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

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Klaus Rohe Klaus Rohe
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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 Rohe

Adolf-Kolping-Strasse 10a

85625 Glonn

E-Mail: [hidden email]

Tel.:      +49 (0) 8093 5402

Mobil:  +49 (0) 170 8133634

 

 


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Alain LAMY Alain LAMY
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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

 

 


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Klaus Rohe Klaus Rohe
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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 Alain
Gesend
et: Mittwoch, 4. Juni 2014 09:29
An: The Scilab/CNES module
Betreff: 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 [[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

 

 


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