Why? You only need to know 1 eyepiece and all the others can be found in 1 second by turning the top until the eyepiece is in focus.
Explore Scientific says their 20mm 100° eyepiece has its focal plane 15.20mm above the shoulder on which the eyepiece sits.
Since the working distance for the Paracorr II is 56mm from lens to focal plane, it is impossible to optimize the 20mm ES 100° because it cannot get close enough to the lens to be at its optimum position.
So, the only thing to do is to use the Paracorr at setting A and realize it is not optimum, but you cannot lower the top from there.
ES says the 5.5mm x 100, 9mm x 100, and 14mm x 100 are all parfocal and all have their focal planes 3mm below the shoulders they sit on.
Let's see if that makes sense. TeleVue says setting E is the 0 point for the lens, and is 60mm from the bottom of the tunable top measured on the outside.
That represents the point 56mm from the lens, internally. So an eyepiece with its focal plane 15.2mm above the shoulder would need 15.2mm of additional in-travel of the tunable top to get to the optimum distance from the lens, but setting A is only 10.16mm below the zero point. So, I am correct the 20mm ES cannot be moved into an optimum coma correction position in the Paracorr II, and setting A must be used. At least 90+% of the coma will be removed.
The shorter focal lengths of ES 100 will require 3mm more out travel than that due to their focal plane positions, so that would be exactly 0.12" farther out, which is setting F (actually F+0.02").
If you insert one of those eyepieces, move the top to setting F and focus, every other eyepiece in your collection could have its optimum setting discovered merely by focusing the scope using the tunable top instead of the focuser.
ES says, "Field stop positions below the end of the (upper) barrel (i.e. shoulder) are positive (because you have to focus outwards), positions above the reference surface are negative (because you have to focus inwards)." Their focal plane positions are listed on the attached sheet. It looks like most of their eyepieces are parfocal.
Edited by Starman1, 29 March 2018 - 07:47 PM.