Navigation on other Planets
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In which we list some of the Navigational numbers for Alusia, along with comparisons with two other worlds explored by the author.
Types of World
There are many types of plane or planet (a planet is one of several complete worlds within a plane). Some worlds are flat and circular, with defined edges, or which extend infinitely in all directions. Others are spherical. Toroidal and hollow spherical worlds have been reported. Some planes have no bodies of water at all, such as some of the elemental planes, or the Void. Many very small worlds are an artificial or abstract shape, while others have no objective form or structure at all. Alusia is a spherical world, as are most of the more conventional worlds visited, or at least sailed upon. For the Navigator, it is important to realise that only the Spherical worlds obey more than the smallest portion of the rules and regularities spelt out within this guide. Longitude and Latitude, Declination and Bearings, the Circles (Equinoctial, Arctic, Zodiac, etc), and other key concepts simply do not apply to these other worlds. If a Navigator must ply these foreign waters, a Pilot is heartily recommended.
Types of Spherical World
In that all spherical worlds are similar, the underlying principles of navigation do not change; but in that the details of each world or planet differ, so must the values applied to the principles of navigation. From the travelling of various Navigators, it seems that Alusia is one of a number of worlds with very similar properties, and the same values can be applied within each of these worlds, except when actual differences are noted. A second type of world, of which Earth is a typical member, is broadly similar to Alusia, but with a number of small changes leading to much more unstable patterns; these worlds are almost invariably much lower in magic than Alusia. A third world type, included as way of illustration, is the world of Thunor, a planet in the planes of both Alusia and Earth, and also some of their analogues; Thunor has 2 very small, fast moving moons which are hard to track.
Properties of Spherical Worlds
It is very necessary that upon first setting foot on a foreign world a Navigator determine some basic facts, before they rely on their existing knowledge which may steer them into tragic error. The local season, length of the year, day since the start of the season, current cycle of the Moon and Latitude is usually sufficient, for other matters can be observed and fixed from these. However, for calculations of greater precision such as the reliable predicting of eclipses, more information is required such as the position of the Dragon's head and tail, the Epact or place in the Saros cycle, and so forth. A local Almanac or Astrologer can usually provide this information. And to use the provided system of automated tables and charts, you will need to update the list marked "SeasonalConstants.js" with values as listed in the Table of Properties, remembering that the calculated values need not be replaced. And this will serve you well for the first 364 days after the first day of Summer, but the Western Kingdom calendar prevents the display of the 365th day and so on, this being of little annoyance on Earth, but a great deal on Thunor where the last 306 days of each year are not covered, and where the length of the day is not 24 hours, but nearly 40 minutes longer, and my automated tables do truly founder. Upon this occurrence, still an able student may work out any required numbers from first principles, or by adapting and modifying the tables and charts in the associated files, or if I have sufficient leisure and receive direct request, the relevant tables may be further modified for such purposes.
Table of Properties
| Alusia | Earth | Thunor | Comments | |
|---|---|---|---|---|
| Nautical mile | 6080 | 6079 | 3240 | Feet in a nautical mile |
| Solar Constants | ||||
| Day Length | 24 hrs | 24 hrs | 24:40 | Hours in a Day |
| Year Length | 364 | 365 ¼ | 670 | (Local) Days in a Year |
| Solar Tilt | 23°30' | 23°28' | 25° | Degrees from the Elliptic of the Sun's path |
| Solar Eccentricity | 6/360 | 6/359 | 6/60 | Ellipse of Orbit round sun |
| Solar Ellipse Offset | 60 | 63 | unknown | Day of year closest to sun |
| Solar Tilt Offset | 45 | 203 | unknown | Day of year of Summer Solstice |
| Solar Calculations | ||||
| Solar Arc Day | 0.99 | 0.98 | 0.54 | Average # degrees the Sun moves through the Zodiac in a day |
| Solar Arc Minute | 3.99 | 3.99 | 4.10 | Average # minutes for the Sun to move one degree through the sky |
| Lunar Constants | (Phobos) | |||
| Full Moons Per Year | 13 | 239/19 | 3 / day | Average # Full Moons Per Year |
| Lunar Tilt | 5°06' | 5°06' | 1° | Degrees the Moon varies from the Sun's path |
| Lunar Eccentricity | 20/360 | 20/361 | 20/2000 | Ellipse of Moon round Planet |
| Lunar Ellipse Offset | 152 | variable | N/A | Day Moon starts ellipse in Saros Cycle Year 1 |
| Lunar Tilt Offset | 7 | variable | N/A | Day lunar tilt crosses planet's plane in Saros Cycle Year 1 |
| Draconic Progression | 3 | 0.9 | N/A | Tilt regression per Saros Cycle |
| Anomalistic Progression | -7 | -2.1 | N/A | Perigee progression per Saros Cycle |
| Sidereal Frequency | 252 | 241 | N/A | # of Sidereal Months in a Saros Cycle |
| Draconic Frequency | 255 | 242 | N/A | # of Draconic Months in a Saros Cycle |
| Anomalistic Frequency | 245 | 239 | N/A | # of Anomalistic Months in a Saros Cycle |
| Lunar Calculations | ||||
| Synodic Month | 28 | 29.53 | â…“ | Days between Full Moons |
| Sidereal Month | 26 | 27.32 | N/A | Days taken for the Moon to move through the Zodiac |
| Saros Year | 6552 | 6584.4 | N/A | Days for Moon path to repeat |
| Saros Cycle | 18 | 18.027 | N/A | Years for Moon path to repeat |
| Draconic Month | 25.694 | 27.208 | N/A | Days for Moon to cross the Elliptic twice |
| Anomalistic Month | 26.743 | 27.55 | N/A | Days for Moon to complete one elliptical orbit |
| Synodic Arc Day | 12.857 | 12.191 | 1080 | Average # degrees the Moon 'slips' each day |
| Sidereal Arc Day | 13.846 | 13.177 | N/A | Average # degrees the Moon moves through the Zodiac in a day |
| Anomalistic Arc Day | 13.462 | 13.067 | N/A | Average # degrees the Moon completes of its Orbit each day |
| Draconic Tilt Arc Day | 0.165 | 0.049 | N/A | Average # degrees the Lunar tilt regresses each day |
| Lunar Orbit | 24:53 | 24:50 | 8:13 | Average # hours for Moon to apparently orbit the Planet |
| Lunar Arc Minute | 4:09 | 4:08 | 1:22 | Average # minutes for the Moon to move one degree through the sky |
| Eclipse Constants | ||||
| Sun Diameter | 30' | 32' | 20' | Average diameter (degrees) of Sun viewed from Planet |
| Moon Diameter | 30' | 31' | 04' | Average diameter (degrees) of Moon viewed from Planet |
| Planet Diameter | 1°54' | 1°53' | 20° | Average diameter (degrees) of Planet viewed from Moon |
