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If you don't/can't/won't dig a BIG (pillar) hole


Macavity
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Some folk might be (as I was!) put off the idea of beginning an observatory, with the thought of the initial "dig" re. the pillar. Those interested in visual astronomy or casual(!) imaging may have less to fear. :o

As an existing owner of a (rather nifty!) Skywatcher pillar, I just sawed holes through the chip-board observatory base, allowing THREE 2x2 (4-brick high) concrete brick pillars (plinths?) to be built onto the underlying 3'x2' slabs. In fairness the slabs were WELL bedded on concrete, laid over previous, settled hardcore. The SW pillar sits atop the bricks.

RESULT : While monitoring the image via Videocam - approx. equivalent to a 10mm eyepiece, you can SEE the effects of a (rather chunky) me, *jumping* up and down. But these damp quickly! Normal (quiet, night) walking around is undetectable. Individual VIDEO frames (upto 10s real time) are unaffected. :o

With experience, I'd've preferred the scope mounted 6-12" further to the SOUTH. LOL. I'm not sure how to break this to my tame-brickie friend, who carefully crafted the very SOLID mini-pillars! Now with more confidence, there is even the notion of "retrofitting" a central pillar? Dunno if anyone has ever been THAT adventurous (or unwise!) though... ;)

P.S. NOT to dissuade folk from doing a "proper" job - Especially where serious imaging is envisaged. But simply to remove an initial (physical, mental?) obstacle re. starting the project! :D

Edited by Macavity
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TBH a lot of people read far too many American forums where they seem to not settle for anything less than a nuclear bunker bolted on to the end of the pier. If you have a clay subsoil a 2 foot x 2 foot cube will suffice for your average EQ6 mount, if there's an observatory sitting over the top of it frost creep will not be a problem in the UK so you don't have togo deeper or wider with the hole.

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Before starting my 'dig' I looked around for definitive information on stability/depth and conldn't find anything relevant. Also I did not know what type of scope I might have in a few years. Having no building knowledge of my own to fall back on, I just did what I thought best.

So I thought a little about the consequences of getting it wrong.

If I got it too small/shallow, I would have to remove the shed, dig out the concrete shed base, dig out the existing foundation, etc, etc. A lot of hours and lots of £££££.

If I got it too big/deep, it was more spadework and another couple of barrowloads of concrete to be mixed. A few hours and a few ££.

So I went for 1 metre deep hole, about 80 cm wide over most of the depth. Tapering near the top into a 30cm round steel tube for the pillar. This being a piece of spiral ventilation duct placed then filled with concrete. The whole lot was filled in one session to avoid joints.

Over the top on size & depth? Probably.

Risk of having to do it again? Near enough zero.

David.

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We are temporary exiles in Europe and renting property doesn't allow you to dig big hole's in the back yard!

I've relocated the Argos TSO (Tin Shed Observatory) from the UK and set it up on a compressed path area. The NEQ6 tripod has to sit through the rubber flooring straight onto the gravel...that's as good as it gets.

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If you have a clay subsoil a 2 foot x 2 foot cube will suffice for your average EQ6 mount...
Hmmm. My mate - a landscape gardener, ALSO kindly dug ten massive holes, over two evenings, for concrete fence posts etc. Embarrassingly, for (frankly) "Beer money" too. What can I say - A good bloke! :eek:

As it happened, it wasn't "too bad" (his words!) getting as far as clay / rock, a couple of feet down. At the time, I didn't like to ask for a "mini swimming pool". In retrospect, a shame... If only I'd thought. ;)

Edited by Macavity
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If its any help. . . .

I recently installed a new dovecote in our garden. The thing is 12 feet tall overall with 3 feet of the 6 x 6 inch pole underground. Total weight of dovecote and pole is 55 kg. Hole size is 3 x 2 x 2 feet.

Obviously its all wood but very heavy and the amount of movement at the top is tiny.

So similar mass and you should be good

Cheers

Ian

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I bought a cheap (£150 I think) petrol driven borer when we were digging our pond. Joining up the holes and shovelling away the broken up bits was comparitively easy. Our soil is really heavy clay so a pick is generally more use than a spade. Unfortunately I didn't have the borer when digging for the mount. The limit of a borer is the depth of the auger, often 2ft or a bit more, unless you buy an extension.

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