Astrography

Astrography is the science of mapping interstellar space.

• Sometimes Astrography is mistaken for the related science of Astrogation.

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Overview:

Astrography

Astrography is the art and science of mapping out interstellar space. An astrographer is someone who maps out interstellar space.

Astrogation

Astrogation is the actual planning of the navigation of spacecraft. Or the planning of a route through space, either in interplanetary or interstellar travel. An astrogator is someone who navigates a spacecraft, or starship, through interstellar space.

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Please see the following AAB articles for related information:

• Astrography
  • Applied Astrography
    • Imperial Grand Survey
  • Physical Astrography
    • Cluster
    • Main
    • Rift
    • Star
    • Trace
  • Social Astrography
    • Charted Space
    • Wildspace
• Cosmology
  • Black Hole
  • Jumpspace
  • Light Speed
  • Nebula
  • N-space
  • Universe

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Description (Specifications)

Basic to any science of mapping is a coordinate system. The scientific system used by the Imperium is based on rings of longitude, rays of latitude, and parsecs. By convention, rays of latitude and rings of longitude are measured from a starting point at Reference (Core 0140), the world where the data from the First and Second Imperial Grand Surveys are stored.

The concentric ring passing through Reference/Capital is labeled the 10,000th ring, and is used as a baseline. Similarly, the ray of latitude extending from the center of the Galaxy through Reference/Capital is designated as the first ray. Measurement is in parsecs, counting in the trailing direction. Computation reveals that the circumference of the 10,000th ring (r=10,000) is 62,832 parsecs. Counting spinward uses a subtraction from 62,833, which is the equivalent of the zero baseline.

For example, Regina, of the Regina Subsector, in the Spinward Marches, is 9930 ring/ray 62723.

• The format for expression of location is xxxx ring/ray yyyyy, where xxxx is the ring of longitude (distance from the galactic core in parsecs), and yyyyy is the distance of the ray of latitude (in parsecs) from the first ray of latitude, measured along the ring of longitude in the trailing direction.

Four Prime Directions

The four prime Astrographic directions are:

• Spinward (In the direction of the orbital spin of the galaxy)
• Coreward (Towards the center of the Known Galaxy)
• Rimward (Away from the center of the Known Galaxy)
• Trailing (The opposite direction of orbital spin of the galaxy)

Please see Galactic Directions for more information.

Units of Measure

Please see to learn more about general astrographic organization:

• Charted Space, or Known Space (all charted sectors)
• Domain (4 sectors)
• Quadrant (1/4 of a sector or 4 subsectors)
• Sector (1 sector) (Called a province by the Zhodani)
• Subsector (1/16 sector) (Also called districts)
• County (Less than 1/16 of a sector) (Usually a multi-world planet grouping)
• World (Less than 1/16 of a sector) (A single planet)

Astrographic Measurement Data Table

Term	Sector Equivalent	SubSector Equivalent	Notes
Charted Space	All known sectors	All known subsectors	All of charted space is still but a fraction of the known galaxy. Sometimes informally referred to as "known space".
Domain	4	64	Domains often include attached nearby territories in their realm of control. Many domains don't include complete (100%) control of the entire domain. Occasionally known as "demesnes".
Sector	1	16	Also known as "marches", "matrixes", "provinces", "reaches", and "regions" among other titles.
Quadrant	1/4	4	Sometimes confusingly used to refer to a whole Sector rather than several (four) subsectors. In some antiquated pre-Imperial measurement systems, four sectors formed a super-sector composed of four sectors each called quadrants.
Subsector	1/16	1	Sometimes referred to as "Districts". A County is a political measurement that may be smaller or larger than a subsector.
World	Fraction	Fraction	A single world, overseen in the Third Imperium by an Imperial noble of the rank Marquis or above. Groupings of nearby worlds are called clusters.

Please see the following articles for related information:

• Counties
• Districts

History & Background (Dossier)

Imperial Science: This mapping system is highly Imperio-centric, and other systems are used by other peoples and races outside the Imperium. This system has gained wide acceptance, however, among Imperium dominated client-states, human and otherwise. This mapping system breaks down and is prone to error beyond certain limits. It does serve admirably for a band approximately 400 parsecs wide at a longitude of 10,000 parsecs, which is a region precisely centered on the Imperium.

In ordinary discourse, a world is referred to by its name then sector and parsec/hex in parentheses.

For example, the homeworld of Archduke Norris is Regina (Spinward Marches 1910): That is, the world Regina is in hex 1910 in Spinward Marches Sector.

• When specifying the location of sectors, a coordinate system is used with Core sector being at (0, 0).
• Thus the Spinward Marches would be at (-4, 1) and the Reavers' Deep would be at (-2, -2).
• This can be better viewed on the Charted Space map.

Named Astrographic Features & Locations

Please see to learn more about named astrographic locations:

• Abyss Rift
• Behind the Claw
• Bradley Barrier
• Calibration Point (Deep space refueling points)
• Delphi rift
• Dudin-Bolivar Rift
• Dunmag Sargasso
• Empress Wave
• Great Rift
• Helix Rift
• Horlein asteroids
• Lesser Rift
• J-4 Gn'hk'r Jump Bridge
• J-5 Trans-rift Hierate Route or Verge Connector
• JumpStart
• Main
• The Maw
• Misplaced Stars
• Outrim Void
• Pact-Remnants Mainbridge
• Pelican Nebula
• Rimward Gap
• Saris-Yenisei Bridge
• Sirius Gap
• Trojan Bight or Outrim Void
• Wilds
• Windhorn rift

Astrographic Distances Data Table

#	Base Unit	Astronomical unit (AU)	Light-scale (Imperial Standard)	Parsec (pc)	Kilometers (km)	Miles (mi)
1.	Parsec (pc)	206,260 AU	3.2637 ly 170.069 lw 1190.484 ld 28,571.616 lh 1.714×106 lm 102.858×106 ls	1.0 pc	30.856 trillion km	19.173 trillion miles
2.	Light-year (ly)	63,200 AU	1.0000000 ly 52.143 lw 365.00 ld 8760.00 lh 525,600.00 lm 31.536×106 ls	0.3064 pc	9.454 trillion km	5.875 trillion miles
3.	Light-week (lw)	1,212.055 AU	0.0192 ly 1.0 lw 7.0 ld 168.0 lh 10,800 lm 604,800 ls	5.876×10-3 pc	181,314 million km	112,630 million miles
4.	Light-day (ld)	173.151 AU	2.738×10-3 ly 0.143 lw 1.0 ld 24.0 lh 1440 lm 86,400 ls	8.395×10-4 pc	25.902 billion km	16.094 billion miles
5.	Light-hour (lh)	7.215 AU	1.1408×10-4 ly 5.9524×10-3 lw 0.0417 ld 1.0 lh 60.0 lm 3600.0 ls	3.498×10-5 pc	1.079 billion km	670.6 million miles
6.	Astronomical unit (AU)	1.0000 AU	1.581×10-5 ly 0.0008 lw 0.0058 ld 0.1387 lh 8.3195 lm 499.1681 ls	4.848×10-6 pc	150 million km	93 million miles
7.	Light-minute (lm)	0.1202 AU	1.901×10-6 ly 9.941×10-5 lw 6.944×10-4 ld 0.017 lh 1.0 lm 60.0 ls	5.830×10-7 pc	17.99×106 km	11.18×106 miles
8.	Light-second (ls)	0.0020 AU	3.1688×10-8 ly 1.6534×10-6 lw 1.1574×10-5 ld 0.0003 lh 0.0167 lm 1.0 ls	9.7159×10-9 pc	299,792.458 km	186,282.397 miles
9.	Mile (mi)	Fraction	Fraction	Fraction	1.609344 km	1.000000 mile
10.	Kilometer (km)	Fraction	Fraction	Fraction	1.000000 km	0.621371 mile

NOTES:

• A Standard Day is exactly 24.00 hrs long, by definition.
• A Standard Imperial Year is exactly 365 standard days long, by definition.

• A Terran Local (Solar) Day is exactly 24.00 hrs long, by definition (1.0000 standard days)..
• A Terran Rotational Period is 23h 56m 4s long (0.9973 standard days).
• A Terran Orbital Period (Year) is is 365.2564 standard days in length (1.0007 standard Imperial years).

• A Vlandian Local Day ("Drandir") is about 31.8 hours long.
• A Vlandian Rotational Period is 31h 48m 18s long (1.3252 standard days).
• A Vlandian Orbital Period (Year) ("Gurkula") is 478.72 standard days in length (1.3116 standard Imperial years), or 360 drandir.

• A Sylean Rotational Period is 24h 4m 1s long (1.0669 standard days).
• A Sylean Orbital Period (Year) is 364.97 standard days in length (0.9999 standard Imperial years).

References & Contributors (Sources)

This list of sources was used by the Traveller Wiki Editorial Team and individual contributors to compose this article. Copyrighted material is used under license from Far Future Enterprises or by permission of the author. The page history lists all of the contributions.

• Classic Traveller Supplement 8 Library Data (A-M)
• Classic Traveller The Traveller Book
• GURPS Traveller: First In
• Author & Contributor: Lord (Marquis) and Master of Sophontology Maksim-Smelchak of the Ministry of Science