It has finally dawned on me why I was having problems with 'exit pupil' on the Coronado PST. I could not understand why, when using a higher power with good eye relief (eg Barlow and 15mm Plossl,) the exit pupil made life difficult for me.
Even though I looked down where the EP fits I did not take into account the very small (2 - 3mm) exit aperture on the PST - until prompted by a mate!
So, unlike a normal scope where, say, the star diagonal is open to 1.25" all the way this is closed allowing only a very small light source. I bought a 9mm EP with excellent eye relief and still had problems. Calculated that the exit pupil should be .9mm - easy for me. I have now settled for an Orion 9mm 'Expanse' EP with 66 degrees FOV and love it.
Hope that clears it all up!
Cheers!
Bert