hp41programs

Phase

Phases of the Moon for the HP-41


Overview
 

-The following programs compute the date & time of a phase of the Moon that occurs near a given date.
-A few secular terms are used in the first version which is valid over the time-span [1000,3000]  ( the accuracy remains of the order of a few minutes )
-The second program uses more secular terms and an accuracy of the order of 10 minutes is achieved near 3000 B.C. ( compared to DE406/LE406 )

-See also "Eclipses for the HP-41" for a non-standard definition of the phases.
 

Program Listing1
 

Data Registers:    R00 = T = instant of the mean phase is expressed in millennia since J2000.

                               R01 = M                        where M = mean anomaly of the Sun                            R04 = phase
                               R02 = M'-180°              where M' = mean anomaly of the Moon                        R05 = 0 for a New Moon or a Full Moon, 1 otherwise
                               R03 = 1 for a Full Moon, 0 otherwise and then  2 F                                            R06 = 7.38264721 x 4k
 
                               where F = mean argument of latitude of the Moon

Flags:  none. However, set flag F04 for dates before 1582/10/15 if you use "J1" and "D1" instead of "J0" & "DT"

Subroutines:  "J0" & "DT"  ( cf "Julian & Gregorian Calendars for the HP-41" )  or "J1" & "D1" or "J2" & "D2"
                             none if you have a TIME Module, provided the dates are after 1582/10/14

-If you have a TIME Module, line 03 may be replaced by   1.012   STO 07   X<>Y   DDAYS
-In this case, key in the date in the current format:  MDY or DMY
-If you have a TIME Module, lines 148-149 may be replaced by   RCL 07   RCL Z   DATE+
 
 

  01  LBL "PHASE"
  02  DEG
  03  XEQ "J0"  
  04  7.38264721
  05  STO 06
  06  /
  07  INT
  08  STO 00
  09  ST* 06
  10  4
  11  MOD
  12  STO 04
  13  2
  14  STO 03
  15  X#Y?
  16  ST- 03
  17  ST/ 03
  18  MOD
  19  STO 05
  20  221
  21  *
  22  RCL 03
  23  -
  24  407
  25  +
  26  RCL 00
  27  49474
  28  /
  29  STO 00
  30  8
  31  %
  32  +
  33  4771976.76   
  34  +
  35  RCL 00
  36  *
  37  465
  38  SQRT
  39  +
  40  STO 02
  41  SIN
  42  *
  43  1
  44  RCL 00
  45  40
  46  /
  47  -
  48  RCL 00
  49  359989.6
  50  *
  51  13
  52  LN
  53  +
  54  STO 01
  55  SIN
  56  *
  57  172
  58  RCL 03
  59  +
  60  *
  61  +
  62  16
  63  RCL 05
  64  7
  65  *
  66  -
  67  RCL 02
  68  ST+ X
  69  SIN
  70  *
  71  +
  72  5
  73  RCL 05
  74  -
  75  ST+ X
  76  RCL 00
  77  9664016       
  78  *
  79  39
  80  -
  81  STO 03
  82  SIN
  83  *
  84  +
  85  RCL 05
  86  ST+ X
  87  7
  88  -
  89  RCL 02
  90  RCL 01
  91  -
  92  SIN
  93  *
  94  +
  95  RCL 05
  96  7
  97  *
  98  5
  99  +
100  RCL 01
101  RCL 02
102  +
103  SIN
104  *
105  +
106  RCL 01        
107  ST+ X
108  SIN
109  ST+ X
110  +
111  RCL 05
112  RCL 02
113  RCL 03
114  -
115  SIN
116  ST* Y
117  +
118  +
119  RCL 04
120  2
121  -
122  RCL 05
123  *
124  3
125  *
126  -
127  5598
128  +
129   E3
130  /
131  RCL 00
132  X^2
133  65
134  /
135  +
136  RCL 06        
137  +
138  INT
139  LASTX
140  FRC
141  X<0?
142  DSE Y
143  ""   
144  24
145  ST* Y
146  MOD
147  HMS
148  X<>Y 
149  XEQ "DT"
150  RCL 04
151  END

 
  ( 231 bytes / SIZE 007 )
 
 

      STACK        INPUTS      OUTPUTS
           Z             /      HH.MNSS
           Y             /  YYYY.MNDD
           X      yyyy.mndd        Phase

  where  yyyy.mndd  is an approximate date

               Phase = 0  for a New Moon
               Phase = 1  for a First Quarter
               Phase = 2  for a Full Moon
               Phase = 3  for a Last Quarter

  YYYY.MNDD  &  HH.MNSS  are the date & time ( in Terrestrial Time ) of the Phase

Example:

-We want to know the instant of a phase of the Moon near July 4th 2002

            2002.0704   XEQ "PHASE"  >>>>     3                                  ( Execution time = 17 seconds )
                                          RDN                2002.0702
                                          RDN                 17.2314

-There is a Last Quarter on July 2nd 2002  at 17h23 TT or 17h22 UT  ( the exact value is 17h21 UT )

-If we seek a New Moon, we can guess it happens about 7 days later,
  so we execute "PHASE" again with this new initial value:

           2002.0709    R/S       yields         0
                               RDN                 2002.0710
                               RDN                   10.2715

-The New Moon occurs on July 10th 2002 at 10h27 TT or 10h26 UT  ( the exact value )
 

Other numerical checks:
 

   1000.0101   XEQ "PHASE"    >>>>  0   RDN   1000.0109   RDN   15h32m33s  TT    ( New Moon on 1000/01/09 at 15h33 TT )
   1600.0215             R/S            >>>>  1   RDN   1600.0221   RDN     8h41m43s  TT    ( First Quarter on 1600/02/21 at 8h42 TT )
   2500.0412             R/S            >>>>  2   RDN   2500.0415   RDN   16h24m58s  TT    ( Full Moon on 2500/04/15 at 16h25 TT )
   3000.0714             R/S            >>>>  3   RDN   3000.0716   RDN   21h38m01s  TT    ( Last Quarter on 3000/07/16 at 21h38 TT )
 

-Errors can reach about 1 hour near 3000 B.C.
-Using more secular terms will increase accuracy:
 

Program Listing2
 

Data Registers:    R00 = T = instant of the mean phase    ( expressed in unit of 10000 julian years since J2000 )

                               R01 = M                        where M = mean anomaly of the Sun                            R04 = phase
                               R02 = M'-180°              where M' = mean anomaly of the Moon                        R05 = 0 for a New Moon or a Full Moon, 1 otherwise
                               R03 = 1 for a Full Moon,  0 otherwise and then  2 F                                           R06 = E
 
                               where F = mean argument of latitude of the Moon                                               R07 =  7.382647215 x 4k

Flags:  none. However, set flag F04 for dates before 1582/10/15 if you use "J1" and "D1" instead of "J0" & "DT"

Subroutines:  "J0" & "DT"  ( cf "Julian & Gregorian Calendars for the HP-41" )  or "J1" & "D1" or "J2" & "D2"
 
 

  01  LBL "PHASE"
  02  DEG
  03  XEQ "J0"
  04  7.382647215
  05  STO 07
  06  /
  07  INT
  08  STO 00
  09  ST* 07
  10  4
  11  MOD
  12  STO 04
  13  2
  14  STO 03
  15  X#Y?
  16  ST- 03
  17  ST/ 03
  18  MOD
  19  STO 05
  20  1
  21  RCL 00
  22  494740
  23  /
  24  STO 00
  25  13
  26  /
  27  .252
  28  +
  29  RCL 00
  30  *
  31  -
  32  STO 06
  33  13
  34  LN
  35  RCL 00
  36  X^2
  37  9
  38  /
  39  3599896       
  40  -
  41  RCL 00
  42  *
  43  -
  44  STO 01
  45  ST+ X
  46  SIN
  47  ST+ X
  48  *
  49  RCL 01
  50  SIN
  51  172
  52  RCL 03
  53  +
  54  *
  55  +
  56  465
  57  SQRT
  58  RCL 00
  59  5.8
  60  *
  61  12.38
  62  -
  63  RCL 00
  64  *
  65  6164
  66  D-R
  67  -
  68  RCL 00
  69  *
  70  47719767.64
  71  -
  72  RCL 00
  73  *
  74  -
  75  STO 02
  76  RCL 01
  77  -
  78  SIN
  79  RCL 05
  80  ST+ X
  81  7
  82  -
  83  *
  84  +
  85  RCL 05
  86  7
  87  *
  88  5
  89  +
  90  RCL 01
  91  RCL 02        
  92  +
  93  SIN
  94  *
  95  +
  96  RCL 06
  97  *
  98  RCL 05
  99  221
100  *
101  RCL 03
102  -
103  407
104  +
105  RCL 02
106  SIN
107  *
108  +
109  16
110  RCL 05
111  7
112  *
113  -
114  RCL 02
115  ST+ X
116  SIN
117  *
118  +
119  RCL 00
120  ST+ X
121  5
122  -
123  RCL 00
124  X^2
125  *
126  96640162     
127  +
128  RCL 00
129  *
130  39
131  -
132  STO 03
133  SIN
134  5
135  RCL 05
136  -
137  ST+ X
138  *
139  +
140  RCL 05
141  RCL 02
142  RCL 03
143  -
144  SIN
145  ST* Y
146  +
147  +
148  RCL 04
149  2
150  -
151  RCL 05
152  *
153  3
154  *
155  -
156  5598
157  +
158  73
159  RCL 00
160  *
161  150
162  -
163  RCL 00        
164  *
165  1544
166  +
167  RCL 00
168  X^2
169  *
170  +
171   E3
172  /
173  RCL 07
174  +
175  INT
176  LASTX
177  FRC
178  X<0?
179  DSE Y
180  ""   
181  24
182  ST* Y
183  MOD
184  HMS
185  X<>Y
186  XEQ "DT"
187  RCL 04
188  END

 
   ( 289 bytes / SIZE 008 )
 
 

      STACK        INPUTS      OUTPUTS
           Z             /      HH.MNSS
           Y             /  YYYY.MNDD
           X      yyyy.mndd        Phase

  where  yyyy.mndd  is an approximate date

               Phase = 0  for a New Moon
               Phase = 1  for a First Quarter
               Phase = 2  for a Full Moon
               Phase = 3  for a Last Quarter

   YYYY.MNDD  &  HH.MNSS  are the date & time ( in Terrestrial Time ) of the Phase

Example:

  -3101.0210      XEQ "PHASE"      returns:                                    ---Execution time = 20s---

                            0                          A New Moon occured
       RDN    -3101.0217                     on  -3101/02/17                        Julian Calendar             ( -3101 = 3102 B.C. )
       RDN         22.5512                      at    22h55m  TT

Notes:

-All results are expressed in Terrestrial Time. The difference TT - UT can be approximated by a formula given by Morrison & Stephenson:
  TT - UT ( in seconds ) = -15 + ( 32.5 +/- 2 ).( t - 0.1 )2  where t is measured in centuries from AD 1800.

-Many other periodic terms are given in "Astronomical Algorithms"
 

Reference:

[1]  Jean Meeus , "Astronomical Algorithms" - Willmann-Bell  -  ISBN 0-943396-61-1