[AstroPy] Heliocentric Velocity Correction

gonghang.naoc ghang.naoc@gmail....
Mon Jun 11 04:36:19 CDT 2012


   Thank you.

> I just want to get  the radial velocity  a star  in heliocentric
> coordinate.I think the the heliocentric correction depends on the position
> of the observatory,but the input parameters of astrolib.baryvel  are just
> dje and deq.The result is a 3d velocity.My question is  whether the
> velocity is the velocity of the  center of the earth and if not,whether I
> can input the observatory parameters,i.e. longitude,latitude,elevation.
>
>
> On Mon, Jun 11, 2012 at 4:24 PM, David Berry <d.berry@jach.hawaii.edu>wrote:
>
>> Sorry - I'm not sure I understand your question. I thought you were
>> trying to convert spectral positions (frequencies, velocities,
>> wavelengths, etc) into the heliocentric rest frame from some other
>> rest frame.
>>
>> The exact set of properties you need to specify when converting
>> spectral positions depends on your original rest frame. I used
>> topocentric as an example, and so included the observatory position.
>> If instead I had used (for instance) geocentric, then the observatory
>> position would not have been needed.
>>
>> But I see that astrolib.baryvel just returns the velocity of the earth
>> in the barycentric or heliocentric rest frame, so now I'm not sure
>> what it is you are trying to do. What velocity is it you are trying to
>> correct?
>>
>> David
>>
>> On 11 June 2012 08:58, gonghang.naoc <ghang.naoc@gmail.com> wrote:
>> > Hi,according to the link below,the 3d velocity we get from astrolib has
>> > nothing to do with the observatory position.My question is  the 3d
>> velocity
>> > is just the velocity of earth center?As the author claimed the precision
>> > level is cm/s, is it necessary to  input the  longtitude, latitude and
>> > elevation of the observatory?
>> >
>> > Thank you!
>> >
>> >
>> > http://www.astro.ucla.edu/~ianc/python/astrolib.htmlIDL> baryvel, jd,
>> 2000,
>> > vh, vb, /jpl ;JPL ephemeris ==> vh = [-17.07236, -22.81126, -9.889419]
>> > ;Heliocentric km/s ==> vb = [-17.08083, -22.80484, -9.886409]
>> ;Barycentric
>> > km/s
>> >
>> >
>> >
>> >
>> > On Sat, Jun 9, 2012 at 4:20 PM, gonghang.naoc <ghang.naoc@gmail.com>
>> wrote:
>> >>
>> >> I have checked
>> >> http://code.google.com/p/astrolibpy/source/browse/#git%2Fastrolib  and
>> >> http://www.astro.ucla.edu/~ianc/python/astrolib.html
>> >> Is there a whole astrolib module I can download and install? Or is
>> there
>> >> any other python module that can makes heliocentric velocity
>> correction you
>> >> suggest?
>> >> Thank you very much!
>> >>
>> >>
>> >> On Sat, Jun 9, 2012 at 10:52 AM, gonghang.naoc <ghang.naoc@gmail.com>
>> >> wrote:
>> >>>
>> >>> Dear pythoners:
>> >>>           Is there any python nodule that can make heliocentric
>> velocity
>> >>> correction well?
>> >>>           Thank you!
>> >>
>> >>
>> >
>> >
>> > _______________________________________________
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>> > AstroPy@scipy.org
>> > http://mail.scipy.org/mailman/listinfo/astropy
>> >
>>
>
>
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