[vsnet-chat 4616] Astrometry from different sources [was:Re: V589 Her]

[Gianluca Masi <gianmasi@fr.flashnet.it>]

Dear Arne,
I was wondering if it was just a coincidence to have my position closer
to the USNO-A possible counterpart, considering that I worked inside the
USNO A2.0 frame of reference. In other words, how important, in
comparing something , is the possibility to work inside the same
framework? 

Thank you in advance for any comment: it is wonderful to have so much
occasions to learn.

Sincerely,
Gianluca



aah@nofs.navy.mil wrote:
> 
> Gianluca posted his astrometry from his images of
> the outburst; Yamaoka-san posted his astrometry from
> the same images.  They differ slightly, due to the
> different reference catalogs and reduction procedures,
> but both are within their errors (I assume anyway;
> Yamaoka did not give any errors for his reductions;
> I would not believe the extra digit of precision until
> I saw formal errors). I don't think there is any relevance
> to Gianluca's measurement being closer to the blue USNO-A star's
> reported position.
>   Note that both of these positions match within
> error to the one shown in Bruce Sumner's sequence
> (from my .dat file; USNO-A2.0, 0.1arcsec internal
> precision, posted May 9):
> http://ftp.nofs.navy.mil/pub/outgoing/aah/sequence/sumner/v589her.seq
> 16 22 07.15  +19 22 37.2   Gianluca
> 16:22:07.164 +19:22:36.91  Yamaoka
> 16 22 07.17  +19 22 37.1   Henden
> 16 22 07.15  +19 22 37.4   USNO-A blue star
> It is nice to see agreement!  This is obviously not a high
> proper motion star.  Since Yamaoka-san notes a fainter companion,
> you should be careful on your photometry as the CV fades.
>   I've copied this to -chat as continued discussion of
> the position is probably not relevant to -alert.
> Arne

-- 
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* Gianluca Masi                           "Two things fill the soul   *
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* web:  http://vsnet.eurolink.it/comets/                  I. Kant       *
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