## Re: [SWISSEPH] how to calculate the moon parallax

Expand Messages
• ... Clement, you can use the function swe_pheno() or swe_pheno_ut(). The function returns: * attr[0] = phase angle (earth-planet-sun) * attr[1] = phase
Message 1 of 11 , Oct 23, 2008
> Does anyone know whether there is a way directly or indirectly with Swiss ephemeris to calculate the moon parallax for any given time and location?

Clement,

you can use the function swe_pheno() or swe_pheno_ut().

The function returns:
* attr[0] = phase angle (earth-planet-sun)
* attr[1] = phase (illumined fraction of disc)
* attr[2] = elongation of planet
* attr[3] = apparent diameter of disc
* attr[4] = apparent magnitude
* attr[5] = geocentric horizontal parallax (Moon)
* declare as attr[20] at least !

But you need the newest Swiss Ephemeris version 1.75 if you need
topocentric values.

I fixed this only recently but forgot to mention it in the release history.

Regards

Dieter

>
> thanks.
>
> Clement
>
> [Non-text portions of this message have been removed]
>
>
> ------------------------------------
>
>
>
>
• Dear Dieter, According my understanding Moon Parallax Correction is related to position (Lat and Lon) I understand Moon parallax correction is Maximum (close
Message 2 of 11 , Oct 23, 2008
Dear Dieter,

According my understanding Moon Parallax Correction is related to position (Lat and Lon)

I understand Moon parallax correction is Maximum (close to 57 mins) in ASC ,  null when located in MC and IC and Minus 57 mins in DSC.

I can not see position parameters in SWE_Pheno function.

Regards

________________________________
From: Dieter Koch <dieter@...>
To: swisseph@yahoogroups.com
Sent: Thursday, October 23, 2008 8:19:47 AM
Subject: Re: [SWISSEPH] how to calculate the moon parallax

> Does anyone know whether there is a way directly or indirectly with Swiss ephemeris to calculate the moon parallax for any given time and location?

Clement,

you can use the function swe_pheno() or swe_pheno_ut( ).

The function returns:
* attr[0] = phase angle (earth-planet- sun)
* attr[1] = phase (illumined fraction of disc)
* attr[2] = elongation of planet
* attr[3] = apparent diameter of disc
* attr[4] = apparent magnitude
* attr[5] = geocentric horizontal parallax (Moon)
* declare as attr[20] at least !

But you need the newest Swiss Ephemeris version 1.75 if you need
topocentric values.

I fixed this only recently but forgot to mention it in the release history.

Regards

Dieter

>
> thanks.
>
> Clement
>
> [Non-text portions of this message have been removed]
>
>
> ------------ --------- --------- ------
>
>
>
>

[Non-text portions of this message have been removed]
• ... To set the geographic position, use the function swe_set_topo(long, lat, altitude). After that call swe_pheno_ut() for the moon with iflag |= SE_TOPOCTR
Message 3 of 11 , Oct 23, 2008
> Dear Dieter,
>
> According my understanding Moon Parallax Correction is related to position (Lat and Lon)
>
> I understand Moon parallax correction is Maximum (close to 57 mins) in ASC ,  null when located in MC and IC and Minus 57 mins in DSC.
>
> I can not see position parameters in SWE_Pheno function.

To set the geographic position, use the function
swe_set_topo(long, lat, altitude).

After that call swe_pheno_ut() for the moon with iflag |= SE_TOPOCTR for
topocentric calculation of all output values including horizontal
parallax.

Regards

Dieter

>
>
>
> Regards
>
>
>
>
> ________________________________
> From: Dieter Koch <dieter@...>
> To: swisseph@yahoogroups.com
> Sent: Thursday, October 23, 2008 8:19:47 AM
> Subject: Re: [SWISSEPH] how to calculate the moon parallax
>
>
>> Does anyone know whether there is a way directly or indirectly with Swiss ephemeris to calculate the moon parallax for any given time and location?
>
> Clement,
>
> you can use the function swe_pheno() or swe_pheno_ut( ).
>
> The function returns:
> * attr[0] = phase angle (earth-planet- sun)
> * attr[1] = phase (illumined fraction of disc)
> * attr[2] = elongation of planet
> * attr[3] = apparent diameter of disc
> * attr[4] = apparent magnitude
> * attr[5] = geocentric horizontal parallax (Moon)
> * declare as attr[20] at least !
>
> But you need the newest Swiss Ephemeris version 1.75 if you need
> topocentric values.
>
> I fixed this only recently but forgot to mention it in the release history.
>
> Regards
>
> Dieter
>
>>
>> thanks.
>>
>> Clement
>>
>> [Non-text portions of this message have been removed]
>>
>>
>> ------------ --------- --------- ------
>>
>>
>>
>>
>
>
>
>
>
> [Non-text portions of this message have been removed]
>
>
> ------------------------------------
>
>
>
>
>

[Non-text portions of this message have been removed]
• Thank You Dieter for your promp response. I followed your instructions and now Attr (5) is sensible to Position  but is not sensible to Time during the day
Message 4 of 11 , Oct 23, 2008
Thank You Dieter for your promp response.

I followed your instructions and now Attr (5) is sensible to Position  but is not sensible to Time during the day ... i.e Moon parallax correction is the same if Time is 9 AM or 9 PM.

My understanding is :
If a Chart has the Moon in ASC at 9 AM, Moon Parallax Correction is close to +1 Deg at 9 PM is close to DSC and Moon parallax Correction is close to -1 Deg

Regards

Juan

________________________________
From: Dieter Koch <dieter@...>
To: swisseph@yahoogroups.com
Sent: Thursday, October 23, 2008 11:55:14 AM
Subject: Re: [SWISSEPH] how to calculate the moon parallax

> Dear Dieter,
>
> According my understanding Moon Parallax Correction is related to position (Lat and Lon)
>
> I understand Moon parallax correction is Maximum (close to 57 mins) in ASC ,  null when located in MC and IC and Minus 57 mins in DSC.
>
> I can not see position parameters in SWE_Pheno function.

To set the geographic position, use the function
swe_set_topo( long, lat, altitude).

After that call swe_pheno_ut( ) for the moon with iflag |= SE_TOPOCTR for
topocentric calculation of all output values including horizontal
parallax.

Regards

Dieter

>
>
>
> Regards
>
>
>
>
> ____________ _________ _________ __
> From: Dieter Koch <dieter@astro. ch>
> To: swisseph@yahoogroup s.com
> Sent: Thursday, October 23, 2008 8:19:47 AM
> Subject: Re: [SWISSEPH] how to calculate the moon parallax
>
>
>> Does anyone know whether there is a way directly or indirectly with Swiss ephemeris to calculate the moon parallax for any given time and location?
>
> Clement,
>
> you can use the function swe_pheno() or swe_pheno_ut( ).
>
> The function returns:
> * attr[0] = phase angle (earth-planet- sun)
> * attr[1] = phase (illumined fraction of disc)
> * attr[2] = elongation of planet
> * attr[3] = apparent diameter of disc
> * attr[4] = apparent magnitude
> * attr[5] = geocentric horizontal parallax (Moon)
> * declare as attr[20] at least !
>
> But you need the newest Swiss Ephemeris version 1.75 if you need
> topocentric values.
>
> I fixed this only recently but forgot to mention it in the release history.
>
> Regards
>
> Dieter
>
>>
>> thanks.
>>
>> Clement
>>
>> [Non-text portions of this message have been removed]
>>
>>
>> ------------ --------- --------- ------
>>
>>
>>
>>
>
>
>
>
>
> [Non-text portions of this message have been removed]
>
>
> ------------ --------- --------- ------
>
>
>
>
>

[Non-text portions of this message have been removed]

[Non-text portions of this message have been removed]
• Hi Dieter, Is this the same parallax(in degrees) is the one that may be use to gauge the distance of the moon from earth? .eg the parallax is smaller when the
Message 5 of 11 , Oct 23, 2008
Hi Dieter,

Is this the same parallax(in degrees) is the one that may be use to gauge the distance of the moon from earth? .eg the parallax is smaller when the moon is further away from earth and largest when it's closest to the earth.

thanks.

Clement

----- Original Message -----
From: Dieter Koch
To: swisseph@yahoogroups.com
Sent: Thursday, October 23, 2008 9:19 PM
Subject: Re: [SWISSEPH] how to calculate the moon parallax

> Does anyone know whether there is a way directly or indirectly with Swiss ephemeris to calculate the moon parallax for any given time and location?

Clement,

you can use the function swe_pheno() or swe_pheno_ut().

The function returns:
* attr[0] = phase angle (earth-planet-sun)
* attr[1] = phase (illumined fraction of disc)
* attr[2] = elongation of planet
* attr[3] = apparent diameter of disc
* attr[4] = apparent magnitude
* attr[5] = geocentric horizontal parallax (Moon)
* declare as attr[20] at least !

But you need the newest Swiss Ephemeris version 1.75 if you need
topocentric values.

I fixed this only recently but forgot to mention it in the release history.

Regards

Dieter

>
> thanks.
>
> Clement
>
> [Non-text portions of this message have been removed]
>
>
> ------------------------------------
>
>
>
>

[Non-text portions of this message have been removed]
• ... Juan, I don t understand exactly your question, but parallax has no sign (+/-). The horizontal parallax of the Moon it is just the difference between its
Message 6 of 11 , Oct 24, 2008
On Thu, 23 Oct 2008, Juan Bachisio wrote:

> Thank You Dieter for your promp response.
>
> I followed your instructions and now Attr (5) is sensible to Position  but is not sensible to Time during the day ... i.e Moon parallax correction is the same if Time is 9 AM or 9 PM.
>
> My understanding is :
> If a Chart has the Moon in ASC at 9 AM, Moon Parallax Correction is close to +1 Deg at 9 PM is close to DSC and Moon parallax Correction is close to -1 Deg

Juan,

I don't understand exactly your question, but parallax has no sign (+/-).
The horizontal parallax of the Moon it is just the difference between its
topocentric and the geocentric position when it is on the astronomical
horizon.

Regards

Dieter

>
>
> Regards
>
> Juan
>
>
>
>
> ________________________________
> From: Dieter Koch <dieter@...>
> To: swisseph@yahoogroups.com
> Sent: Thursday, October 23, 2008 11:55:14 AM
> Subject: Re: [SWISSEPH] how to calculate the moon parallax
>
>
>> Dear Dieter,
>>
>> According my understanding Moon Parallax Correction is related to position (Lat and Lon)
>>
>> I understand Moon parallax correction is Maximum (close to 57 mins) in ASC ,  null when located in MC and IC and Minus 57 mins in DSC.
>>
>> I can not see position parameters in SWE_Pheno function.
>
> To set the geographic position, use the function
> swe_set_topo( long, lat, altitude).
>
> After that call swe_pheno_ut( ) for the moon with iflag |= SE_TOPOCTR for
> topocentric calculation of all output values including horizontal
> parallax.
>
> Regards
>
> Dieter
>
>>
>>
>>
>> Regards
>>
>>
>>
>>
>> ____________ _________ _________ __
>> From: Dieter Koch <dieter@astro. ch>
>> To: swisseph@yahoogroup s.com
>> Sent: Thursday, October 23, 2008 8:19:47 AM
>> Subject: Re: [SWISSEPH] how to calculate the moon parallax
>>
>>
>>> Does anyone know whether there is a way directly or indirectly with Swiss ephemeris to calculate the moon parallax for any given time and location?
>>
>> Clement,
>>
>> you can use the function swe_pheno() or swe_pheno_ut( ).
>>
>> The function returns:
>> * attr[0] = phase angle (earth-planet- sun)
>> * attr[1] = phase (illumined fraction of disc)
>> * attr[2] = elongation of planet
>> * attr[3] = apparent diameter of disc
>> * attr[4] = apparent magnitude
>> * attr[5] = geocentric horizontal parallax (Moon)
>> * declare as attr[20] at least !
>>
>> But you need the newest Swiss Ephemeris version 1.75 if you need
>> topocentric values.
>>
>> I fixed this only recently but forgot to mention it in the release history.
>>
>> Regards
>>
>> Dieter
>>
>>>
>>> thanks.
>>>
>>> Clement
>>>
>>> [Non-text portions of this message have been removed]
>>>
>>>
>>> ------------ --------- --------- ------
>>>
>>>
>>>
>>>
>>
>>
>>
>>
>>
>> [Non-text portions of this message have been removed]
>>
>>
>> ------------ --------- --------- ------
>>
>>
>>
>>
>>
>
> [Non-text portions of this message have been removed]
>
>
>
>
>
>
> [Non-text portions of this message have been removed]
>
>
> ------------------------------------
>
>
>
>
>

[Non-text portions of this message have been removed]
• ... Clement, the answer is here: http://en.wikipedia.org/wiki/Parallax#Lunar_parallax Regards Dieter
Message 7 of 11 , Oct 24, 2008
> Hi Dieter,
>
> Is this the same parallax(in degrees) is the one that may be use to gauge the distance of the moon from earth? .eg the parallax is smaller when the moon is further away from earth and largest when it's closest to the earth.

Clement,

http://en.wikipedia.org/wiki/Parallax#Lunar_parallax

Regards

Dieter

>
> thanks.
>
> Clement
>
> ----- Original Message -----
> From: Dieter Koch
> To: swisseph@yahoogroups.com
> Sent: Thursday, October 23, 2008 9:19 PM
> Subject: Re: [SWISSEPH] how to calculate the moon parallax
>
>
> > Does anyone know whether there is a way directly or indirectly with Swiss ephemeris to calculate the moon parallax for any given time and location?
>
> Clement,
>
> you can use the function swe_pheno() or swe_pheno_ut().
>
> The function returns:
> * attr[0] = phase angle (earth-planet-sun)
> * attr[1] = phase (illumined fraction of disc)
> * attr[2] = elongation of planet
> * attr[3] = apparent diameter of disc
> * attr[4] = apparent magnitude
> * attr[5] = geocentric horizontal parallax (Moon)
> * declare as attr[20] at least !
>
> But you need the newest Swiss Ephemeris version 1.75 if you need
> topocentric values.
>
> I fixed this only recently but forgot to mention it in the release history.
>
> Regards
>
> Dieter
>
> >
> > thanks.
> >
> > Clement
> >
> > [Non-text portions of this message have been removed]
> >
> >
> > ------------------------------------
> >
> >
> >
> >
>
>
>
>
> [Non-text portions of this message have been removed]
>
>
> ------------------------------------
>
>
>
>
• Dear Dieter, Please take a look to this site http://mysite.verizon.net/bonniehill/pages.aux/astrology/parallax/lunar.parallax.html Mayor programs include Moon
Message 8 of 11 , Oct 24, 2008
Dear Dieter,

Please take a look to this site

http://mysite.verizon.net/bonniehill/pages.aux/astrology/parallax/lunar.parallax.html

Mayor programs include Moon Parallax correction working acording to this, in particular those oriented to Vedic astrology.

Regards

Juan

________________________________
From: Dieter Koch <dieter@...>
To: swisseph@yahoogroups.com
Sent: Friday, October 24, 2008 4:08:54 AM
Subject: Re: [SWISSEPH] how to calculate the moon parallax

On Thu, 23 Oct 2008, Juan Bachisio wrote:

> Thank You Dieter for your promp response.
>
> I followed your instructions and now Attr (5) is sensible to Position  but is not sensible to Time during the day ... i.e Moon parallax correction is the same if Time is 9 AM or 9 PM.
>
> My understanding is :
> If a Chart has the Moon in ASC at 9 AM, Moon Parallax Correction is close to +1 Deg at 9 PM is close to DSC and Moon parallax Correction is close to -1 Deg

Juan,

I don't understand exactly your question, but parallax has no sign (+/-).
The horizontal parallax of the Moon it is just the difference between its
topocentric and the geocentric position when it is on the astronomical
horizon.

Regards

Dieter

>
>
> Regards
>
> Juan
>
>
>
>
> ____________ _________ _________ __
> From: Dieter Koch <dieter@astro. ch>
> To: swisseph@yahoogroup s.com
> Sent: Thursday, October 23, 2008 11:55:14 AM
> Subject: Re: [SWISSEPH] how to calculate the moon parallax
>
>
>> Dear Dieter,
>>
>> According my understanding Moon Parallax Correction is related to position (Lat and Lon)
>>
>> I understand Moon parallax correction is Maximum (close to 57 mins) in ASC ,  null when located in MC and IC and Minus 57 mins in DSC.
>>
>> I can not see position parameters in SWE_Pheno function.
>
> To set the geographic position, use the function
> swe_set_topo( long, lat, altitude).
>
> After that call swe_pheno_ut( ) for the moon with iflag |= SE_TOPOCTR for
> topocentric calculation of all output values including horizontal
> parallax.
>
> Regards
>
> Dieter
>
>>
>>
>>
>> Regards
>>
>>
>>
>>
>> ____________ _________ _________ __
>> From: Dieter Koch <dieter@astro. ch>
>> To: swisseph@yahoogroup s.com
>> Sent: Thursday, October 23, 2008 8:19:47 AM
>> Subject: Re: [SWISSEPH] how to calculate the moon parallax
>>
>>
>>> Does anyone know whether there is a way directly or indirectly with Swiss ephemeris to calculate the moon parallax for any given time and location?
>>
>> Clement,
>>
>> you can use the function swe_pheno() or swe_pheno_ut( ).
>>
>> The function returns:
>> * attr[0] = phase angle (earth-planet- sun)
>> * attr[1] = phase (illumined fraction of disc)
>> * attr[2] = elongation of planet
>> * attr[3] = apparent diameter of disc
>> * attr[4] = apparent magnitude
>> * attr[5] = geocentric horizontal parallax (Moon)
>> * declare as attr[20] at least !
>>
>> But you need the newest Swiss Ephemeris version 1.75 if you need
>> topocentric values.
>>
>> I fixed this only recently but forgot to mention it in the release history.
>>
>> Regards
>>
>> Dieter
>>
>>>
>>> thanks.
>>>
>>> Clement
>>>
>>> [Non-text portions of this message have been removed]
>>>
>>>
>>> ------------ --------- --------- ------
>>>
>>>
>>>
>>>
>>
>>
>>
>>
>>
>> [Non-text portions of this message have been removed]
>>
>>
>> ------------ --------- --------- ------
>>
>>
>>
>>
>>
>
> [Non-text portions of this message have been removed]
>
>
>
>
>
>
> [Non-text portions of this message have been removed]
>
>
> ------------ --------- --------- ------
>
>
>
>
>

[Non-text portions of this message have been removed]

[Non-text portions of this message have been removed]
• ... If you want topocentric (= parallax-corrected ) lunar positions, you can have this much easier: swe_set_topo(long, lat, altitude); swe_calc_ut(tjd,
Message 9 of 11 , Oct 24, 2008
On Fri, 24 Oct 2008, Juan Bachisio wrote:

> Dear Dieter,
>
> Please take a look to this site
>
> http://mysite.verizon.net/bonniehill/pages.aux/astrology/parallax/lunar.parallax.html
>
> Mayor programs include Moon Parallax correction working acording to this, in particular those oriented to Vedic astrology.

If you want topocentric (= "parallax-corrected") lunar positions, you can
have this much easier:

swe_set_topo(long, lat, altitude);
swe_calc_ut(tjd, SE_MOON, SEFLG_TOPOCTR, ...);

This is also implemented in swetest.

The example of the page you mention is:

> For our test, we will use April 30, 2005 at 10:00 am EST in New York City (74:00:00 W, 40:43:00 N). We will calculate the longitude of the Moon.
>
> Type of Calculation Astrolog Lunar Par Calc
> Tropical, Non-parallax: 1 Aqu 50 45 1 Aqu 50 12
> Tropical, Parallax: N/A 1 Aqu 00 28

We can reproduce that with swetest as follows:
swetest -b30.4.2005 -p1 -fPZ -ut15 -head
Moon 1 aq 50'45.5815 tropical geocentric
swetest -b30.4.2005 -p1 -fPZ -ut15 -topo-74.0,40.716667,0 -head
Moon 1 aq 1' 2.0825 tropical topocentric

If you subtract the difference between Astrolog and Lunar Par Calc (33 arc sec)
you get the same result as Lunar Par Calc.

Regards

Dieter

>
> Regards
>
> Juan
>
>
>
>
> ________________________________
> From: Dieter Koch <dieter@...>
> To: swisseph@yahoogroups.com
> Sent: Friday, October 24, 2008 4:08:54 AM
> Subject: Re: [SWISSEPH] how to calculate the moon parallax
>
>
> On Thu, 23 Oct 2008, Juan Bachisio wrote:
>
>> Thank You Dieter for your promp response.
>>
>> I followed your instructions and now Attr (5) is sensible to Position  but is not sensible to Time during the day ... i.e Moon parallax correction is the same if Time is 9 AM or 9 PM.
>>
>> My understanding is :
>> If a Chart has the Moon in ASC at 9 AM, Moon Parallax Correction is close to +1 Deg at 9 PM is close to DSC and Moon parallax Correction is close to -1 Deg
>
> Juan,
>
> I don't understand exactly your question, but parallax has no sign (+/-).
> The horizontal parallax of the Moon it is just the difference between its
> topocentric and the geocentric position when it is on the astronomical
> horizon.
>
> Regards
>
> Dieter
>
>>
>>
>> Regards
>>
>> Juan
>>
>>
>>
>>
>> ____________ _________ _________ __
>> From: Dieter Koch <dieter@astro. ch>
>> To: swisseph@yahoogroup s.com
>> Sent: Thursday, October 23, 2008 11:55:14 AM
>> Subject: Re: [SWISSEPH] how to calculate the moon parallax
>>
>>
>>> Dear Dieter,
>>>
>>> According my understanding Moon Parallax Correction is related to position (Lat and Lon)
>>>
>>> I understand Moon parallax correction is Maximum (close to 57 mins) in ASC ,  null when located in MC and IC and Minus 57 mins in DSC.
>>>
>>> I can not see position parameters in SWE_Pheno function.
>>
>> To set the geographic position, use the function
>> swe_set_topo( long, lat, altitude).
>>
>> After that call swe_pheno_ut( ) for the moon with iflag |= SE_TOPOCTR for
>> topocentric calculation of all output values including horizontal
>> parallax.
>>
>> Regards
>>
>> Dieter
>>
>>>
>>>
>>>
>>> Regards
>>>
>>>
>>>
>>>
>>> ____________ _________ _________ __
>>> From: Dieter Koch <dieter@astro. ch>
>>> To: swisseph@yahoogroup s.com
>>> Sent: Thursday, October 23, 2008 8:19:47 AM
>>> Subject: Re: [SWISSEPH] how to calculate the moon parallax
>>>
>>>
>>>> Does anyone know whether there is a way directly or indirectly with Swiss ephemeris to calculate the moon parallax for any given time and location?
>>>
>>> Clement,
>>>
>>> you can use the function swe_pheno() or swe_pheno_ut( ).
>>>
>>> The function returns:
>>> * attr[0] = phase angle (earth-planet- sun)
>>> * attr[1] = phase (illumined fraction of disc)
>>> * attr[2] = elongation of planet
>>> * attr[3] = apparent diameter of disc
>>> * attr[4] = apparent magnitude
>>> * attr[5] = geocentric horizontal parallax (Moon)
>>> * declare as attr[20] at least !
>>>
>>> But you need the newest Swiss Ephemeris version 1.75 if you need
>>> topocentric values.
>>>
>>> I fixed this only recently but forgot to mention it in the release history.
>>>
>>> Regards
>>>
>>> Dieter
>>>
>>>>
>>>> thanks.
>>>>
>>>> Clement
>>>>
>>>> [Non-text portions of this message have been removed]
>>>>
>>>>
>>>> ------------ --------- --------- ------
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>>
>>>
>>>
>>> [Non-text portions of this message have been removed]
>>>
>>>
>>> ------------ --------- --------- ------
>>>
>>>
>>>
>>>
>>>
>>
>> [Non-text portions of this message have been removed]
>>
>>
>>
>>
>>
>>
>> [Non-text portions of this message have been removed]
>>
>>
>> ------------ --------- --------- ------
>>
>>
>>
>>
>>
>
> [Non-text portions of this message have been removed]
>
>
>
>
>
>
> [Non-text portions of this message have been removed]
>
>
> ------------------------------------
>
>
>
>
>

[Non-text portions of this message have been removed]
• Thank you Very Much Dieter Juan ________________________________ From: Dieter Koch To: swisseph@yahoogroups.com Sent: Friday, October 24,
Message 10 of 11 , Oct 24, 2008
Thank you Very Much Dieter

Juan

________________________________
From: Dieter Koch <dieter@...>
To: swisseph@yahoogroups.com
Sent: Friday, October 24, 2008 9:44:24 AM
Subject: Re: [SWISSEPH] how to calculate the moon parallax

On Fri, 24 Oct 2008, Juan Bachisio wrote:

> Dear Dieter,
>
> Please take a look to this site
>
> http://mysite. verizon.net/ bonniehill/ pages.aux/ astrology/ parallax/ lunar.parallax. html
>
> Mayor programs include Moon Parallax correction working acording to this, in particular those oriented to Vedic astrology.

If you want topocentric (= "parallax-corrected ") lunar positions, you can
have this much easier:

swe_set_topo( long, lat, altitude);
swe_calc_ut( tjd, SE_MOON, SEFLG_TOPOCTR, ...);

This is also implemented in swetest.

The example of the page you mention is:

> For our test, we will use April 30, 2005 at 10:00 am EST in New York City (74:00:00 W, 40:43:00 N). We will calculate the longitude of the Moon.
>
> Type of Calculation Astrolog Lunar Par Calc
> Tropical, Non-parallax: 1 Aqu 50 45 1 Aqu 50 12
> Tropical, Parallax: N/A 1 Aqu 00 28

We can reproduce that with swetest as follows:
swetest -b30.4.2005 -p1 -fPZ -ut15 -head
Moon 1 aq 50'45.5815 tropical geocentric
swetest -b30.4.2005 -p1 -fPZ -ut15 -topo-74.0,40. 716667,0 -head
Moon 1 aq 1' 2.0825 tropical topocentric

If you subtract the difference between Astrolog and Lunar Par Calc (33 arc sec)
you get the same result as Lunar Par Calc.

Regards

Dieter

>
> Regards
>
> Juan
>
>
>
>
> ____________ _________ _________ __
> From: Dieter Koch <dieter@astro. ch>
> To: swisseph@yahoogroup s.com
> Sent: Friday, October 24, 2008 4:08:54 AM
> Subject: Re: [SWISSEPH] how to calculate the moon parallax
>
>
> On Thu, 23 Oct 2008, Juan Bachisio wrote:
>
>> Thank You Dieter for your promp response.
>>
>> I followed your instructions and now Attr (5) is sensible to Position  but is not sensible to Time during the day ... i.e Moon parallax correction is the same if Time is 9 AM or 9 PM.
>>
>> My understanding is :
>> If a Chart has the Moon in ASC at 9 AM, Moon Parallax Correction is close to +1 Deg at 9 PM is close to DSC and Moon parallax Correction is close to -1 Deg
>
> Juan,
>
> I don't understand exactly your question, but parallax has no sign (+/-).
> The horizontal parallax of the Moon it is just the difference between its
> topocentric and the geocentric position when it is on the astronomical
> horizon.
>
> Regards
>
> Dieter
>
>>
>>
>> Regards
>>
>> Juan
>>
>>
>>
>>
>> ____________ _________ _________ __
>> From: Dieter Koch <dieter@astro. ch>
>> To: swisseph@yahoogroup s.com
>> Sent: Thursday, October 23, 2008 11:55:14 AM
>> Subject: Re: [SWISSEPH] how to calculate the moon parallax
>>
>>
>>> Dear Dieter,
>>>
>>> According my understanding Moon Parallax Correction is related to position (Lat and Lon)
>>>
>>> I understand Moon parallax correction is Maximum (close to 57 mins) in ASC ,  null when located in MC and IC and Minus 57 mins in DSC.
>>>
>>> I can not see position parameters in SWE_Pheno function.
>>
>> To set the geographic position, use the function
>> swe_set_topo( long, lat, altitude).
>>
>> After that call swe_pheno_ut( ) for the moon with iflag |= SE_TOPOCTR for
>> topocentric calculation of all output values including horizontal
>> parallax.
>>
>> Regards
>>
>> Dieter
>>
>>>
>>>
>>>
>>> Regards
>>>
>>>
>>>
>>>
>>> ____________ _________ _________ __
>>> From: Dieter Koch <dieter@astro. ch>
>>> To: swisseph@yahoogroup s.com
>>> Sent: Thursday, October 23, 2008 8:19:47 AM
>>> Subject: Re: [SWISSEPH] how to calculate the moon parallax
>>>
>>>
>>>> Does anyone know whether there is a way directly or indirectly with Swiss ephemeris to calculate the moon parallax for any given time and location?
>>>
>>> Clement,
>>>
>>> you can use the function swe_pheno() or swe_pheno_ut( ).
>>>
>>> The function returns:
>>> * attr[0] = phase angle (earth-planet- sun)
>>> * attr[1] = phase (illumined fraction of disc)
>>> * attr[2] = elongation of planet
>>> * attr[3] = apparent diameter of disc
>>> * attr[4] = apparent magnitude
>>> * attr[5] = geocentric horizontal parallax (Moon)
>>> * declare as attr[20] at least !
>>>
>>> But you need the newest Swiss Ephemeris version 1.75 if you need
>>> topocentric values.
>>>
>>> I fixed this only recently but forgot to mention it in the release history.
>>>
>>> Regards
>>>
>>> Dieter
>>>
>>>>
>>>> thanks.
>>>>
>>>> Clement
>>>>
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