[vsnet-chat 3448] Re: Astrometry of Novae

[Brian Skiff <bas@lowell.edu>]

     Kato-san wrote:
> The accurate astrometry [of V1974 Cyg]...was later found to be inconsistent 
> with radio interferometric astrometry.

     Yep, that is my "error", although a complicated case.  I used a Pluto
Camera plate taken under difficult circumstances for the discovery 
confirmation, and this in turn to examine the POSS-I prints (all there was
at the time).  This led to a faint star that seemed like a reasonable
candidate.  However, the Carlsberg astrometry and radio interferometry (the
now disassembled MERLIN system in the UK) showed the position to be about 2"
off mostly in Dec.  The true progenitor is visible at mag. 21 on the       
overlapping POSS-II J films, merged with the brighter (mag. 18) star, and
I have since measured these films and obtain a position within a couple
tenths of an arcsecond of the MERLIN/Carlsberg location.  The details of
this are in an IBVS note that I've never got around to submitting, but which
Alon Retter has seen.
     At the time of course being able to supply the Central Bureau with a
position as good as it was was far better than what Peter Collins (the
discoverer) would have submitted, and it turned out that we supplied the
position to Dan Green before he had even been notified of the event.  It was
certainly good enough to lay a spectrograph slit on it without hunting around,
aiming IUE, etc., which was all anybody cared about in the first few days.

\Brian

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