An eyepiece is simply a precision magnifier. (Another name for an eyepiece is ocular.)

The eyepiece used with a telescope magnifies the image that is formed by the main optical system. There are many different kinds of eyepiece designs for various applications. The design and quality of the eyepiece can drastically affect the overall performance of the telescope system.

An eyepiece is usually described by barrel diameter and focal length. Common barrel diameters are 0.96", 1.25" and 2". 1.25” barrels are regarded as the standard for telescopes worldwide. Commonly available eyepiece focal lengths range from 2mm to 40mm. A shorter focal length eyepiece will be a higher power eyepiece when used with your telescope.

Dude!

Think of this, a Paracorr adds ~15% to the focal length, so you effectively have an f/4.6 scope. That's still very fast, and unforgiving of many eyepiece designs.

Pupil dilation is normally listed as 7mm under full darkness, but that's closer to 5-6mm at age 50. Any eyepiece that gives you a 7mm exit pupil would effectively waste aperture. To find the exit pupil, just divide an eyepiece's focal length by the scope's f-ratio (4.6 with the Paracorr).

Your most important eyepiece(s) will be in the 2-3mm exit pupil range, since you'll still get a decently bright image, but you'll enough magnification to get delicate detail on galaxies. Whatever eyepiece(s) you put in this range (9mm - 14mm for this case), I'd make these count the most. Think of it along the lines of the ball your roll down the bowling alley after you complete a spare.

Based on that...here's a few line-up suggestions, all assuming the Paracorr is in the focuser and the scope is operating as a 25" f/4.6. I'm not one for filling small "gaps" in a line-up, but I'd prefer to go with a 3 or 4 premium eyepieces that span a wide gap. If I was 50 years old, I would avoid any eyepiece that gives more than a 6mm exit pupil, and I'd prefer to keep the lowest-power eyepiece at a 5mm exit pupil or less.

Line-up 1 is to simply go with what I got:

23mm Celestron Axiom LX ($299 new, 5.0mm exit pupil, 127X)
13mm Nagler Type 6 ($290 new, 2.8mm exit pupil, 225X)
9mm Nagler Type 6 ($290 new, 2.0mm exit pupil, 325X)
Throw in a 2X barlow ($100 or less) to chase it all down, and you'll have 450X and 650X. Total price--about $1,000 new, and all 82-degrees.

If you want just a little wider field of view for the low-power end, how 'bout Line-up 2:

28mm UWAN ($350 new, 6.1mm XP, 104X)
20mm Nagler Type 5 ($450 new, 4.3mm XP, 146X)
13T6 ($290)
9T6 ($290)
2X ($100 max); total cost ~ $1,500

If you want *REALLY* widefields, and are willing to get by with 3 eyepieces and care to bend the rules a bit, try...

22T4 ($480 new, 4.8mm XP, 133X)
13mm Ethos ($620 new, 2.8mm XP, 225X, but 0.44-deg true field!)
8mm Ethos ($585 new, 1.7mm XP, 365X)
2X Barlow ($100 max, but now you'll have a "6.5E" and a "4E"), total cost--$1,800 new

I'm assuming the current Televue sale won't last indefinitely, so I was quoting the pre-sale prices. And I should warn you--an Ethos is like crack--you're addicted after the first "hit", and you gotta have that "fix". If you get one, you'll want them all.