Re-potting a Dob

[Tog]

I have a 16" dob and a car that is not too much larger. I haven't used the scope in 2 years because there is no way fo rme to get it further than I can carry it. It's one of the Old Snotube Meades with the 33 inch diameter base.

Well, things have changed. The boss where I work managed to talk the owner into springing for a 3 axis CNC machine that does wood. I've been told that if I have any projects, to draw them up and he'll cut them out. I want to convert my Dob to a Truss, but I have some questions about it.

The website I first looked at that had the things to hold the poles is gone. That's my biggest issue. How to mount he truss in a way that is both idiot-resistant and practical.

My second issue is with the secondary. I have a program for designing scopes and the secondary I have is huge compared to she this says I need. If were to post the numbers I get would someone be able to tell me what I actually need, and more importantly, why?

[hhEb09'1]

My second issue is with the secondary. I have a program for designing scopes and the secondary I have is huge compared to she this says I need. If were to post the numbers I get would someone be able to tell me what I actually need, and more importantly, why?I can't help, but I'd like to watch. Let's get started, post the nubmers :)

[Tog]

Okay, due to cost, I need to re-use as much as possible. This will include the main Mirror and cell, the focuser (for now) an possibly the secondary (which I want to avoid).

The main mirror is 16 inches at f/4.5. Focal length is listed as 1830mm, or 72 inches.

The secondary I have is 4 inches on the small axis. It's heavy enough that it actually bend the 1/4 inch rod that held it in place. Id like to step down to a 3.1 if possible.

The Focuser is the standard Meade, but in it's current set up, I have to add a short Barlow tube with the lens removed to make it long enough to reach focus.

The plan at this point is to take the main mirror, cell and all and mount it in the bottom of the lower box. All I need for this is a big hole in the bottom and some bolts.

For the upper assembly, I had planned to go with an octagon shape with a 17.5 inch hole, making the focuser about 3 inches further up the tube than it is now.

I have a program called NEWT, which basically does all of the math once you put in the specs, but I'm not sure I know what the specs will be. Is 17.5 large enough for a 16 inch mirror? Can it be any smaller?

What is the smallest secondary I can use and not short myslef?

What is the best type of wood to use, and what type of surface should I use on the base? I had though the azimuth section would work well with a chunk of Formica counter top.

Having access to this machine will make a lot of stuff that was out reach before possible since it will be able to make the exact cuts I want.

And blast that program... You can't copy from it.

[Veeger]

Sixteen inches??? Wow. Just out of curiosity how much does that primary weigh? Your secondary is bigger than my first telescope primary.

[Tog]

Sixteen inches??? Wow. Just out of curiosity how much does that primary weigh? Your secondary is bigger than my first telescope primary.

the total on the upper tube is just about 100 pounds. The tube is basically cardboard, so I'd guess the mirror runs about 80-85. The base of the thing is 75 pounds by itself.

You have to really want to use it to take it out.:p