OK, I changed the Equinox Epoch to 2015.2.? It is closer, but still not on the money.? Also, I understand that the Earth axis of rotation is processing (axis moving with respect to the galactic frame), but does the axis location on the surface of the Earth also wander significantly?? I am sure it has to at least a little as the center of mass is mobil due to the Earth's interior being molten.? However, I am not certain if this also effects the location of the stars.
Chris
On Sat, Sep 5, 2015 at 5:14 PM, Chris Maness <
chris@...> wrote:
> The Xephem RA/DEC matches the J2000 Astrometric RA/DEC in Cartes du
> Ciel.? So does that mean Cartes du Ciel is extrapolating out the
> geocentric star positions and that is why they match the USNO data?
>
> Thanks,
> Chris Maness
>
> On Sat, Sep 5, 2015 at 3:29 PM, Ernie Wright
erniew@...
> [xephem] <
xephem@...> wrote:
>> On 09/05/2015 11:09 AM, Chris Maness
chris@... [xephem] wrote:
>>
>>> Strangely, xephem disagrees with Cartes du Ciel on Polaris' RA/DEC,
>>> but agree exactly on AZ/EL.? How could this be?
>>
>> First guess would be an epoch mismatch.? RA/Dec changes over time, so
>> you need to be sure that xephem and Cartes du Ciel are telling you the
>> RA/Dec at the same epoch and equinox.
>>
>> - Ernie? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?
>>
>>
>> ------------------------------------
>> Posted by: Ernie Wright <
erniew@...>
>> ------------------------------------
>>
>>
>> ------------------------------------
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