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Re: [SWISSEPH] how to calculate the moon parallax

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  • Dieter Koch
    ... 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 1 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
      >
      >>
      >> Thak you in advance
      >>
      >> 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
      >>
      >>>
      >>> Thank you in advance for your comments
      >>>
      >>>
      >>> 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]
      >>>>
      >>>>
      >>>> ------------ --------- --------- ------
      >>>>
      >>>> Yahoo! Groups Links
      >>>>
      >>>>
      >>>>
      >>>
      >>>
      >>>
      >>>
      >>>
      >>> [Non-text portions of this message have been removed]
      >>>
      >>>
      >>> ------------ --------- --------- ------
      >>>
      >>> Yahoo! Groups Links
      >>>
      >>>
      >>>
      >>>
      >>
      >> [Non-text portions of this message have been removed]
      >>
      >>
      >>
      >>
      >>
      >>
      >> [Non-text portions of this message have been removed]
      >>
      >>
      >> ------------ --------- --------- ------
      >>
      >> Yahoo! Groups Links
      >>
      >>
      >>
      >>
      >
      > [Non-text portions of this message have been removed]
      >
      >
      >
      >
      >
      >
      > [Non-text portions of this message have been removed]
      >
      >
      > ------------------------------------
      >
      > Yahoo! Groups Links
      >
      >
      >
      >

      [Non-text portions of this message have been removed]
    • Juan Bachisio
      Thank you Very Much Dieter Juan ________________________________ From: Dieter Koch To: swisseph@yahoogroups.com Sent: Friday, October 24,
      Message 2 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
        >
        >>
        >> Thak you in advance
        >>
        >> 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
        >>
        >>>
        >>> Thank you in advance for your comments
        >>>
        >>>
        >>> 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]
        >>>>
        >>>>
        >>>> ------------ --------- --------- ------
        >>>>
        >>>> Yahoo! Groups Links
        >>>>
        >>>>
        >>>>
        >>>
        >>>
        >>>
        >>>
        >>>
        >>> [Non-text portions of this message have been removed]
        >>>
        >>>
        >>> ------------ --------- --------- ------
        >>>
        >>> Yahoo! Groups Links
        >>>
        >>>
        >>>
        >>>
        >>
        >> [Non-text portions of this message have been removed]
        >>
        >>
        >>
        >>
        >>
        >>
        >> [Non-text portions of this message have been removed]
        >>
        >>
        >> ------------ --------- --------- ------
        >>
        >> Yahoo! Groups Links
        >>
        >>
        >>
        >>
        >
        > [Non-text portions of this message have been removed]
        >
        >
        >
        >
        >
        >
        > [Non-text portions of this message have been removed]
        >
        >
        > ------------ --------- --------- ------
        >
        > Yahoo! Groups Links
        >
        >
        >
        >

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






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