(25) Celestial Azimuth / Elevation (ARRL)

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An excerpt from the ARRL Handbook for radio amateurs, Azimuth and Elevation, 1991, page 23-37 & 23-38 {639-640}

" Calculator and Computer Programs
  As has been mentioned, a calculator or computer may be used in solving the equations for azimuth and elevation. Tables in this section list suitable programs. The program of Table 9 is for Hewlett-Packard HP-25 and similar calculators using reverse Polish notation (RPN). With this program, the GHA and declination of a celestial body are entered for a particular time of day, and the calculator computes the azimuth and elevation for that time. Calculations must then be repeated for a different time of day, by using different GHA and declination values, as appropriate. For EME work, it is convenient to calculate ez-al data at 30-minute intervals or so, and to keep the results of all calculations handy during the EME window. Necessary antenna-position corrections can then be made periodically. "

Table 9
Calculator Program for Determining
Azimuth and Elevation of Celestial
Bodies

Code:

Line  Key Entry
01    RCL 1
02    -
03    STO 4
04    f COS
05    X↔Y
06    STO 5
07    f COS
08    ×
09    RCL 0
10    f COS
11    STO 6
12    ×
13    RCL 0
14    f SIN
15    STO 7
16    RCL 5
17    f SIN
18    STO 5
19    ×
20    +
21    STO × 7
22    ENTER ↑
23    g SINˉ¹
24    f COS
25    STO × 6

      use these program steps for the moon
26    g ¹⁄ₓ
27    X↔Y
      use these program steps for the sun and distant bodies
26    f Last X
27    GTO 32

28    RCL 3
29    -
30    ×
32    g TANˉ¹
32    RCL 5
33    RCL 7
34    -
35    RCL 6
36    ÷
37    g COSˉ¹
39    RCL 4
39    f SIN
40    g X ≥ 0
41    GTO 44
42    R ↓
43    GTO 00
44    R ↓
45    CHS
46    RCL 2
47    +
48    GTO 00

" Instructions
    1) Load the program, selecting lines 26 and 27 for either the moon or for more distant bodies. Switch to RUN.
    2) Initialize: f PRGM; f FIX 1; g DEG
    3) Store constants: 360 STO 2; 0.01657 STO 3
    4) Store data:
        your latitude (degrees and decimal; negative if east) STO 0
        your longitude (degrees and decimal; negative if east) STO 1
    5) Input data:
        Decl. of celestial body (degrees and decimal) Enter ↑
        GHA of celestial body (degrees and decimal) R/S
        The result displayed after a few seconds is the azimuth or bearing in degrees clockwise from north.
        Depressing X↔Y displays the elevation angle above the horizon. (The body is below the horizon if a negative angle is displayed.)
    6) For another az-el calculation from the same location, go to step 5.
    7) For az-el calculations from a different location on the earth's surface, go to step 4 using new latitude and longitude. "

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