12.5" Scope Redesign

“A scope you make is never really done”

Ron Ravneberg warned me. That phrase echoes in my mind as I stay up late thinking about ways to improve my telescope. Every path I go down leads me to the same conclusion: time to try something new. The two telescopes that I have made are both based on a sphere as the interface between the mount and the telescope. This is a design that MAG1 Instruments and Edmund Scientific used for their commercial telescopes. While I really like this design, the limitations of it are hard to design around and every time I conquer a new challenge, another one is staring me in the face. Now, it is not the challenge that is frustrating me, but the cost involved to overcome that challenge. The money that I have spent on improving my ballscopes could have allowed me to purchase all of the items I really want on a telescope (like a Moonlight Focuser, anti-dew, right angle finder, etc.)

The current challenge is that the ball thickness is just not thick enough and the ball gets out of shape from some of weight of the scope (and also the stress involved in my technique of using pressure and friction to keep the mirror cell in place). This manifests itself at the eyepieces by the telescope rocking in certain orientations (about 30 degrees away from zenith). There are also alot of vibrations being enhanced by this (I may be barking up the wrong tree here on that one, but it is all I got to go on at the moment).

So I made a hard decision to start a new design based on good old two axis dobsonian mechanics. Originally, I was going to purchase either a Telekit from Astrosystems or a kit from www.dobstuff.com, and those are some great kits. But what fun is it to build someone else’s design? Not fun at all! (Plus, I just don’t have the money).

The current secondary ring is just fine. In fact, I love the look of a single ring: nice and minimalistic. The struts are also fine (good job Moonlite on such a great product). So I will be reusing the secondary ring and struts. No need to redo those. I am on the second version of the secondary ring and it is pretty light.

The bottom end will be a hybrid type of mirror box of sorts. Part of it will be a ring and the other part a box. The mirror box will be opened to allow for cooling (an idea I borrowed from dobstuff.com). 18″ bearings for a nice smooth action, and I will probably paint it black with some type of fleck paint on some parts to give it some character.

Here are some preliminary designs I came up with in Google Sketchup.


~ by jhissong on 2009/05/01.

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