Hi. I'm looking for a program that can give me the position of the sun in RA and DEC for a HP-41CX with the curent date and time of the calculator.

Or at least an algorithm that will help me do the program... I just buy a 11" celestron for school with a "GO TO" for 40 000 objects in the sky BUT the sun has not been program and it is often difficult to point correctly the sun. But with RA and DEC from my CX i will just enter them and GOTO!

Thanks
Michel Beaulieu
Canada

Michel --

I have a program written by Tom Sherman in 1986, which he sent to me within the past several years. It requires an HP-41 Navigation Pac and a 41CX or 41C/CV with Time Module. (A 41C will also require a Memory Module or Quad Memory Module.)

Given the latitude and longitude of a location, plus the date and time from the clock, it will calculate the angles of altitude and azimuth for the sun, the moon, four visible planets, and many navigational stars.

I'd like to make a few refinements to the program, but have not yet done so. I have written the program to magnetic cards.

-- KS

I know it may seem redundant, however one must be extremely careful when viewing the sun. You MUST have a solar filter that is compatable with your telescope!

tm

Here is a BASIC program which will give the RA and DEC of the Sun to very high accuracy (a few seconds of arc) given year, date, and time (hours and minutes) as input. (Note, there are some extra variables printed in this version - helpful for debugging and generally checking what's happening). Note that the parallax of the Sun (which can be up to almost 10 arcseconds) is ignored. The RA, DEC are with respect to the center of the Earth. RA and DEC are in fractional hours and degrees - I'm not sure what your telescope wants.

10 DEFDBL A-H,J-Z

20 PI = 3.14159265#: TWOPI = 2# * PI: CONV = TWOPI / 360#

30 YEAR = 2000: MONTH = 8: DAY = 22: HOUR = 2: MIN = 0

     get the time & date from the calculator instead

40 UTC = (TWOPI * (60# * HOUR + MIN)) / 1440#

50 DIM NDAY(12)

60 DATA 0,31,59,90,120,151,181,212,243,273,304,334

70 FOR I = 1 TO 12

80 READ NDAY(I)

90 NEXT I

100 YEARM = YEAR - 1900#

110 KDAY = INT((YEARM - 1#) / 4#)

120 JULDAY = 2415019.5# + YEARM*365# + KDAY

130 JULDAY = JULDAY + NDAY(MONTH) + DAY

140 IF(YEARM/4# - INT(YEARM/4#)) > .2 THEN GOTO 160

150 IF(MONTH > 2) THEN JULDAY = JULDAY + 1#

160 CENTURY = ( JULDAY - 2451545# ) / 36525#

170 STM = 24110.55# + CENTURY* (8640184.812866# + .093104#*CENTURY)

180 STM = STM/86400# - INT(STM/86400#)

190 STM = 2# * PI * STM: PRINT JULDAY,STM*12/PI

200 DAYS = JULDAY - 2451545# + (UTC/TWOPI)

210 SOLLON = 280.46# + .9856474# * DAYS

220 SOLLON = SOLLON - 360# * SGN(SOLLON)*INT(SOLLON/360#)

230 IF(SOLLON < 0) THEN SOLLON = SOLLON + 360#

240 SOLANOM = 357.528# + .9856003# * DAYS

250 SOLANOM = SOLANOM * CONV

260 SOLANOM = SOLANOM + TWOPI * SGN(SOLANOM)*INT(SOLANOM/TWOPI)

270 IF(SOLANOM < 0) THEN SOLANOM = SOLANOM + TWOPI

280 ECLLON = SOLLON + 1.915# * SIN(SOLANOM) + .02# * SIN(2#*SOLANOM)

290 ECLLON = ECLLON * CONV

300 ECLLON = ECLLON + TWOPI * SGN(ECLLON)*INT(ECLLON/TWOPI)

310 QUADRANT = ECLLON / (PI/2)

320 IQUAD = 1 + INT(QUADRANT)

325 PRINT ECLLON,QUADRANT,IQUAD

330 OBLIQ = 23.439# - .0000004# * DAYS

340 OBLIQ = OBLIQ * CONV

350 RA = ATN( COS(OBLIQ) * TAN(ECLLON) )

360 IF IQUAD=2 THEN RA = RA + PI

370 IF IQUAD=3 THEN RA = RA + PI

380 IF IQUAD=4 THEN RA = RA + TWOPI

390 ARG = SIN(OBLIQ) * SIN(ECLLON)

400 DEC = ATN(ARG/SQR(1-ARG*ARG)): PRINT RA*12/PI,DEC/CONV

I wrote this as part of the SUNMOON program which was published with my article on calibrating antennas by observing the Sun or Moon in the ARRL UHF/VHF Handbook. It uses a formula from the "American Ephemeris and Nautical Almanac" (published by the US Navy).

If you have questions, you can e-mail me directly.

Dave W8MIF

I have a Meade ETX90 and the SUN is not in the controller either, and safety is the main reason for that. The trick I know that has been used is to define a planetary object (if that is possible) that has the same orbit as the earth, but exactly opposite of the sun.

Be very very careful with solar watching. Use a good solar filter!

Hello Michel!

Something to try!
I wrote this program for my 41cv.

Good luck!

Wilhelm Loidl

p.s.: sorry for the format!

LBL "SUN"
FIX 04
CF 01
XEQ 07
LBL 24
XEQ 08
CLA
"? GMT HR.MIN"
PROMPT
HR
LBL 15
15
*
STO 02
STO 05
RCL 03
+
365.25
/
118.1
RCL 04
968
/
-
+
.2
P-R
9.58
-
*
+
RCL 04
427
/
RCL 04
COS
-
8531.5
-
360
/
CHS
X<>Y
-1
P-R
RDN
P-R
R^
R-P
RDN
X<>Y
STO 07
ASIN
STO 06
RDN
-
ST+ 05
RCL 05
RCL 00
-
RCL 06
COS
P-R
RCL 01
STO 06
X<>Y
P-R
X<> 06
RCL 07
P-R
X<> 06
+
ASIN
X<> 06
-
R-P
RDN
180
+
STO 08
FS? 01
RTN
CLA
"HRZ "
ARCL X
AVIEW
PROMPT
CLA
"VRT "
ARCL 06
AVIEW
PROMPT
GTO 24
RTN
LBL 07
"LAT ?"
CLA
"? LAT N+ DEG"
PROMPT
STO 01
"? LNG W+ DEG"
PROMPT
STO 00
RTN
LBL 08
CLA
"? MM.DDYYYY"
PROMPT
INT
STO 06
LASTX
FRC
100
*
INT
STO 03
LASTX
FRC
1 E4
*
X<> Z
3056
%
INT
ST+ 03
R^
STO 04
RCL 06
3
X>Y?
1
RCL 04
4
/
FRC
+
1
X<>Y
X=Y?
2
RCL 04
7
-
RCL 03
365.25
/
+
STO 06
20
*
STO 04
SIN
4
*
50941
+
RCL 06
7
*
+
896
/
-
ST- 03
360
ST* 03
RTN

Thanks for the BASIC and the HP-41 program, i'm just entering them in my 41c and my 75c.

Michel

Hi,
You can use the program listed in the HP-41 software library:
"Astronomical Ephemeris"
Regards
JM

Like this?

001 *LBL "SUN" 

002  FIX 04

003  CF 01

004  XEQ 07 

005  LBL 24 

006  XEQ 08 

007  CLA

008  '? GMT HR.MIN' 

009  PROMPT

010  HR

011  LBL 15 

012  15

013  *

014  STO 02

015  STO 05

016  RCL 03

017  +

018  365.25

019  /

020  118.1

021  RCL 04

022  968

023  /

024  -

025  +

026  .2

027  P-R

028  9.58

029  -

030  *

031  +

032  RCL 04

033  427

034  /

035  RCL 04

036  COS

037  -

038  8531.5

039  -

040  360

041  /

042  CHS

043  X<>Y

044  -1

045  P-R

046  RDN

047  P-R

048  R^

049  R-P

050  RDN

051  X<>Y

052  STO 07

053  ASIN

054  STO 06

055  RDN

056  -

057  ST+ 05

058  RCL 05

059  RCL 00

060  -

061  RCL 06

062  COS

063  P-R

064  RCL 01

065  STO 06

066  X<>Y

067  P-R

068  X<> 06

069  RCL 07

070  P-R

071  X<> 06

072  +

073  ASIN

074  X<> 06

075  -

076  R-P

077  RDN

078  180

079  +

080  STO 08

081  FS? 01

082  RTN 

083  CLA

084  'HRZ ' 

085  ARCL X

086  AVIEW

087  PROMPT

088  CLA

089  'VRT '

090  ARCL 06

091  AVIEW

092  PROMPT

093  GTO 24 

094  RTN 

095  LBL 07 

096  'LAT ?' 

097  CLA

098  '? LAT N+ DEG' 

099  PROMPT

100  STO 01

101  '? LNG W+ DEG' 

102  PROMPT

103  STO 00

104  RTN 

105  LBL 08 

106  CLA

107  '? MM.DDYYYY' 

108  PROMPT

109  INT

110  STO 06

111  LASTX

112  FRC

113  100

114  *

115  INT

116  STO 03

117  LASTX

118  FRC

119  1 E4

120  *

121  X<> Z

122  3056

123  % 

124  INT 

125  ST+ 03

126  R^ 

127  STO 04

128  RCL 06

129  3 

130  X>Y?

131  1 

132  RCL 04

133  4 

134  / 

135  FRC

136  + 

137  1 

138  X<>Y

139  X=Y?

140  2 

141  RCL 04

142  7 

143  -

144  RCL 03 

145  365.25

146  / 

147  + 

148  STO 06

149  20 

150  * 

151  STO 04

152  SIN 

153  4 

154  * 

155  50941 

156  + 

157  RCL 06

158  7 

159  * 

160  + 

161  896 

162  / 

163  -

164  ST- 03

165  360 

166  ST* 03

167  RTN

Thanks; with that form i was able to track my error on line 044 -1 i entered 044 - and 045 1. Now the program works great.

By the way, is there a program to convert these coordinate to equatorial one?

Thanks again
Michel

The Sokkia company, a manufacturer of surveying equipment, publishes an annual pocket-sized "Celestial Observation Handbook & Ephemeris" for surveyors. It traditionally included professional-grade HP calculator programs for the 41, 42 and 48 series. I haven't seen the latest editions and don't know if the programs are still there; they were in the 2003 edition.

You can find this at surveying supply stores or www.forestry-suppliers.com if interested. It costs about $8.50.

The Sokkia book and programs were written by Elgin, Knowles & Senne, at http://www.rollanet.org/~eksi/softprod.htm . They apparently still offer the "Astro*Card" for HP48GX.