Yesterday I finally received the last of the parts needed to adapt the Baader Hyperion Mark IV zoom eyepiece to my wife's Nikon Monarch 82ED spotting scope. I also received a Baader Ultrashort T-2 / 1.25" eyepiece clamp, a Telescope-Service short Nikon T-adapter and by chance I discovered I already had a Takahashi 2" / T-2 eyepiece holder. So, here are the results of trying to adapt a number of eyepieces to the Nikon scope.
First, the Baader Mark IV zoom is no problem at all to adapt directly to the scope by using two Baader adapter rings: part # 2454833, which changes the 2" female thread at the bottom of the eyepiece to female T-2, then part #1508025 which inverts the female T-2 to male T-2. The eyepiece can then be screwed directly into a Nikon F or Nikon DSLR T-adapter (same thread as T-2).
The T-adapter should be mounted on the scope before screwing the eyepiece into it. Just remember that the white marks on the T-adapter and the scope should NOT be aligned at the start. To find the correct starting position for the bayonet note that one of the three bayonet flanges is wider than the other two, That one should start pointing down toward the locking button on the scope, then rotate counter-clockwise until the bayonet clicks and locks. There should be plenty of focus past infinity with any normal depth T-adapter.
For adapting 1.25" eyepieces to the scope I tried a combination of the Baader Ultrashort eyepiece clamp, the Baader female to male T-2 inverter and the Telescope-Service short Nikon T-adapter. I don't know of a shorter generic 1.25" eyepiece clamp, but in this case it adds about 20mm to the length. Baader claims it adds only 12mm to the "focal length", but apparently that's because they don't count the tube that contains the female T-2 threads. The short T-S Nikon T-adapter adds only about 1mm to the length for a total of 21mm.
I haven't bought any astronomical eyepieces in quite a while and my collection includes only a few that are likely to be of general interest. Of those I found I could easily reach focus with a Televue 13mm Nagler Type 6 and a 19mm Panoptic. I was not able to reach focus with a Pentax XW 14mm or a Baader Hyperion 17mm. Both were tantalizingly close. Probably missing by only 1-2 mm. Televue claims that all their current eyepieces are parfocal, so it could be that any current Televue eyepiece will reach focus in the Monarch scope with the adapters I'm using.
I discovered that I already owned a Takahashi 2" eyepiece holder with female T-threads (right photo below), so I tried that with the three 2" eyepieces I have. Only a 48mm Brandon could reach focus. Neither a 22mm Panoptic nor the 17mm Hyperion (using the 2" barrel) could, but the Hyperion was closer than when paired with the 1.25" eyepiece clamp, less than one diffraction ring from reaching focus on a star for my eye. The Tak eyepiece holder adds about 40mm of length, so a little shorter one would certainly have worked with the Hyperion and possibly the Panoptic.
My conclusions are that the Baader Mark IV Zoom is easily adapted to the Monarch scope, but only some 1.25" eyepieces will reach focus and making any of them work requires the use of the T-S short Nikon T-adapter. It would certainly be quite feasible for Baader, Nikon or someone else to make a short adapter that could accommodate nearly all 1.25"eyepieces, like what is available now for the Kowa 77/88mm scopes.
Henry
