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Hubble Space Telescope
ACS pointing patterns

ACS-HRC-DITHER-BOX
pointing patterns

This is a two-dimensional 4-point dither pattern, with the following allowable parameter ranges:

     Pattern_Number: 1 
       Pattern_Type: ACS-HRC-DITHER-BOX
    Pattern_Purpose: DITHER
   Number_Of_Points: 4
      Point_Spacing: 0.01 - 10.0  (arcseconds)
       Line_Spacing: 0.01 - 10.0  (arcseconds)
   Coordinate_Frame: POS-TARG
     Pattern_Orient: 0.0 - 360.0  (degrees)     
Angle_Between_Sides: 0.0 - 360.0  (degrees) 
     Center_Pattern: ?            (YES or NO)

The following versions of this Pattern_Type are projected onto the detector pixel space in the graphic above.
The default pattern has relative pixel coordinates
(0, 0), (5.0, 1.5), (2.5, 4.5), (-2.5, 3.0).
It is a parallelogram pattern designed for half-pixel sampling in both x and y, with overall dimensions large enough to help reject the larger detector artifacts.
     Pattern_Number: 26
       Pattern_Type: ACS-HRC-DITHER-BOX
    Pattern_Purpose: DITHER
   Number_Of_Points: 4
      Point_Spacing: 0.151
       Line_Spacing: 0.098
   Coordinate_Frame: POS-TARG
     Pattern_Orient: 20.07
Angle_Between_Sides: 63.58
     Center_Pattern: NO
POS TARG equivalent:  0.000,  0.000
                      0.142,  0.052
                      0.071,  0.119
                     -0.071,  0.067

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