[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

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

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

Hi Alain,

thank you very much for your help. Works very well.

Kind regards

Klaus

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

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