How
to do a Sun Azimuth
(Navigation Sums)
All
information from the "Norries tables" and "nautical
almanac"
|
Chronometer
time
Chronometer error .
Correct Chronometer time |
After
finding the Approximate GMT - Use the time of the chronometer (This
will be GMT but you have to work out if its GMT morning or GMT afternoon.
Also watch if a day ahead, or a day astern |
Mean
Time at ship
Longitude (arc to time)
Approximate GMT . |
|
Declination
(In Sun column under dec)
Corr (d = )
Declination |
|
GHA
Sun (In Sun column under GHA)
Increments (+)
GHA Sun
Longitude (East add) (West subtract)
LHA Sun |
|
Formula's
|
A
= Tan LAT = (Write this
number down)
Tan LHA (Store this number into the memory
of the calculator) |
The
answer to "A"
Name it opposite to latitude, unless the LHA is between 090 degrees
- 270 degrees |
B
= Tan DEC = (write this
number down)
Sin LHA (Store this number into the memory
of the calculator) |
The
answer to "B" always the same direction as the declination |
|
"C"
= "A" + "B" if both
North & North then name "C" North
"C"
= "A" + "B" if both
South & South then name "C" South
"C"
= "A" - "B" if "A"
and "B" are opposites and "A" is largest number
then name "C" what "A" is
"C"
= "B" - "A" if "A"
and "B" are opposites and "B" is largest number
then name "C" what "B" is |
Tan
Azimuth = 1 "C" Latitude Cos = Shift Tan =
True Azimuth Sun =
Compass point of "C" (Answer to
Tan Azimuth) LHA is "W" if between 000 - 180"
or "E" 180 - 360 |
|
True
bearing =
N
036 E = 036 degrees
S 036 W = 216 degrees
These
are examples |
True
Brg
Comp Brg
Comp Error
Variation
Deviation |
True
Bearing
Gyro Bearing
Gyro Error |
|
|
The
Sum should Look like This |
| |
Chronometer
time..................03.45.35
Chronometer error ................00.02.25 (fast on GMT)
Correct Chronometer time ......03.43.10 GMT
(you can't be sure yet if AM or PM) |
Mean
Time at ship ..............15.01.10
Longitude (arc to time)........00.41..00 (+) (Could
also be a minus)
Approximate GMT ................15.42.10 |
Declination
(In Sun column under dec)
Corr (d = )
Declination |
GHA
Sun (In Sun column under GHA)
Increments (+)
GHA Sun
Longitude (East add) (West subtract)
LHA Sun |
A
= Tan LAT = (Write this
number down)
Tan LHA (Store this number into the memory
of the calculator) |
B
= Tan DEC = (write this
number down)
Sin LHA (Store this number into the memory
of the calculator) |
|
"C"
= "A" + "B" if both
North & North then name "C" North
"C"
= "A" + "B" if both
South & South then name "C" South
"C"
= "A" - "B" if "A"
and "B" are opposites and "A" is largest number
then name "C" what "A" is
"C"
= "B" - "A" if "A"
and "B" are opposites and "B" is largest number
then name "C" what "B" is |
Tan
Azimuth = 1 "C" Latitude Cos = Shift Tan =
True Azimuth Sun =
Compass point of "C" (Answer to
Tan Azimuth) LHA is "W" if between 000 - 180"
or "E" 180 - 360 |
| True
bearing = 216
degrees |
True
Brg ...................216
Comp Brg..................214
Comp Error................002 East
Variation...................003 East
Deviation..................001 West |
True
Bearing...216
Gyro Bearing..218
Gyro Error ......002 Low |
