ASTROMETRY OF THE HUBBLE DEEP FIELD FLANKING FIELDS
	---------------------------------------------------

	By the DEEP team, UCO Lick Observatory, UC Santa Cruz


In order to create slit masks for multi-object spectroscopy of
galaxies in the HDF using the Low Resolution Imaging Spectrograph on 
the 10-m Keck telescope, we derived self-consistent astrometric
solutions for all the Flanking Fields and the central HDF.  This was 
done as follows:

1) 49 bright stars appearing in both the digitized Palomar Sky Survey
and in the much deeper KPNO 4-meter R-band CCD image obtained by Peter 
Eisenhardt were used to derive an astrometric solution for the R-band
image; the r.m.s. residual of the solution was 0.4 arcseconds (due to
errors both in the Digital Sky Survey and in our solution).

2) Typically 40 compact objects (stars and compact galaxies) with
I(ST)<23 per Flanking Field and in the HDF also appearing in the KPNO
4-meter R-band image were then used to determine offsets of the FF's
with respect to the HDF.  The astrometric solution in the header of
the HDF itself was confirmed to be very close, though not identical,
to the DSS solution (offsets << 1 arcsec), and to be consistent from
WF chip to WF chip within the HDF.  The original astrometric
solutions for the Flanking Fields were confirmed to have only
translational offsets, with no significant rotation, with respect to
the HDF.   The offsets given below are all referenced to the HDF, not
the DSS.  

These offsets are in units of arcseconds in the sense 

   offset = (new RA, DEC) - (old RA, DEC from solution in FF headers)

Thus, to obtain coordinates consistent with the HDF coordinate system,
these offsets should be ADDED to FF coordinates given by, e.g., 
"imexamine" or "xyeq" in IRAF.

After correcting all the FF's to the reference frame of the HDF, the
overall astrometric solution of HDF+FF is self-consistent to a level
of 0.2 arcsec r.m.s.


   Field  R.A.   DEC   r.m.s.
          (")    (")    (")
   -----  ----   ---   ------
    ie   -0.07   0.25    0.29
    ne    1.11  -0.10    0.42   
    oe    0.17   0.40    0.56  
    se    0.57  -0.32    0.44  
    iw    0.02  -0.05    0.23  
    nw    1.09  -0.25    0.36 
    ow   -0.05  -0.26    0.31  
    sw    0.86  -0.51    0.25  


These astrometric solutions were used successfully for our LRIS Keck 
observing run in April 1996.
 

 Questions:

 James Lowenthal    james@ucolick.org
 Rafael Guzman      rguzman@ucolick.org
 Jesus Gallego      jgm@ucolick.org