Astrolabes and Other Astronomical Devices

The Astrolabe

English: The Astrolabe.
English: The Astrolabe. (Photo credit: Wikipedia)

Although only recently introduced into Western Europe in the 11th century via Iberia, the planispheric astrolabe (Greek: “star taker”) has a long history of use in Andalusia and the Levant, having been built by the Persian mathematician al-Fazari, although probably from ancient Greek descriptions. As an analog calculator comprised of a flattened planisphere and an alilade (sighting ruler), it allows the calculation of a multitude of spherical astronomy problems, assists navigation, helps determine the timing of morning prayers and aids in finding the qibla, the correct direction of Mecca.

The first universal astrolabe, one that could be used by an observer at any latitude, was constructed by Arzachel (al-Zarqali) in Andalusia and became known as the “Saphaea” in Europe. It consists of three main parts: the mater or base, a main plate known as a tympans (or climates) and the intricate rete which marks the position of the fixed stars. Adjusting the device by inserting different plates calibrated for a particular latitude greatly increased its accuracy and applicability.

The construction of an astrolabe without magic using Craft (mechanism) and/or the writing of a tractatus on the use or manufacture of an astrolabe (either Craft (Mechanism) or Artes Liberales (Astronomy)) is a common requirement of the Gauntlet of Andalusian Bonisagus and Jerbiton apprentices. The basic Ease Factor to construct a basic astrolabe is 15 but due to the complex astronomical calculations required, a character can add their Artes Liberales (astronomy) score to their Craft score. The majority of Andalusian devices are calibrated to be used at the latitude of Toledo, as the universal devices are more difficult to construct (+6 to Ease Factor difficulty, require an Artes Liberales (Astronomy) score of at least 3).

As a symbol of knowledge and learning, as well as a practical tool for astronomical calculation, the astrolabe is a common object to be used as a talisman by Hermetic magi of Andalusia or as an invested device enchanted with Enchantment of the Scrying Device (The Mysteries: Revised Edition, page 63). Most devices are approximately dagger sized (x2) and constructed of at a base metal, such as brass or bronze (5 points), requiring 10 pawns of vis to open as a simple invested device, although this limit can be readily exceeded if enchanted as a talisman. Smaller pendant-sized devices (x1) worn on a chain around the neck are not uncommon but more unwieldy skull-sized versions (x3) are also noted. An astrolabe incorporating gold, silver and gems is a common as a status symbol amongst Andalusian magi and raises the vis required accordingly. Although wood astrolabes can function perfectly well, the use of such a cheap instrument would bring derision and perhaps even a negative Reputation as a Pauper to any Andalusian magus who insists on using such an inferior quality mechanism.

The construction of a superior mechanism with Aesthetic Quality of 18 or more (see Art & Academe, pages 123-126 for creating artwork) or the writing of a particularly clear work on it’s construction, equivalent to a specialised tractatus of Source Quality of 10 or more, is viewed very favourably by mature Andalusian magi and may result in a favourable Reputation as an astronomer. As a result of this fascination with astronomical instruments, tractati on these Abilities in Arabic (and less commonly Latin) can commonly be found in covenant and mundane libraries of Iberia and astrolabes of varying intricacy and quality can be bought or traded from specialist traders or private collectors.

An astrolabe provides the following Shape & Material bonuses: +5 measure the stars and heavens, astrology, and navigation. If used at the correct latitude for which it is designed, it provides a +3 bonus for calculating astrological inception, horoscopes and determining the time of day but the user must have an Artes Liberales (astronomy) score of at least 3.

The Quadrant

Hororary quadrant (OASC) sf36-20-54a
Hororary quadrant (OASC)

Developed by the Persian astronomer al-Kwarizmi in the 9th century, basic horary quadrant (quadrant vetus) typically consists of a 6 to 9 inch quarter circle of metal marked with a series of marked graph lines that allows prediction of the time using either equal or unequal hours. By aligning one edge with the sun, the hour of day can be read using a bead and plumb-line and reading off against the markings.

Simple versions using hours of equal length can only be used at specific latitude, limiting their usefulness. Although less commonly used as a talisman, quadrants enchanted as lesser devices with a variety of personal magical effects may frequently be found in the possession of Andalusian magi as they arouse little suspicion amongst mundanes.

A basic quadrant has the following Shape & Material bonuses: +3 measure the exact time of day. It is much easier to construct than an astrolabe, requiring only a Craft: mechanism roll against an Ease Factor of only 9 and little understanding of astronomy. If used at the correct latitude for which it is designed, it provides a +1 bonus for calculating astrological inceptions and requires only a basic understanding of astronomy to use (an Artes Liberales score of 1 or more).

The first complex astrolabe quadrant (quadrant novus) is not constructed till 1288 by Prophatius Judaeus (1236-1304) of Montpellier. It consists of an astrolabe plate folded upon itself twice, containing the same level of information and utility in a more simple to construct device. It provides the same bonuses as listed for a planispheric astrolabe noted above but is cheaper, lighter and somewhat easier to construct (-3 Ease factor difficulty). However, the user must have an Artes Liberales (astronomy) score of at least 5 as the overlapping markings are more difficult to interpret. It is not possible to construct a universal quadrant and each must be set for a particular latitude.

By the fifteenth century, such quadrants will have replaced the astrolabe for most astronomical calculations due to its reliability and simplicity. In your Saga, such advanced astronomical instruments may be invented by Hermetic magi with an interest in applying astrological elements to their magic. See also The Mysteries: Revised Edition, page 52 “The Armillary Sphere” for other related astronomical devices.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: