thesky_sun Module Reference

Low-accuracy procedures for the Sun. More...

Functions/Subroutines
subroutine	sunpos_la (jd, calc, lat, lon)
	Low-accuracy solar coordinates.
subroutine	sunpos_vla (doy, hour, lon, lat, tz, ha, dec, az, alt)
	Compute the position of the Sun - very low accuracy routine (~0.18 degrees in az/alt)
real(double) function	sunmagn (dist)
	Calculate Sun magnitude.

Detailed Description

Low-accuracy procedures for the Sun.

Function/Subroutine Documentation

sunmagn()

real(double) function thesky_sun::sunmagn

(

real(double), intent(in)

dist

)

Calculate Sun magnitude.

Parameters

dist	Distance (AU)

Return values

sunmagn

Sun magnitude

Definition at line 282 of file sun.f90.

References sunmagn().

Referenced by thesky_planets::planet_position(), sunmagn(), and sunpos_la().

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sunpos_la()

subroutine thesky_sun::sunpos_la	(	real(double), intent(in)	jd,
		integer, intent(in)	calc,
		real(double), intent(in), optional	lat,
		real(double), intent(in), optional	lon )

Low-accuracy solar coordinates.

Parameters

jd	Julian Day of computation
calc	Calculate: 1: l,b,r, 2: & ra,dec, 3: & gmst,agst, 4: & az,alt, 5: & mag + p.a., 99: & topo alt + refraction
lat	Latitude of the observer (rad, optional)
lon	Longitude of the observer (rad, optional)

Note

• accuracy: ~0.01°; ~0.0033° when comparing ecliptical coordinates to VSOP87 for 1900-2100 (10^5 random instances)
• for 1900-2100, the terms greater than Tjc^2 can be neglected without loss of accuracy

• lat0 and lon0 can be provided through the module TheSky_local (rad, rad), or through the optional arguments. Note that using the latter will update the former!
• results are returned in the array planpos() in the module TheSky_planetdata

See also

• Chapront-Touze, Chapront, A&A, 190, p.342, 1988, Table 6 (CTC88)
• Explanatory Supplement to the Astronimical Almanac (3rd Ed, 2012)
• Meeus, Astronomical Algorithms, 1998, Ch.25
• Simon et al, A&A, 282, p.663 (1994)

Todo

odot is off by ~10" (~0.003d) in Meeus, Example 25a. Would need better L0 or C (or M?)

Definition at line 57 of file sun.f90.

References thesky_datetime::calc_deltat(), thesky_datetime::calc_gmst(), thesky_coordinates::eq2horiz(), thesky_local::lat0, thesky_local::lon0, thesky_planetdata::planpos, thesky_coordinates::refract(), and sunmagn().

Referenced by thesky_moon::moonpos_la(), and thesky_planets::planet_position_la().

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sunpos_vla()

subroutine thesky_sun::sunpos_vla	(	integer, intent(in)	doy,
		real(double), intent(in)	hour,
		real(double), intent(in)	lon,
		real(double), intent(in)	lat,
		real(double), intent(in)	tz,
		real(double), intent(out)	ha,
		real(double), intent(out)	dec,
		real(double), intent(out)	az,
		real(double), intent(out)	alt )

Compute the position of the Sun - very low accuracy routine (~0.18 degrees in az/alt)

Parameters

DoY	Day of year
hour	Hour of day
lon	Geographic longitunde (radians; >0=east)
lat	Geographic latitunde (radians; >0=north)
tz	Time zone (hours; >0=east)
ha	Hour angle of the Sun (radians) (output)
dec	Declination of the Sun (radians; >0=north) (output)
az	Azimuth of the Sun (radians; 0=north, pi/2=east) (output)
alt	Altitude of the Sun (radians; >0 = up) (output)

See also

Wenham, S.R.: Applied photovoltaics (2012; book), Appendix B

Definition at line 225 of file sun.f90.