Setting regions of an image to bad can be done graphically using the GAIA display tool (SUN/214) which can also create an ARD file to describe these regions. Alternatively KAPPA (SUN/95) also provides applications for this task (see ZAPLIN, SEGMENT ARDGEN and ARDMASK).
The capabilities of the ARD option (which uses considerably less disk space than the ``image with bad regions'' option and hence could form part of a `database') are described below (for more details see SUN/183).
The shapes of regions which can be defined are specified by the following KEYWORDS:
BOX, CIRCLE, COLUMN, ELLIPSE, LINE, PIXEL, POLYGON, RECT, ROTBOX, ROW
Regions are specified using the keywords suffixed by the following information:
- BOX(XCENTRE,YCENTRE,XSIDE,YSIDE)
- CIRCLE(XCENTRE,YCENTRE,RADIUS)
- COLUMN(COLUMN1,COLUMN2,COLUMN3...)
- ELLIPSE(XCENTRE,YCENTRE,SEMIMAJOR,SEMIMINOR,ANGLE)
- LINE(XSTART,YSTART,XEND,YEND)
- PIXEL(XCENTRE1,YCENTRE1,XCENTRE2,YCENTRE2...)
- POLYGON(XCENTRE1,YCENTRE1,XCENTRE2,YCENTRE2...)
- RECT(XCORNER1,YCORNER1,XCORNER2,YCORNER2)
- ROTBOX(XCENTRE,YCENTRE,XSIDE,YSIDE,ANGLE)
- ROW(ROW1,ROW2,ROW3...)
The angles are measured X through Y positive.
A sample ARD description follows:
#
# ARD description file for bad regions of my CCD.
COLUMN( 41, 177, 212 ) # Three bad columns
PIXEL( 201, 143, 153, 167 ) # Two Bad pixels
BOX( 188, 313, 5, 5 ) # One Hot spot centred at 188,313
ELLIPSE( 99, 120, 21.2, 5.4, 45.0 )
# Polygons defining badly vignetted corners
POLYGON( 2.2, 96.4, 12.1, 81.5, 26.9, 63.7, 47.7, 41.9,
61.5, 24.1, 84.3, 0.0 , 0.0, 0.0 )
POLYGON( 6.2, 294.3, 27.9, 321.0, 52.6, 348.7, 74.4, 371.5,
80.0, 384.0, 0.0, 384.0 )
#
But you should use the ARDGEN application to
produce these files.
CCDPACK