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A Classic Richard Berry 10 inch f/6 Dobsonian

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#26 clamchip

clamchip

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Posted 27 July 2020 - 09:59 AM

My guess would be the sillycone has distorted the mirror.

That's exactly right it did.

Its amazing a big hunk of glass can be so sensitive.

The astigmatism is gone now. I need a fan, it never did equalize this morning.

After a hour the stars were still not sharp enough for Mars.

I decided not to wait for the Martians to clear the cedar grove.

The mounting moves extremely well. If anyone is looking for a good design

this is it.

Mr. Berry's book is still available:

https://www.willbell.com/tm/tm2.htm

 

Robert


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#27 clamchip

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Posted 27 July 2020 - 04:33 PM

Needing a fan is nothing new here at my place.

6" mirrors can reach equilibrium and even maintain this state through the evening.

8 inch things get iffy, 10 inch forget it except for rare nights.

I'm using a fan I had already built. That's a bird feeder shell catcher you see.

We have those on some of our feeders to catch the waste, otherwise our dogs eat 

the moldy bird seed.

I bent some chain links into hooks and used these in the mirror stop screw locations.

I added silicone tubing to the collimation screws for vibration isolation.

You can see in the photo if I need to touch-up collimation it's easy enough to pull the

fan away to reach the wing nuts. 

Robert

 

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Edited by clamchip, 27 July 2020 - 04:46 PM.

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#28 clamchip

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Posted 28 July 2020 - 05:33 PM

I've decided to continue the restoration with the Cave primary cell.

A slight deviation from the original published plans.

I decided I like his front tube ring, and since I will no longer be using 

a plywood cell/rear ring I'm making a rear ring to match the front.

I cut a 3/4" x 1/8" fir strip, soaked in water and bent around the bucket

a few times and will leave it to dry.

Look at that sky, that means a morning on Mars. I'm all set now, no

more astigmatism, and a fan.

Robert

 

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