Re Plossls, my experience has been that the longer the telescopes F ratio, then the better the image, so I respectfully disagree with the idea of negative coma.
However, I really dislike Possls below 15mm, as the eye relief is really too short because in part, I do not like my eyelashes touching and leaving marks on the lens.
Eyepieces that I favour generally have from 15mm to 20mm eye relief, at least a 60 degree field, do not weigh too much, and have a sharp image almost regardless of the F ratio.
Personally, I like the Radians (although the smaller focal lengths are a bit heavy), and I have a 13mm ethos (which is really uncomfortably heavy) which I also like.
Recently, I have taken some pleasure in trying to estimate the colour of the nova in Centaurus. I thought the radians gave a slighty false, warm colour, so out come a rarely used Meade 20mm SWA, which in my opinion is better colour corrected. So it can really be horses for courses.
At my age (58), I have become more fussy with eyepieces. I can remember being an enthusastic 13 year-old amatuer and both myself and a friend wondered why binoculars come with a fine focus for the second eye, as it always seemed in focus regardless of where we focused it. I wish my eye had retained that capacity to compensate, as getting that fine focus right is now very important requirement for me being able to see clearly. In a similiar vein, for general viewing, I used to greatly favour eyepieces that gave an exit pupil of about 5mm, now I prefer those with an exit pupil of about 3.5mm.
So it a nutshell, different eyepieces have come in and out of my favour depending on what I wish to use them for, and sadly, the state of my eyes, as I age.
I actually thought I had found the 'perfect' eyepiece when I brought a Unitron 25mm Kellner, some 44 years ago. I have found many perfect ones since, but I am still looking, as the improvements in my astronomical-lifetime have been absolutely amazing.
