Home › Forums › General Discussion › Martin Mobberly and his 19.3″ (49cm) f/4.5 monster › Re:Martin Mobberly and his 19.3″ (49cm) f/4.5 mons
Posted by David Arditti at 20:16 on 2010 Feb 21
Interesting that Martin says his 19" had a wormwheel as accurate as that of a Paramount. I am surprised, as the 10" AE Dall-Kirkham-Dall had a very inaccurate drive in its C-type GEM, with a PE of about 1 minute, and I have read elsewhere on the web a comment about problems with PE on AE drives. It seems that they varied a good deal. Also the C-type GEM had a very weird constructional idea whereby the worms rotated in holes actually bored through the main castings of the mount, which could never work well, as there was no way to tune the placing of the worm with respect to the wheel. Other manufacturers of the time, e.g. Irving and Fuller, at least had the sense to make the worm casting a separate section. The mount of the 10" Cassegrain was really its most unsatisfactory feature. Another problem was the lack of any method of clamping the axes, which made the telescope very hard to handle. Again, Irving and Fuller had the sense to provide clamps.Richard McKim’s telescope is I believe a hybrid construction from several different sources, though the mount clearly shows AE components, and I think the optics are by Hysom.