An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

Angle of incidence of light proceeding from a denser medium toward a thinner, at which grazing refraction occurs (angle of refraction 90°).

→ critical; → angle.

1) The angle by which a light ray is curved by the gravitational field of a massive body. Einstein's general relativity predicts that a light ray which tangentially grazes the surface of the Sun is deflected by 1''.7. This result was confirmed in 1919 when the apparent angular shift of stars close to the limb of the Sun was measured during a total solar eclipse.
2) In a cathode-ray tube, the angle through which the beam is bent, vertically, horizontally, or diagonally.

→ deflection; → angle.

An angle formed by two planes meeting along a common line. Compare with → face angle.

→ angle; → dihedral.

The angular difference between the → visible horizon and the → true horizon. Same as → dip of the horizon.

→ dip; → angle.

An angle made by a given vector and a coordinate axis.
The angle between the North and a chosen direction.

→ direct; → angle.

To wrap or twist together; to intertwine.

From → en- "in," + tangle, from M.E. tangilen, tagilen "to entangle."

Hamgureš, from ham- "together," → com-, + guridan "to become tangled, as threads or hairs, entwine," probably related to greh "knot," → node.
Hampicidan, from ham- + picidan "to twist, entwine, coil."

The act of entangling. The state of being entangled.

Verbal noun of → entangle; → -ment.

Same as the → initial phase angle.

→ epoch; → angle.

A triangle having three equal sides.

→ equi-, → lateral, → triangle.

Sé-pahlu-barâbar, from sé, → three, pahlu, → side, barâbar, → equal.

1) Any of the four angles that do not include a region of the space between two lines intersected by a third straight line (→ transversal).
2) The angle between any side and an extension of an adjacent side of a polygon.

→ exterior; → angle.

An angle formed by any two adjacent edges of a → polyhedron, in contrast to a → dihedral angle.

→ face; → angle.

The angle between the incident optical beam and the normal to the grating. It is the angle to which the grating must be set to place the desired wavelength at the center of the detector.

→ grating; → angle.

A telescope based coordinate specifying the angle, in the equatorial plane, from the meridian to a plane containing the celestial object and the north and south celestial poles.

→ hour; → angle.

Same as → angle of incidence.

→ incidence; → angle.

The value of the phase corresponding to the origin of time. Same as the → epoch angle.

→ initial; → phase; → angle.

An angle whose vertex lies on a circle and whose sides are chords of the circle.

Inscribed p.p. of → inscribe; → angle.

1) Any of the four angles formed between two straight lines intersected by a third straight line (→ transversal).
2) The angle between two adjacent sides of a polygon that lies inside the polygon.

→ interior; → angle.

Adaptive optics: The angle over which wavefront phases become de-correlated by 1 radian rms due to → tip-tilt alone. It is defined analogously to the → isoplanatic angle.

→ iso-; → kinetic; → angle.

The angle in which the → point spread function of the atmosphere/telescope system is space invariant. Because of the presence of → turbulence in high layers of the atmosphere, this angle is extremely small, often only a few seconds of arc at visible wavelengths. See also → aplanatism.

→ isoplanatic; → angle.

A triangle having two sides equal.

From L.L. isosceles, from Gk. isoskeles "with equal legs; that can be divided into two equal parts," from isos "equal, identical," → iso-, + skelos "leg."

Sebar, → triangle, do-pahlu-baraabar, from do, → two, pahlu, → side, barâbar, → equal.