1 - NGA

MIL-HDBK-850
vertical angle, if meaeurest to the right timb in
lhe a.m., then the angle should be measured to
Ihe feti limb in the p.m. The same limb shoutd
be observed In vertical angle. The mean of the
two horizontal angles, with smell correction for
the change in the Sun’s declination during the
Interval from the a.m. 10 Ihe p.m. readings,
@res a reeutling horizontal angle 10 the
meridian.
equal-eltltude obaervatlona—
Observatbns of celestial objects al a fixed
altitude (such as by an aatrolabe) taken at more
or teas uniformly spaced azimuths around the
horizon
equal-araa map projactlon—A map
prmjectbn havin~ a mnstant area scale. Such a
projection is not mntorrnal and is not used for
navlgarlon. Also called aUthallC map
projection; equivalent map projection.
eqIJ8t10n of tha equinox—The difference
behveen the mean and true right ascensions of
a body on the Equator, thus the difference
between mean and apparent sidereal time. Also
called ntnatlon In tight aacenslon.
equallon of tlma-The algebraic dillerence
in hour angle between apparent solar time and
mean solar time, usually labeled “+. or .-. as h is
to be applied to mean solar time to obtain
apparent solar time.
equation—Seis angle equation; azimuth
equetlon; condition ●quation; correlate
equallon; error equation; Euler”a
equation; hydr08tatlC equation; Laplace
equation; latllude equation; length
equation; Iongltude equation: lunar
equation; normal equation; obaewatlon
●qustlon; parametric equationa;
perpendicular equation; personal
equation; elde equation; elde equation
teata.
equator ayatem—See celestial equator
eyatem ot coordinates.
equatorial axl-1. The diameter of the
Earth described between two points on the
Equator. 2. (astronomy) A telaacopa mounting
axis oriented parallel to the Earth’s rotational
axki.
equatorial bulge-The excess of the Earth’e
equatorial dtameter over the polar chameter.
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equatorial chart-1. A chart of aquatotial
areas. 2. A chatl on an equatorial pmjeCS~n.
equatorial cylindrical orthomorphlc
chart—Sac Mercator chart.
equatorial cylindrical orlhomorphlc map
projection—Sae Marcator map
projection.
equatorial diameter—Tha diameter of the
Earth at the great circle comprising the laweatrial
equator.
equatorial grevlly value-The mean
acceleration of gravity al the Equator,
approximately equal to 9.7803 rrVae~.
equetorlel horizontal parallax—The angle
at a celestial object subtended by the equatorial
semldiameter of the Earih used to indicate tha
distance of the object from the Earth.
equatorial lntewala—The englea, expreseed
in units of time, between the varbua lines which
mmpose the raticle of an astronomic transit and
the maan pesition 01 .Ihose Iinaa.
equatorial map projection—A map
projection canterad on the Equator.
equatorial node—Elrher of the two poims
whera Iha orbit o? the satellite Imer’eects Ihe
equatorial plana of its primary.
equatorial redlua-The radius aesignad to
the great circle mmprlsing lhe terrestrial
equator.
equatorial aatelllta-A satellite whose otbit
plana coincides, or almost coincides, wfth the
Earth’s equatorial plane.
equatorial etara-Stars having declinations
closa 10 zero and whose diurnal path k a
parallel of declination cbsa to the Equator.
Equalorlat stare, because o~ thalr apparently
graatar speed of lravel, are preferred for tima
and bngitude determinations.
equatorial ayatem-See celeatlal equator
ayetem of coordlnataa.
Equator—The great circle on !he Earth midway
belwean the poles and in a plane perpendicular
to the Earth’s azia of rotation. II is the line of O“