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My Steampunk Telescope #3: Balancing Act

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Blog entry by TelescopeMaker posted 1252 days ago 1746 reads 0 times favorited 3 comments Add to Favorites Watch
« Part 2: How it fits together Part 3 of My Steampunk Telescope series Part 4: Applying head knowledge. »

I’ve managed to work some more on my Telescope. One of the things that is very important in a telescope is that it be balanced. The last thing you want to happen is to point it at some pretty double star and say to your friend, “Take a look!” and have the scope move eight inches toward the ground.

The center of balance determines the size of the trunnion bearings. So until I know where it balances, I can’t know the size of them. Before I determin the balance, all the parts of the telescope must be assembled. Up to this point I have been running into technical difficulties.

Mathmatically I calculated where the balance point should be, but when I did some rough measurements, it was beginning to look like they were way off. I decided to simulate the balance with a mock-up of something similar to what I would eventually do.

And today, with the completion of the final part, I can report that the balance of the telescope is very close to what I predicted it would be.

DSC03239

The last part I had to make was a baffle to keep stray light from street lamps and houses out of my field of vision. The baffle needed to be very light weight so that I wouldn’t have to add extra weight on the other side of the pivot point to balance it out. I chose to use a polystyrene “for sale” sign. It was cheap, came in 18” x 24” size and is easily molded on a vacuum mold over a form. The form is a saddle shape that I placed on top of a vacuum box (it’s similar to a down draft table, and in fact, that is what I will use it for from here on out). My shop vac attached to a hole in the sides sucks the hot plastic For Sale sign over the top of the mould, and presto-change-o I have the shape I need. Cut it with a utility knife, paint it black so it doesn’t reflect light, and I have a light baffle.
DSC03234
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Here is a picture of my telescope right before adding the baffle to it. The scope is resting on a temporary U shaped fork. it balances on those two 3/8” bolts you see. The pipe is an aluminum tube. The main mirror fits in the large 12” dia opening.
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Here is a picture of the business end with the round eyepiece holder. The rectangular thing to the right is a unique finder scope, sometimes called a reflex scope or a 1X finder.
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Here is what it would look like if I had thought to take one final picture after assembling it all. I’ll get a real one next time.
topend

At the rate I am going, I should be done with this thing in February sometime… Then I can finally make my workbench :) Its going to be a “jack-bench”.

Edited on 11/15 to include these four pictures of the top end as well as the main mirror installed. The main mirror is not silvered yet because I am still adjusting it’s paraboloidal shape.

The top end with eyepiece in the focuser and the diagonal mirror with the light baffle:
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Ditto from another angle:
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The whole enchalada from the Moon’s point of view:
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Main mirror in the mirror box:
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As it turns out my calculations for the balance point were right on… Physics matches reality and that’s a good thing. :)

-- Telescope Maker, Woodworker, Brewer, Gizmologist, Gardner, Lawn Mower



3 comments so far

View Robb's profile

Robb

660 posts in 2436 days


#1 posted 1252 days ago

I love the diversity of workmanship here on LJ! Thanks for sharing a unique project.

-- Robb

View JerryL's profile

JerryL

45 posts in 2550 days


#2 posted 1251 days ago

So is that a 12” F6 or so? It’s difficult to tell the focal length from the pics. I also really like the idea of the asymetrical bearings – I think that’s what I see in part 2. That’s the first time I’ve ever see that. I’ll also add that you will love that HC-2. I have one and it’s a dream to use.

-- Jerry L.

View TelescopeMaker's profile

TelescopeMaker

64 posts in 1523 days


#3 posted 1249 days ago

Don’t know why my responses didn’t make it through the other day. But anyway, Thanks Robb. I feel the same way.

Jerry, yes, it is a 12.5” f/5.5. They are asymmetrical – good eye. The HC2 is nice, and it is about the lightest one around. For those that don’t know, HC-2 is the model number of a brand of focuser. It stands for “Helical Crayford”. It is a type of focuser that won’t have any backlash like a cheap rack and pinion highschool microscope has.

I have teh whole thing torn apart now. I have taken the mirror box and rabbeted out the edge of the plywood top and bottom by 1/16” to make way for binding like on a guitar. Hope it works out. it was easy enough to do that part at least.

-- Telescope Maker, Woodworker, Brewer, Gizmologist, Gardner, Lawn Mower

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