;------------------------------------------------------------- ;+ ; NAME: ; SUNJS ; PURPOSE: ; Computes geocentric physical ephemeris of the sun. ; CATEGORY: ; CALLING SEQUENCE: ; sunjs, js ; INPUTS: ; js = ephemeris time as Julian Seconds. in ; Delta T = ET - UT which is not completely ; predictable but is about 1 minute now. ; This difference is noticable slightly. ; KEYWORD PARAMETERS: ; Keywords: ; /LIST displays values on screen. ; DIST = distance in AU. ; SD = semidiameter of disk in arc seconds. ; TRUE_LONG = true longitude (deg). ; TRUE_LAT = 0 always. ; APP_LONG = apparent longitude (deg). ; APP_LAT = 0 always. ; TRUE_RA = true RA (hours). ; TRUE_DEC = true Dec (deg). ; APP_RA = apparent RA (hours). ; APP_DEC = apparent Dec (deg). ; LAT0 = latitude at center of disk (deg). ; LONG0 = longitude at center of disk (deg). ; PA = position angle of rotation axis (deg). ; CARRINGTON = Carrington rotation number. ; OUTPUTS: ; COMMON BLOCKS: ; NOTES: ; Notes: based on the book Astronomical Formulae ; for Calculators, by Jean Meeus. ; If no arguments given will prompt and list values. ; MODIFICATION HISTORY: ; R. Sterner, 1995 Dec 13 ; ; Copyright (C) 1995, Johns Hopkins University/Applied Physics Laboratory ; This software may be used, copied, or redistributed as long as it is not ; sold and this copyright notice is reproduced on each copy made. This ; routine is provided as is without any express or implied warranties ; whatsoever. Other limitations apply as described in the file disclaimer.txt. ;- ;------------------------------------------------------------- pro sunjs, js, help=hlp, $ dist=dist, true_long=true_long, app_long=app_long, $ true_lat=true_lat, app_lat=app_lat, sd=sd, $ true_ra=true_ra, app_ra=app_ra, true_dec=true_dec, $ app_dec=app_dec, pa=pa, lat0=lat0, long0=long0, list=list, $ carrington=carr np = n_params(0) if keyword_set(hlp) then begin print,' Computes geocentric physical ephemeris of the sun.' print,' sunjs, js' print,' js = ephemeris time as Julian Seconds. in' print,' Delta T = ET - UT which is not completely' print,' predictable but is about 1 minute now.' print,' This difference is noticable slightly.' print,' Keywords:' print,' /LIST displays values on screen.' print,' DIST = distance in AU.' print,' SD = semidiameter of disk in arc seconds.' print,' TRUE_LONG = true longitude (deg).' print,' TRUE_LAT = 0 always.' print,' APP_LONG = apparent longitude (deg).' print,' APP_LAT = 0 always.' print,' TRUE_RA = true RA (hours).' print,' TRUE_DEC = true Dec (deg).' print,' APP_RA = apparent RA (hours).' print,' APP_DEC = apparent Dec (deg). print,' LAT0 = latitude at center of disk (deg).' print,' LONG0 = longitude at center of disk (deg).' print,' PA = position angle of rotation axis (deg).' print,' CARRINGTON = Carrington rotation number.' print,' Notes: based on the book Astronomical Formulae' print,' for Calculators, by Jean Meeus.' print,' If no arguments given will prompt and list values.' return endif ;---------------------------------------------------; ; Interactive mode ; ;---------------------------------------------------; if np eq 0 then begin print,' ' print,' Compute Sun parameters' print,' ' txt = '' read,' Ephermeris date and time: ',txt if txt eq '' then return js = dt_tm_tojs(txt) list = 1 endif ;---------------------------------------------------; ; Convert js to y,m,d,et ; ;---------------------------------------------------; js2ymds,js,yr,m,d,s et = s/3600. ;---------------------------------------------------; ; Radians/degrees conversion (double) ; ;---------------------------------------------------; radeg = 180.d0/!dpi ;---------------------------------------------------; ; Julian Date ; ;---------------------------------------------------; jd = double(ymd2jd(yr, m, d)) - 0.5d0 + et/24d0 ;---------------------------------------------------; ; Julian Centuries from 1900.0 ; ;---------------------------------------------------; t = (jd - 2415020d0)/36525d0 ;---------------------------------------------------; ; Carrington Rotation Number. ; ;---------------------------------------------------; carr = (1./27.2753D0)*(jd-2398167.d0) + 1.d0 ;---------------------------------------------------; ; Geometric Mean Longitude (deg) ; ;---------------------------------------------------; mnl = 279.69668d0 + 36000.76892d0*t + 0.0003025*t^2 mnl = mnl mod 360d0 ;---------------------------------------------------; ; Mean anomaly (deg) ; ;---------------------------------------------------; mna = 358.47583d0 + 35999.04975d0*t - $ 0.000150d0*t^2 - 0.0000033d0*t^3 mna = mna mod 360d0 ;---------------------------------------------------; ; Eccentricity of orbit ; ;---------------------------------------------------; e = 0.01675104d0 - 0.0000418d0*t - 0.000000126d0*t^2 ;---------------------------------------------------; ; Sun's equation of center (deg) ; ;---------------------------------------------------; c = (1.919460d0 - 0.004789d0*t - 0.000014d0*t^2)*sin(mna/radeg) $ + (0.020094d0 - 0.000100d0*t)*sin(2*mna/radeg) $ + 0.000293d0*sin(3*mna/radeg) ;---------------------------------------------------; ; Sun's true geometric longitude (deg) ; ; refered to the mean equinox of date. ; ; Should the higher accuracy terms (not ; ; included here) be added to true_long? ; ; (from which app_long is derived). ; ;---------------------------------------------------; true_long = (mnl + c) mod 360d0 ;---------------------------------------------------; ; Sun's true anomaly (deg) ; ;---------------------------------------------------; ta = (mna + c) mod 360d0 ;---------------------------------------------------; ; Sun's radius vector (AU) ; ; There are a set of higher accuracy ; ; terms not included here. The values ; ; calculated here agree with the example ; ; in the book. ; ;---------------------------------------------------; dist = 1.0000002d0*(1.d0 - e^2)/(1.d0 + e*cos(ta/radeg)) ;---------------------------------------------------; ; Semidiameter (arc sec) ; ;---------------------------------------------------; sd = 959.63/dist ;---------------------------------------------------; ; Apparent longitude (deg) from true ; ; longitude. ; ;---------------------------------------------------; omega = 259.18d0 - 1934.142d0*t ; Degrees app_long = true_long - 0.00569d0 - 0.00479d0*sin(omega/radeg) ;---------------------------------------------------; ; Latitudes (deg) for completeness. ; ; Never more than 1.2 arc sec from 0, ; ; always set to 0 here. ; ;---------------------------------------------------; true_lat = 0. app_lat = 0. ;---------------------------------------------------; ; RA, Dec ; ;---------------------------------------------------; ;---------------------------------------------------; ; True Obliquity of the ecliptic (deg) ; ;---------------------------------------------------; ob1 = 23.452294d0 - 0.0130125d0*t - 0.00000164d0*t^2 $ + 0.000000503d0*t^3 ;---------------------------------------------------; ; True RA, Dec (is this correct?) ; ;---------------------------------------------------; y = cos(ob1/radeg)*sin(true_long/radeg) x = cos(true_long/radeg) recpol, x, y, r, true_ra, /deg true_ra = true_ra mod 360d0 if true_ra lt 0. then true_ra = true_ra + 360d0 true_ra = true_ra/15d0 true_dec = asin(sin(ob1/radeg)*sin(true_long/radeg))*radeg ;---------------------------------------------------; ; Apparent RA, Dec ; ; Agrees with example in book. ; ;---------------------------------------------------; ;---------------------------------------------------; ; Apparent Obliquity of the ecliptic ; ;---------------------------------------------------; ob2 = ob1 + 0.00256d0*cos(omega/radeg) ; Correction. y = cos(ob2/radeg)*sin(app_long/radeg) x = cos(app_long/radeg) recpol, x, y, r, app_ra, /deg app_ra = app_ra mod 360d0 if app_ra lt 0. then app_ra = app_ra + 360d0 app_ra = app_ra/15d0 app_dec = asin(sin(ob2/radeg)*sin(app_long/radeg))*radeg ;---------------------------------------------------; ; Heliographic coordinates ; ;---------------------------------------------------; theta = (jd - 2398220d0)*360d0/25.38d0 ; Deg. i = 7.25 ; Deg. k = 74.3646 + 1.395833*t ; Deg. lamda = true_long - 0.00569d0 lamda2 = lamda - 0.00479d0*sin(omega/radeg) diff = (lamda - k)/radeg x = atan(-cos(lamda2/radeg)*tan(ob1/radeg))*radeg y = atan(-cos(diff)*tan(i/radeg))*radeg ;---------------------------------------------------; ; Position of north pole (deg) ; ;---------------------------------------------------; pa = x + y ;---------------------------------------------------; ; Latitude at center of disk (deg) ; ;---------------------------------------------------; lat0 = asin(sin(diff)*sin(i/radeg))*radeg ;---------------------------------------------------; ; Longitude at center of disk (deg) ; ;---------------------------------------------------; y = -sin(diff)*cos(i/radeg) x = -cos(diff) recpol, x, y, r, eta, /deg long0 = (eta - theta) mod 360d0 if long0 lt 0 then long0 = long0 + 360d0 ;---------------------------------------------------; ; List values ; ;---------------------------------------------------; if not keyword_set(list) then return print,' ' print,' Sun for '+strtrim(d,2)+' '+(monthnames())(m)+$ ' '+strtrim(yr,2)+' at ET '+strsec(et*3600d0) print,' ' print,' Distance (AU) = '+strtrim(dist,2) print,' Semidiameter (arc sec) = '+strtrim(sd,2) print,' True (long, lat) in degrees = ('+$ strtrim(true_long,2)+', '+strtrim(true_lat,2)+')' print,' Apparent (long, lat) in degrees = ('+$ strtrim(app_long,2)+', '+strtrim(app_lat,2)+')' print,' True (RA, Dec) in hrs, deg = ('+$ strtrim(true_ra,2)+', '+strtrim(true_dec,2)+')' print,' Apparent (RA, Dec) in hrs, deg = ('+$ strtrim(app_ra,2)+', '+strtrim(app_dec,2)+')' print,' Heliographic long. and lat. of disk center in deg = ('+$ strtrim(long0,2)+', '+strtrim(lat0,2)+')' print,' Position angle of north pole in deg = '+$ strtrim(pa,2) print,' The Carrington Rotation Number = '+$ strtrim(carr,2) print,' ' return end