12 inch
I built my first Dobsonian telescope around an Orion Optics (UK) 12-inch f/4.0. Jan van Gastel (Jan van Gastel's ATM pages) stimulated me to start building telescopes myself and helped me with the design. Actually, it was partly built as exercise to see if I could make a decent telescope at all, and to get experience with a fast, f/4.0 optical system. It started with humble beginning, a small Dobsonian telescope.

Once I found out it operated well, I installed the Argo Navis digital setting circles. It stayed like that for a while, before I finally equipped it with the ServoCAT junior system. This telescope, however, has always been a 're-building' telescope. In all it has seen four different versions, of which the last one is shown below. This telescope has also been my travel telescope and has seen a lot of Europe.

All mirror sets from the described mono-Dobsonian telescopes are from Orion Optics. This first 12-inch was a revelation. It’s a 1/10 PV wavefront mirror, with a Strehl value of 0.990 (A very good review on this topic is from Royce). Star testing confirmed that it is really an excellent mirror. The beautiful wide-field views the optics delivered have been a class apart! I recall one night in particular, when I dragged the 12-inch up a mud road in the Austrian Alps, after days of rain. At 1700 meter the sky was incredibly transparent. I saw the Bubble Nebula for the first and only time ever. But what really made that night was M31. I simply couldn't get away from it, scanning the entire, incredible length of the galaxy with the 26 mm Nagler. The dark lanes just spat out of the eyepiece. A rare night of observing, that's for sure!

13 inch
An aperture close enough to include this one here. I built this telescope around one of Mike Lockwood's 13 inch f/5.0 mirrors that are part of the binoscope. It replaces the above described 12 inch, since I sold that telescope after I built the binoscope. I use the 13 inch at home, primarily to observe double stars. The sharpness of these mirrors are very good, so I enjoy using this telescope for that purpose. I operate the telescope with the Argo Navis system (not shown). It runs smooth and is very stable. The groundboard and rockerbox consist of merely thick multiplex. It suffices and makes the telescope rather compact and easy to set up.

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