Hello...I'm looking for an eyepiece to use for afocal photography on my ETX 80. Ideally, the eyepiece needs to have long eye relief and ideally a flat field and little to no distortion in an F5 telescope. One that also exhibits minimal blackouts would also be nice. Wide FOV isn't important. FL would be between 15 and 20mm. Price is also a factor, as I would like to keep it below $100 if possible.

With these criteria in mind, what would be good candidates? Many of the eyepieces I've found have eyecups that diminish the "real" eye relief...so removable or twist eyecups would be nice (It would be nice to leave it in place and merely have it sticking up a mm or so...makes a nice bumper for the camera lens. ).
Craig