Transcript 109654.briseset

SUN RISE AND SET.
{Numbers are places to go to on the Diagram.}
The important SUN is our light provider. The SUN
while below our horizon give us various stages of
light . Stages are listed in the NAUTICAL ALMANAC
as twilight, incomplete darkness. The stages are
Civil, can see the horizon, with our Sun 6 degrees
below our horizon. NAUTICAL, dim horizon at 12
degrees, and ASTRONOMICAL little to no horizon.
The SUN travel upward toward the horizon can be
considered one degree in 4 minutes. Of great
important is SUN RISE, and SUNSET. In these cases
our SUN upper limb is on the horizon.
The Astronomer can demonstrate and visually
show the mechanics and readable TIME, HIEGHT
and bearing of these important facts.
After marking the STAR DISK with the SUN’S DEC
and GHA. {1} Rotate the mock SUN toward the
EAST horizon, touching it. Read the GMT time off
the BASE RIM. {2} Do the same for SUNSET.
The GMT reading for only the sun can be a line
passing from the center pin, through the sun to the
outer rim or Aries reading – month and day time.
Example 45N 75W JULY 25.
1. Sunrise 072 @ 10:08. 2. Sunset 288 @ 23:52.
These are estimated bearings and Times, but are
close to computed, book values.
The sun could be further corrected 3 minutes for
rise - earlier or set + later for refraction and upper
limb.
{1}
{2}