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New build observatory.


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Hi all.

Will be building a new block observatory in a elevated coastal location in NW Ireland. Very good dark sky conditions. Structure needs to be solid to avoid potential storm damage. Before joining Stargazer lounge had worked out that my best option was a slightly pitched flat roof with a sliding hatch. Have since seen Sandancer10 using a similar set up for roof access with a Surespan sliding access hatch.. A roll off roof is not possible given potential storm damage or weather ingress.

View will be very full if structure built on a two story small hut basis.

I have a Celestron CGE Pro with an Edge 11" HD tube. The setup will be on the upper level.

If I do not construct a concrete pier which would be from ground level and around 10 feet+ high I envisage using precast concrete floor slabs to place my CGE Pro tripod on. Ultimately to allow access to low horizon I would consider a tripod based elevating pier. To use a Pier Tech 2 or a Polaris precision pier would require anchor bolts in the precast floor but I think this would potentially cause damage to "hollow" precast nature of these slabs let alone hoping that an anchor bolt would not be through into one of the airfilled slab sections. These slabs would have to be bespoke cast given their shorter lengths and thus I could discuss any potential anchoring requirment with the supplier.

My big big question is would this very solid floor choice be adequate for astrophotography or would floor vibration be too great or should I go the long concrete pier route.

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Not an answer to your main question. But a comment your roof plan.

I have a full size sliding roof, not a hatch.

On 3 sides, the roof extends down below the walls, keeping out the weather.

On the 4th side, there is a hinged flap. When the roof is closed, the hinge is down, keeping out the weather.

When the roof is opened, the flap lifts up, on a couple of castors.

The roof material, including the hinged area,  is butyl rubber pond liner.

More expensive than roofing felt. But it is holding up well against time, weather and lots of open/close operations.

To keep the roof in place when closed, there are metal pins, 8mm dia that push into sockets firmly fastened to the upper part of two walls.

These ensure the roof will not lift in a strong wind - or if a thief calls.

The pins & sockets are on the travel direction walls, so engage/disengage automatically when the roof is slid.

Motive power very quickly moved on from 'heave and grunt' to a garage door opener with minor adaptation.

There are lots of 'shed' discussion threads on SGL. If you can get a look at a few before starting your build, it will be a great help.

Even better would an eyeball on a couple of home built obsys, if you can do this.

Hope this helps.

Edited by DavidValentine
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I have a 20 feet high 1 metre square block built pillar supporting a large mount carrying a 16" SCT with no apparent stability issues. A blockwork walled observatory would need double skinning or tanking to stop rain permeating in high wind. :smiley:

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I don't think using precast floor slabs would be a good idea. There would be too much 'bounce' which would be transferred to the pier.

Your pier needs to be built up from the ground on a solid foundation with the floor isolated from the pier to stop transmitting any vibrations to the pier.

What I mean by bounce is that pre cast concrete is inherently springy due to the fact that that the beams have tensioned steel tendons which are released when the concrete is cured causing the beams to arch upward slightly "hogging" so when loaded they resume a flatter aspect but this makes them springy.

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