (astrologer) is required by at least one prestige class (Sublime Chord from Complete Arcane), though no specific details for using it do any of the things you’re asking about exists.

The creation of new skills in supplements is generally avoided, and at least in my opinion, is a mistake where it happens. The new skills cannot (easily) be distributed appropriately as class skills, and furthermore 3.5 already has far too many skills. I feel strongly that including these kinds of skills as part of existing skills is more appropriate than creating a new skill. This includes a new Knowledge subskill: Knowledge (astronomy) is too specific, and introduces the headache of determining which classes do and do not receive it as a class skill.

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So there is no such canonical skill (survival including the heading determination thing, but nothing actually sepcifically astronomy-based)? –  DeadCommunist Jul 3 '13 at 6:16
@DeadCommunist As far as I know, no. It's too specific for a Knowledge skill all to itself, and the, heh, practical applications of it belong to Survival. –  KRyan Jul 3 '13 at 13:22
Astrologer is detailed in a dragon magazine article (Issue 340) which gives additional benefits from a "horoscope" that gives a random +1 and -1 to various rolls. I didn't this as add an answer since Astrology is "magic" and Astronomy is "science" and the question is about the science of the stars. –  James J. Regan IV Jul 3 '13 at 17:04
@JamesJ.ReganIV Eh, in a world where magic is real, the line blurs considerably, which is why I mentioned the prereq. But yeah, sounds like they're not using it for keeping track of the stars so much as using it as a form of divination. –  KRyan Jul 3 '13 at 17:14
@KRyan One could argue that divining through astrology requires keeping track of the stars. Real life astrologers, historically, were also astronomers by necessity. –  called2voyage Jul 3 '13 at 21:09

Navigating your way successfully is covered by the Survival skill:

DC 15: Keep from getting lost [...]

You could easily argue (as a player) or rule (as GM) that Knowledge (Astronomy) could give you a +2 Synergy bonus on checks to avoid getting lost, just like Knowledge (Geography) does.

From a simulation point of view this makes sense – it doesn't matter how much you know about celestial mechanics if you have no practical experience using it to navigate across land or sea. Astronomy can help you, but the real test is your ability to move around in the wilderness using landmarks (which stars are), not whether you know that star cluster is The Dragon's Eye or The Serpent's Tail.

For figuring out calendar time and high-level location (such as hemisphere or approximate latitude) there is no existing skill that covers that. It seems reasonable to me that Knowledge (Astronomy) would be able to give you that information, yes. Since the Knowledge skill is supposed to be specified with a specific domain of knowledge, using it to represent astronomical knowledge is well within the rules. (The Knowledge specialisations listed in the SRD are not an exhaustive list; they are listed because they are mentioned elsewhere in the rules as having certain mechanical impacts, not because they are the complete list of legal Knowledge specialisations.) Go for it!

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