TeleVue & Trapezium
Last night I spent over a half-hour studying the Trapezium, and assessing the differences between the Nagler 7mm and the Radian 4mm, in both the APM 152 & Dakin 4.
Over the years I've been skeptical of TV eyepieces in vintage long refractors. I figured that all those lenses had to hurt contrast, and that my old fracs were better served with quality simpler eyepieces. As usual, my findings present a more complicated view.
Since the APM isn't a Classic, all I'll say about it was that I saw 6 member stars A-F, with several eyepieces. In the Dakin, I couldn't break out E, so I saw A-D + F. The Nagler gave the better views of the cluster; the Radian gave the most detailed view of the nebulosity. However, the background sky was blacker in the UO HD 9mm / 6mm & spectros Plossls 7.5mm / 5mm than in the TV eyepieces. The PL7.5 performed similarly to the Nagler 7 -- much closer than the Orthos. (For planetary observing, the Nagler is often a better choice than any of my other ~ 7mm eyepieces. I think the Radian will be the same.)
Hunting faint fuzzies with the Dakin, I used the Meade RG 20mm Erfle to locate both M65/66 & M81/82, then switched to the Nagler 7. The views were nicely framed by this TV eyepiece (and much better with it in the 6" ED!).
Would I plunk down the $$$ for brand new TV eyepieces? Nope. Like the Takahashi & Vixen gear, TV are well-made, and the owners tend to take good care of them. Buying used is the way to go.