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SM60II Richview - Purpose of front threaded element?

Posted: Thu Jun 02, 2016 10:42 am
by pmlogg
When trying to adjust contrast with my pair of SM60 IIs the threaded ring on the front of the rear SM60 II (forward of the Richview tuner) loosened slightly. I had wondered whether these were removable - they look so similar to the SM60 double stack adapter.

When finished viewing I split the pair of etalons and removed the ring that had come loose. Testing it with an SM60 double stack adapter (not needed with SM60 IIs) I found that it fitted to the front of it. So the threads of the part I'd taken off are the same 82mmx1.0mm front and back, matching those on the rear of both the T-max tuners of the SM60 and SM60 II etalons. So the ring is a sort of extension tube.

That being the case what is purpose of these threaded rings on the front of the SM60 II etalons? Could they be dispensed with, just screwing the T-max tuner of the front etalon to the Richview tuner of the rear one? Similarly, the front lens cap fits the thread of the Richview tuner less that front element. So it doesn't seem necessary for that either?