| article: building a small backyard observatory ( appr. € 500,- ) |
Since two years I was planning a small observatory in my backyard.
I studied carefully all the constructions of other amateurs from the book *Small Observatories* and from the Internet.
But I had very limited space of only 2 m to 1.6 m outside measurement of the hut.
So I was not able to realize my favourite - the roll-off roof.
I came to the conclusion that my best option would be something like a roof of two parts which I could open up with joints.
I planned the two parts of the roof in asymetric way.
The south side is 1.4 m while the north side is only 1 m.
Hence, when I open the more important south side I can reach the zenith as well.
The height of the walls is a bit more than 1.4 m so the opened south part of the roof could clear the ground.
I constructed everything around a framework based on single concrete foundations with steel fastening for the framework.
We have very strong winds here, so I took 70 mm square timbers.
The frame was filled with wooden panelling.
This was an easy task for the rectangle parts but harder in the triangles.
I installed a door from the same wooden panelling mounted on a 10 mm wooden board.
The roof was made of the same 10 mm board.
To the outside there is a rigid plastic film which is used for tents.
To the inside there are 24 mm strips of wood to give a leightweight construction.
I strengthened it with 90 degree mountings made from steel and screwed everything to the board.
The two parts of the roof are mounted with 4 joints each placed in equal distances.
The joints are heavy duty versions of what you can use for furniture doors.
When the roof is closed the south part is overlapping the north part.
The film is overlapping too, making the whole construction water proof without relying on a rubber sealing only.
There is a rubber sealing too but more to be on the safe side if a heavy wind is blowing while it's raining.
When the roof is closed there is a locking mechanism - again because of heavy winds and somehow against thiefs too.
Each part has one lock on every side.
This lock is normally used for furnitures like chests.
I found out that with the roofs locked the whole construction gains more rigidity as well.
The peer for the mounting is 1.1 m high and has a diameter of 125 mm.
This turned out to be rock solid.
It is screwed on a separate concrete foundation of 45 x 45 x 80 cm to be well below the frost.
The wooden floor is placed on timbers and is not touching the peer.
So I can even jump on the floor and will never notice vibrations to the scope at all.
I installed a little table for the laptop and a mini seat.
As you can see the space is just enough to clear the 10 inch f/4 newton telescope.
Because of the walls and the height of the peer I can only go down to appr. 20 degrees above horizon.
I would like to have 10 degrees now.
The peer should be something like 10 cm higher.
But on the other hand are the trees around still growing and would block the sight anyway sooner or later.
So I am rather satisfied.
After finishing everything I experienced dew condensating well after sunrise on the mounting and on the mirror.
So I installed two little ventilation openings.
One on the top right under the roof (see above) and the other near the ground.
It looks like this has solved the problem.
Conclusion
The overall performance of this type of observatory is fine.
Having a permanent installed scope is a huge advantage when it comes to deep-sky imaging.
pros:
- Takes minimum space
- Cheap parts can be used
- Fast setup for the main observation directions (around south and zenith)
- Shields scope quite well against dew
- Shields observer well from cold wind and hungry insects
- Rigid construction for windy places
- No dome seeing or need to move a dome-slit
- Absolutely water proof
- Almost no noise when opened or closed
- Permanent power available, no need for battery recharging
cons:
- South part of the roof is hard to open for a single person (heavy!)
- Limited view to east and west for low altitudes
- Telescope clearance to the walls must be planned carefully
- Upgrading to a bigger scope might be a problem (at least if it is a Newton again)
30.04.03 Housing a 12 inch f/4 Newtonian
My observatory is now housing the NVLT, a 12 inch f/4 Newtonian telesopce.
This is the ultimate limit for that small observatory.
When the telescope is in parking position it is just fitting into the shag.
The huge tube diameter is causing problems for low altitudes of about 20 degrees above the horizon because it is touching the southern wall.
The NVLT tracking the skies.
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