I was testing the Russell 50mm SP tonight. Scope was a SV80 refractor with the TMB LOMO triplet lens (80/480).
Early results equal or better than the 55 Plossl, and the T2 threaded adapter is worlds easier than the DioptRX clamp mechanism. If Tele Vue ever does a dedicated NV eyepiece, I sincerely hope they go T2 threads!
55mm FOV is slightly wider (as expected) however, the amount of "clean" field may be slightly less than the Russell. Close, will need more testing, especially with different scopes.
Tested on star fields only, no filter work. I will expect the Tele Vue to be very slightly brighter (by the math). It will be interesting to see if the difference jumps out visually.
Took some photos, but they are more a measurement of my photo (in)ability rather than the two eyepieces. I gotta read Ray's article again ;-) All unguided 1 second iPhoneX shots, ISO 100.
1) Russell 50, centered on Owl Cluster, NGC 457. (Corresponding TV 55 image not well focused, user error.)
2) Russell 50, centered on Navi (Gamma Cass). Even with no filter, Gamma Cass Nebula obvious.
3) Tele Vue 55, same field as #2. Note difference between faint stars in center and edge.
Edited by Jeff Morgan, 13 February 2020 - 12:51 AM.