Description of various C3 vignetting correction files at NRL:

C3clearvig_990812.fts

• GIF
• Derived by Matt Moorman using star brightness and position. The 3 non-pylon quadrants are a constant, theta-independent radial function. The pylon quadrant was derived differently, and has a significant discontinuity at the quadrant boundaries
• Occ_cntr (center of revolution) is 516.3, 529.5.

• GIF
• Derived by Nathan Rich from stars. Attempts to fit separate exponential functions to the occulter and edge at discrete angles (theta) described here.

• Original vignetting correction computed by Clarence Korendyke from pre-flight data (I think).
• GIF

• Similar to C3clearvig0.fts with an inverse-r scaling (radial filter)
• GIF

• Vignetting correction from LAS/Antoine Llebaria, c. 2000
• GIF

• C3clearvig_990812.fts with the pylon quadrant removed
• GIF

• The LAS correction with no pylon multiplied by C3pylonvig_010110.fts
• Center is 518.5, 529.5
• GIF

• C3clearvig_nrl.fts truncated at max 50 and with some smoothing applied
• GIF

• A pylon vignetting correction derived from a monthly background model image:
• a. find model where football is near horizontal (3m_clcl_970101.fts???)
• b. rotated 3.56 degrees and shifted so occulter center is at 511.5, 511.5
• c flip image about center
• d. replace bottom of a. with bottom of b.
• e. divide d. by a.
• f. do a ROI to pick out pylon and make everthing else 1.0
• g. smooth
• Center is 518.5, 529.5
• GIF

• From Jeff Morrill, prior to Sept 2002
• Center is 516.4, 531.15
• GIF

• From Mike Andrews, prior to March 2002
• Same as C3clearvig_990812.fts (M. Moorman) with pylon quadrant scaled to the adjoining quadrants
• GIF