dome

Ever since I was a kid I’ve dreamt of an observatory of my own, I think that’s every astronomers dream. Not having to carry around your telescope. You probably already know that having to drag your scope out and in every night is most likely to kill your interest.

But I did not want this to happen so I began study different types of observatories and believe me there are as many different types as there are amateur astronomers. There are some really interesting homepages devoted to building observatories that I’d like to share with you

Take a look at my links page to find out more.

By mere chance or shall I say that faith brought me to the construction drawings by Joe Garlitz and in a blink of an eye the future was set, this was it !

The plans were for a geodesic dome observatory, for those not familiar with this it’s like a football cut in half.

But, there is always if. It’s a construct it yourself project.

Okay, I’m a prototype maker and model builder and usually I construct various things, but was I really up for a challenge of this magnitude?

My father used to say \”if you never try you will never know but if you’re to chicken out you’d better never try\”

So with this in my mind I plunged into the unknown knowing only that I had to make it.

And I’m glad I did and never hesitated, sure there were some problems and some difficulties.

Too bad my father isn’t around to see it, I think he would have been proud (of me not chicken out) and of the observatory that I made.

On the following pages I will describe in detail how I did it, witch material I used and what I could have done better.

All for those of you who wants to build one.

 

 base structure

 

With the construction of the base structure I had to remember that I live in northern Europe and that the climate is quite harsh for 5-6 month .We have subzero temperatures , a lot of snow and sometimes blizzards.

Therefore, whit this in mind I had to make it well insulated and very tight so that snow and water could not get through it.

If you live in better climates some of this points mentioned are totally unnecessary, but this is totally up to you

For the construction of my dome I started quite appropriate with the base structure, as I could not build it totally round I opted to make it as an octagon.

First I casted concrete piers on witch to place the construction then I began with the floor, this is made as a separate section much resembling a wheel

I then placed the wall skirts, the wall is 50 cm high but depending on your type of scope it could be higher or lower.

Between the inner walls and the outer facade I put 10 cm of insulation.

It must been said that there is no drawing for this bas structure at Joe’s homepage but if you want one just mail me.

With the base construction done I placed a base ring on top of it (this is the base ring mentioned in Joe’s drawing for putting the dome on) this means that I had to make two rings one lower to place on the base structure and one upper to place the dome on) these were made of 20 mm furniture plywood (10 layer plywood extremely durable) and painting it with one layer of boat epoxy plastic to prevent it from rotting.

Remember that working with epoxy is hazardous and you have to wear protective masks also the wood has to be completely dry otherwise you will trap moisture into the tree and then it will be destroyed.

On the base ring I put 20 small wheels and a strip of styrene foam (5*5 cm) was glued to the ring.

This foam was glued in place with the same glue I used to the dome it’s special contact glue made by Bostic.

The reason that I put the strip there was because this is a point where the wind will have plenty of room to venture inside your dome even if you have the side skirts on, believe me.

You as well as I will learn by your mistake. But then again there has to be a 5 mm opening still because otherwise the upper ring will get stuck.

The skirts are made of Masonite 10cm wide (to cower the upper ring, opening and go below the base ring 1 cm), this is very important because otherwise the rain will be able to get through in stormy weather.

With this mounted I painted it with epoxy plastic (but any 2 component boat paint will do fine)

Then there has to be a skirt on the inside but this is not to be as wide as the outer but 6.5 cm will be enough, this is to prevent the wind from the 5 mm gap to get into the dome and to prevent people’s fingers to get stuck in the wheels.

Now the base structure was snow, water and windproof.

This completed the base construction all that was left was to paint it

The most important aspect of the dome is to make it watertight and durable so that it won’t fall apart after two or three years

If it is not watertight the Styrofoam will eventually soak up water, if it is not protected.

So I looked around for different solutions.

First I put on 4 layers of newspaper and diluted wooden glue. 4 layers went on to give it a smooth surface.

After this was dry I put on a grassfire net and lamination epoxy NM 456.

This product is exceptionally well suited for the job and went on without problems. This epoxy is produced here in Sweden by a company called Nils Malmgren AB and is the best material I used for this project, for information see my links page.

Within 24 hours I put on 2 extra layers making it a total thickness over 4 mm this in combination with the glass fiber made the dome into a totally watertight boat hull.

But then there was the problem with the weight, it was to light and a gust of wind would easily throw it into my Nabors garden.

So I went along with Joe’s idea of putting a layer of stucco on top of it but with one or two minor modifications.

First I used ultra-fine quarts sand and a component called fugolastic to make it both smooth and elastic to avoid cracks, onto these 2 layers of siliqua paint was applied, that’s it! I thought.

The same winter it seemed that the stucco was put to the test with the result of small cracks (on the perimeter seal ring only).

So I decided to play it safe and applied 2 layers of epoxy on top of it followed by 2 layers of 2 component boat paint.

And now there is no problem even with the perimeter seal, this part is by the way the most difficult part of the whole dome, see my construction page why.

With the dome done I turned to the woodwork, this has to be secured to if it is to stand rain or snow.

First I put on a layer of paint then a layer of epoxy sealing the wood and paintwork and making it a perfect painted surface.

And voila! The dome won’t get wet and the stucco prevents it from visiting my neighbors it also became so sturdy that my kids can stand on top of it without any risk of breaking it.

The main part of my observatory is of course the telescope itself.

To have a sturdy mount not sensitive to vibrations is essential, so how did I solve this problem?

Telescope pier

First at the place where I should have my dome I dug a hole in the ground 60 cm deep.

In this hole I put a flagpole base mount and filled the hole with concrete.

It is a very good idea to do it this way because the flagpole mount allows you to adjust the pole if the ground sets after winter.

Then I went to a company that makes flagpoles called Formenta, here where I live and for less than 20 $ bought the bottom part of a flagpole (this is the part that is casted into the flagpole during construction, it is of galvanized metal and therefore it is not only sturdy but also it doesn’t rust)

This part has tree adjusting holes to fit the adaptor in the ground.

When this was finished I turned to the mounting of the scope itself.

As I am on a low budget I opted to use an old mead star finder mount that was lying around and together with one aluminum adaptor ring turned in my lathe it fitted perfect.

I then filled the tube with concrete to make it even sturdier.

So much for the pier, but then I realized a problem after having constructed the base I found that air venturing in under the floor was compressed by the shape of the floor itself (it looks like a bit of a cake)

This fact pressed the air up inside the dome with tremendous force even after the insulation plate was mounted making the mount wet of incoming moisture.

I therefore removed the insulation plate and the pier ( by now really heavy) and took a piece of butyl rubber canvas, for making ponds and made tree small holes for the flagpole bolts , repositioned the pier and stapled the canvas on the underside of the floor thereby stopping all draft and subsequently no more moisture.

 So now you can go about and make your own observatory , if you have any questions, dont hesetate to let me know.