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Dale Keller's 10 inch F 5.6


Dale Keller's 10" Newtonian Dale Keller built this 10 inch F5.6 newtonian reflector using Coulter optics. The full-thickness mirror was produced in 1980, when Coulter was known for their high quality. The tube is sonotube with shallow foam weather-strip baffles. The primary mirror is mounted in a homemade aluminum 9 point flotation cell. The 1.83 inch diagonal mirror is mounted in a Kenneth Novak holder with a homemade brass curved-vane spider. This size diagonal was selected to give an 18% (by diameter) obstruction of the primary mirror. This produces a high contrast image at the expense of the 100% illuminated field of view. The focuser is a 2 inch low profile helical type. The finders are an 8x50 straight-through and a telrad. Three handles are mounted around the tube near the focuser for convenience in pointing the scope. 

The telescope was optimized for visual use using Newt version 2.5 software. Newt is a Windows program which ray traces a newtonian telescope and helps you quickly choose the optimum diagonal size, focuser height and diameter, baffle positions, and many other things. 

The dobson mount was thrown together from scrap plywood 18 years ago with the intention of making a nicer mount shortly thereafter. That stayed on the to-do list for many years. (See the new and improved mount below.) The original teflon and Ebony Star azimuth bearing was replaced with a lazy susan bearing with an adjustable friction brake. This works fairly well - the adjustability is very convenient. The drawback is that it makes too much noise. It's embarrassing to have your scope squeak loudly at a star party. Oiling it helps, but also makes the dust stick worse. I would recommend staying with the teflon and Ebony Star bearings. There is also a friction brake on the altitude bearing. These brakes are wooden 1 by 2 boards mounted on a pivot with a knurled knob and spring to adjust them.


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