Adjusting the Image Pixel Scale
              (Button Selection from the Adjust Position Widget)

    The purpose of this widget is to modify the pixel scale of the
current reference image.  If the pixels are not square, the user
may rectify them by resampling the pixels in the Y direction to the
size of the pixels in the X direction.  The user may also apply any
arbitrary factor to the pixel scale.

Setting the Input Pixel Size:  IDP3 attempts to identify the Instrument
from the image header (INSTRUME, CAMERA, and DETECTOR keywords).  If
the Instrument/Detector is NICMOS-1, NICMOS-2, NICMOS-3, STIS-CCD,
WFPC2-1, WFPC2-2, WFCP2-3, WFPC2-4, MIPS-1, MIPS-2, MIPS-3, MIPS-4,
MIPS-5, IRAC-1, IRAC-2, IRAC-3, or IRAC-4 the x and y pixel scales
are populated from tables in the procedure, where all instruments
except NICMOS have a single value.  NICMOS values are populated as
a function of date.  If IDP3 cannot recognize the Instrument/Detector
(no appropriate keywords present in the header or name not recognized)
the user may select it from the pull down list from the Select button.
If the Instrument/Detector is Other, the user must supply the input
pixel scales.  If the header of the current reference image has a
valid set of World Coordinate parameters, the pixel scales may be
computed from these parameters.

Pixel Scale Factors:  The user may apply an arbitrary scale factor to
the x and/or y pixel scales for the output scale factors.  

Setting the Output Pixel Size:  The user may select the desired name
of the output Instrument/Detector from the pulldown list of the Select
button.  If the desired output instrument/detector is any name in the
list besides Other, the values are populated from the internal tables
as in the input.  If the same instrument is selected for the output as
the input, both pixel scale values are set to the x pixel scale value
which will cause the pixels to be rectified by scaling the Y axis to
the X axis.  If the desired instrument/detector is not in the list
the user must select Other and populate the pixel scale values himself.

Applying the Pixel Scale:  Once the input and output pixel scale values
are populated the user may apply the correction or cancel.