Celestial Navigation · Hour Angle — Meridian Angle t
The meridian angle (t) used in some sight-reduction methods is measured from the observer's meridian:
- AFrom the celestial equator
- BAlways westward 0° to 360°
- CFrom Greenwich only
- DEast or west, 0° to 180°, to the body✓ Correct
Explanation
Local hour angle is measured westward 0°–360°. The meridian angle t is the same geometry expressed 0°–180° labeled east or west, whichever is smaller, convenient for the navigational triangle. When LHA is less than 180° it equals t(W); more than 180°, t(E) = 360° − LHA.
Authority: Bowditch (Pub. No. 9), Hour Angle
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