FIT_LIMB is a modified version of SXT_CENTER. It currently requires that you know the
pixel size of the image which is being processed (although the pixel size can be
derived by calling FIT_LIMB multiple times with different pixel sizes until
the diameter of the solar limb outline matches the image). It allows fits to a partial solar limb.
A sample call to FIT_LIMB is
IDL> fit_limb,img,x0,y0,/int,pixel_size=3.97
where it assumes that you have the image to be fit in the variable img.
The /int enables the interactive selection of the initial guess of
the fit. It is very important that the first guess be very close. pixel_size=3.97
specifies the pixel size in arcseconds. The E/W and N/S sun center coordinates
are returned in x0 and y0. These values must be inverted since we want
the corner coordinate relative to sun center.
IDL> corner2 = [-x0, -y0]