“ Brand: Revelation / Type: Precise focuser for newtonian telescopes „
One of the most critical factors in astro imaging alongside good tracking is a decent focus, replacing the factory installed run of the mill rack & pinion focuser on my 12" Dob was one of the first modifications I made to the telescope and all things being equal, was a worthwhile one. I say all things being equal because the Revelation has its share of negative points despite getting the job of precise focus done.
Firstly and most importantly, the 1.25 inch adapter (where you insert eyepieces) is absolutely useless!!! It is way too tight so as to make regular eyepiece insertion/withdrawal impossible. To secure or remove a camera/eyepiece you must first loosen the tightening screw that anchors the 1.25" adapter to the focuser then withdraw the eyepiece with the adapter still attached like a ballerina's skirt. Then you have to twist the adapter off with a considerable effort. It's unconscionable that such a basic and fundamental error should have made it all the way through to production.
It has to be said though that once you get used to this rather absurd design flaw and the elaborate process of twisting your eyepieces in and out becomes second nature the focusing action itself is very precise for a £120 focuser. As the Crayford design uses a smooth steel roller and pressure to achieve traction (where the traditional R&P focuser uses toothed gears) the focus is wonderfully smooth without any of the wobble or bumpiness associated with the cheaper rack & pinion focusers.
Focus is buttery smooth not only with the large knurled rubber cups that operate the regular action but also with the small button sat on the right hand side that is responsible for the 1:10 fine focus. Getting yourself roughly to the point of focus and finishing off precisely with the fine 1:10 control is an extraordinarily satisfying and tactile experience.
Something to watch out for, make sure you have the correct base plate for the focuser to sit on, if not (as was the case for me) you will be left with two conspicuous gaps either side of the focuser, which as well as being aesthetically unappealing will let in loads of dust unless covered with black tape or some such.
Despite the problems with the 1.25" adapter I would recommend the revelation for the simple reason that it's hard to find a decent focusing action within the budget crayford category, any frustration encountered with the adapter is offset by the super smooth and crisp focus achieved.