# [AstroPy] Heliocentric Velocity Correction

David Berry d.berry at jach.hawaii.edu
Mon Jun 11 04:24:52 EDT 2012

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 at 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 at 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 at gmail.com>
>> wrote:
>>>
>>> Dear pythoners:
>>>           Is there any python nodule that can make heliocentric velocity
>>> correction well?
>>>           Thank you!
>>
>>
>
>
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