Distance in the heavens is measured in Right Ascension or Oblique Ascension, or along the
Ecliptic, the Equator, or the Prime Vertical, in (1) Sidereal hours and minutes of Right
Ascension along the Equator; (2) degrees and minutes of arc of Oblique Ascension along the
Ecliptic, and in degrees and minutes of arc of declination above or below the Equator, or of
latitude above or below the Ecliptic.
Polar Distance. The angular distance of a celestial object from the pole: 90° minus the
declination.
Actual Intra-solar system distances are expressed in astronomical Units (q. v.): Ultra-solar
system distances in Light Years (q. v.).
Diurnal. Of or belonging to the day: as the apparent diurnal motion of the planets resulting from
the axial rotation of the Earth (v. Motion).
D. Arc: Measurement, in degrees, of the arc a celestial body traverses from its rising to its
setting.
D. Houses. v. Houses, Rulers of.
D. Planets. v. Planets.
D. Ruler, that which rules by day.
D. Triplicities: the Fire Trigon for the Sun; and so on.
v. Dignities: Rulers of the Triplicities.
Dog Days. A forty-day period extending from July 4 to August 11; given by some authorities as
from July 20th to August 27. It was considered by the ancients to be the hottest period of the
year. They reckoned the commencement from the heliacal rising of Sirius (the Dog Star). Hesiod
placed the ending of the period at 50 days after the Summer solstice. Mars, the planet associated
with heat, conjoined Sirius during the serious drought and hot spell of mid-July 1937.
Dog Stars. Sirius and Procyon. v. Stars.Domal Dignity. Said of a planet when it tenants its own Sign (v. Rulers.) A planet so placed
was described by the ancients as 'domiciliated'.Dominical Letter. Literally, the "Sunday" letter. To connect a week day with a day of the year,
January 1 is A; 2, B; 3, C; 4, D; 5, E; 6, F; 7, G. Thus 8 becomes A, and so on. However, if one
says that the Dominical letter is C then January 1 of that year will fall upon Friday. Its chief use
is in connection with an involved system for determining the date upon which will fall the