From: Alex Conley (aconley@panisse.lbl.gov)
Date: Wed Nov 06 2002 - 15:13:20 PST
I've looked into SuF02-007/074. Naoki is certainly correct: they are the
same object. It appears that, sadly, SuF02-007 is right and SuF02-074
is wrong. SuF02-074 was riiight on the edge of the chip in the
subtraction, so presumably the USNO/APM solution diverged.
On a positive note, the offsets and coordinates for finding charts both
agree pretty much perfectly, despite being prepared with different input
coordinates and different images. This is encouraging. The bad news is
that the same stars give different magnitudes in the different finding
charts. This is why you can't trust APM/USNO magnitudes very well on
really deep images like these. Doh!
So -- looks like SuF02-007 can't be observed by Gemini. Sorry.
Alex
On Wed, 6 Nov 2002, Isobel Hook wrote:
>
> Hi Saul,
> That is correct - we did find a guide star for 074 but not 007. We are
> using the positions from SNtrack, which I am assured should be good to a
> few arcsec. If they are not, and the difference is so large that it makes
> the difference between thinking we have a guide star or not (i.e greater
> than about 30" error), then we will have to redo all our Phase-II
> preparation. I am still in my hotel now but I'll have another look at
> these two when I get to the office.
>
> Isobel.
>
>
>
> On Wed, 6 Nov 2002, Saul Perlmutter wrote:
>
> > Hi Isobel,
> > Is it true that you found Gemini guide stars for -074, but not for
> > -007? These are the two that Naoki pointed out are really the same
> > candidate, with essentially the same finding chart, so I was wondering
> > if when you check for Gemini guide stars you might be using the coords
> > from the tiles, rather than the (accurate) coords from the finding
> > chart.
> > Also, please confirm that you _do_ in fact have a good Gemini guide
> > star for this one, so I know not to get another telescope to do it.
> >
>
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