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When converting between pixel value and angle the following steps are
taken.
- Determine the pixel address for the center of the sun. SXT_CENis used to derive this value. It will read the ATT database by default,
but can use the commanded value if the /CMD option is used on the
call to CONV_P2A.
- Determine the roll. SXT_CENreturns this value too.
- Perform the simple math to convert from absolute pixels to an
angle relative to the sun center.
Some sample calls are:
IDL> ang = conv_p2a(pix, date)
IDL> ang = conv_p2a(pix, date, /cmd)
IDL> pix = conv_a2p(ang, date, /cmd)
The date is required in order to determine the location of the sun on the CCD and
the roll angle. The S/C roll angle and S/C pointing is taken into consideration, but
the solar B-angle is not taken into account.