# [Celestlab] Using celestlab for computing sunrise / sunset and postition of the sun and the moon in the local horizontal system

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## [Celestlab] Using celestlab for computing sunrise / sunset and postition of the sun and the moon in the local horizontal system

 Hi all, I’m new to celestlab. I have the following question: Are their examples available how to calculate sunrise / sunset and position of the sun and the moon in the local horizontal system using celestlab? Thanks in advance. Kind regards Klaus Dipl.-Phys. Klaus RoheAdolf-Kolping-Strasse 10a85625 GlonnE-Mail: [hidden email]Tel.:      +49 (0) 8093 5402Mobil:  +49 (0) 170 8133634  _______________________________________________ Celestlab mailing list [hidden email] http://lists.scilab.org/mailman/listinfo/celestlab
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## Re: [Celestlab] Using celestlab for computing sunrise / sunset and postition of the sun and the moon in the local horizontal system

 Hi,   1)      For the Sun /Moon direction / horizontal plane with CelestLab : yes -          Compute the body position (CL_eph_sun() for instance) -          Convert to the local frame (using CL_gm_stationPointing is probably the simplest way. NB: You need to convert the coordinates from the “inertial” frame (ECI) to the terrestrial frame (ECF).   It would be something like this (look at help pages for more details): cjd0 = CL_dat_cal2cjd(2014, 06, 03); // initial day cjd = cjd0 + (0 : 1/1440 : 1);    sun_eci = CL_eph_sun(cjd); // Earth->Sun in cartesian coordinates sun_ecf = CL_fr_convert("ECI", "ECF", cjd, sun_eci);   location = [0 * %pi/180; 45 * %pi/180; 0];  // geodetic coordinates [azim,elev,dist] = CL_gm_stationPointing(location, sun_ecf);   scf(); plot(cjd-cjd0, elev * 180/%pi);     2)      Sunrise / Sunset : it is not directly computed But you can rather easily  determine the zeros of the Sun elevation. One (approximate) solution is something like : I = Find(elev(1:\$-2) .* elev(2:\$) <= 0) Estimate the zeros by linear interpolation between elev(I) and elev(I+1) [elev has to be computed with a small enough step so that the linear interpolation yields good enough results]   Note: atmospheric corrections are not defined in CelestLab.   Alain     De : Celestlab [mailto:[hidden email]] De la part de Klaus Rohe Envoyé : lundi 2 juin 2014 22:40 À : [hidden email] Objet : [Celestlab] Using celestlab for computing sunrise / sunset and postition of the sun and the moon in the local horizontal system   Hi all,   I’m new to celestlab. I have the following question:   Are their examples available how to calculate sunrise / sunset and position of the sun and the moon in the local horizontal system using celestlab?   Thanks in advance.   Kind regards   Klaus   Dipl.-Phys. Klaus Rohe Adolf-Kolping-Strasse 10a 85625 Glonn E-Mail: [hidden email] Tel.:      +49 (0) 8093 5402 Mobil:  +49 (0) 170 8133634     _______________________________________________ Celestlab mailing list [hidden email] http://lists.scilab.org/mailman/listinfo/celestlab
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## Re: [Celestlab] Using celestlab for computing sunrise / sunset and postition of the sun and the moon in the local horizontal system

 Hi Alain, thank you very much for your help. Works very well. Kind regards Klaus Von: Celestlab [mailto:[hidden email]] Im Auftrag von Lamy AlainGesendet: Mittwoch, 4. Juni 2014 09:29An: The Scilab/CNES moduleBetreff: Re: [Celestlab] Using celestlab for computing sunrise / sunset and postition of the sun and the moon in the local horizontal system Hi,  1)      For the Sun /Moon direction / horizontal plane with CelestLab : yes -          Compute the body position (CL_eph_sun() for instance)-          Convert to the local frame (using CL_gm_stationPointing is probably the simplest way.NB: You need to convert the coordinates from the “inertial” frame (ECI) to the terrestrial frame (ECF).  It would be something like this (look at help pages for more details): cjd0 = CL_dat_cal2cjd(2014, 06, 03); // initial daycjd = cjd0 + (0 : 1/1440 : 1);   sun_eci = CL_eph_sun(cjd); // Earth->Sun in cartesian coordinatessun_ecf = CL_fr_convert("ECI", "ECF", cjd, sun_eci); location = [0 * %pi/180; 45 * %pi/180; 0];  // geodetic coordinates[azim,elev,dist] = CL_gm_stationPointing(location, sun_ecf); scf(); plot(cjd-cjd0, elev * 180/%pi);   2)      Sunrise / Sunset : it is not directly computed But you can rather easily  determine the zeros of the Sun elevation. One (approximate) solution is something like : I = Find(elev(1:\$-2) .* elev(2:\$) <= 0)Estimate the zeros by linear interpolation between elev(I) and elev(I+1)[elev has to be computed with a small enough step so that the linear interpolation yields good enough results] Note: atmospheric corrections are not defined in CelestLab.  Alain  De : Celestlab [[hidden email]] De la part de Klaus RoheEnvoyé : lundi 2 juin 2014 22:40À : [hidden email]Objet : [Celestlab] Using celestlab for computing sunrise / sunset and postition of the sun and the moon in the local horizontal system Hi all, I’m new to celestlab. I have the following question: Are their examples available how to calculate sunrise / sunset and position of the sun and the moon in the local horizontal system using celestlab? Thanks in advance. Kind regards Klaus Dipl.-Phys. Klaus RoheAdolf-Kolping-Strasse 10a85625 GlonnE-Mail: [hidden email]Tel.:      +49 (0) 8093 5402Mobil:  +49 (0) 170 8133634  _______________________________________________ Celestlab mailing list [hidden email] http://lists.scilab.org/mailman/listinfo/celestlab