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MOON AZ-EL ROUTINE FOR HP45
Allowing for Parallax
(May also be used for Great Circle bearing and distance calculations)
G.D. Wall ZE2KV

"Moon Az-El Calculations
Preliminary:
(a) Longitude to STO 1 (degrees and decimals).
Longitude East positive, West negative.
(b) Colatitude for North elevated pole to STO 2 (degrees and decimals).
Colat for northern latitudes = 90 - Lat
Colat for southern latitudes = 90 + Lat
(c) Horizontal Parallax to STO 3 (degrees and decimals). Obtain from the Nautical Almanac
Routine:
Read in GHA (DMS)
DMS+
RCL 1
+ *Note if less than 360
COS
RCL 2
SIN
STO 4
×
90
ENTER Read in DEC (DMS} North positive South negative
DMS→
STO 5
SIN
×
RCL 2
COS
STO 6
RCL 5
COS
STO 5
×
+
ENTER
COS⁻¹
ENTER
(STO 8)
SIN
STO 7
RCL 3
×
+
CHS
90
x⇄y
RCL 6
×
CHS
RCL 5
+
RCL 4
RCL 7
×
COS⁻¹ If less than 360 Read Azimuth otherwise proceed
CHS
360

At Test Point * less than 360 means values of 180 through
270 to 360, and negative values through -90 to -180

Test:
Location 36°-45'-40" N; 119°-47'-10" W
Horizontal Parallax 56.4'
GHA 85°-33.6'
Declination 13°-21.2' S
Elevation 29.61°
Azimuth 140.61°

Great Circle calculations:
1. Home station data is entered into STO 1 and STO 2 as before. STO 3 is zero.
2. Enter the longitude of the distant point at GHA but with
reversed sign, i.e., Long 120 W = 120 Long 50 E = -50
3. Enter the latitude of the distant point at DEC. Positive for North latitudes, negative for South.
4. Great Circle angular distance is stored at STO 8 for future use.
5. Bearing of the distant station is read at Azimuth.
6. Great Circle distance is then obtained:
RCL 8
69.057
× Read (in miles)
RCL 8
111.14
× Read (in kilometers)
7. Part of the parallax correction routine is not used in the Great Circle calculations and may be omitted. Miss out the steps (RCL 3 ..... .. Read Elevation x-y) but roll down twice after STO 7 and before RCL 6.
Test:
Fresno 36°-45'-40" N; 119°-47'-10" W
to Salisbury, Rhodesia
18°S; 31°E