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JamesF

JamesF's observatory build

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Good luck.  That's the sort of problem I have!!

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Good that you spotted it before cutting precious timber. I've certainly done the same and it's really frustrating when your plan goes out the window. Good luck for tomorrow :) 

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7 minutes ago, Astrokev said:

Good that you spotted it before cutting precious timber. I've certainly done the same and it's really frustrating when your plan goes out the window. Good luck for tomorrow :) 

With caution appropriate to the season, I made my list (of measurements) and checked it twice :D

Should be able to do a better job tomorrow, though I think I'm going to have other things to do tomorrow night, so it might have to wait until Thursday, though that's hardly a big deal.

James

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On 11/12/2018 at 13:57, sloz1664 said:

You must have shares in tool station / screwfix. I haven't seen that many clamps for a while. What would you call a "gathering of clamps"

 

A "gripfest"?

 

Hey, if, collectively, we all start using the term, it could be in the OED by the end of next year :)

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53 minutes ago, iapa said:
On 11/12/2018 at 13:57, sloz1664 said:

You must have shares in tool station / screwfix. I haven't seen that many clamps for a while. What would you call a "gathering of clamps"

 

A "gripfest"?

An industrial silage unit?

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3 hours ago, Stub Mandrel said:

An industrial silage unit?

:D

Don't know how many people still use silage clamps these days.  Around here it's far more common to bale silage now.

I managed to get out today and re-measure the northern gable.  I even used a few more clamps to fix bits of timber into place to make the measurements more accurate :)  This time my measurements come to within a couple of millimetres of the southern gable, so I've no idea what happened first time around.  Gravitational wave distorting my tape measure, perhaps.  I'm quite pleased to be so close having welded up a structure of that size.

Anyhow, having confidence that I had things right this time I managed to get out this evening and cut the OSB to fit.  I'd best have it right, because I've used about 20sqm of OSB in total and there's probably not even 1sqm left over now, all in small bits.

I've decided to try to avoid climbing onto the warm room roof to do most of the fitting.  I reckon if I open the roof about 1/3rd of the way then I can hold the OSB in position and fix most of it from a ladder propped against the end wall of the warm room.  If I struggle to reach the ridge then I'll push it closed and just do the last few screws from the warm room roof.  Saturday isn't looking too clever at the moment weather-wise (again) unless I can get up and out there at the crack of dawn, which really isn't me.  On the plus side, the rain all appears to be coming in on southerly winds, so if I can't get the membrane on until Sunday the OSB should still stay dry.

James

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Ugh.  In the last few hours the forecast has changed to a "yellow rain warning" from before sunrise to after sunset tomorrow.  It seems likely that I shall not be working outside :(

James

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1 minute ago, JamesF said:

Ugh.  In the last few hours the forecast has changed to a "yellow rain warning" from before sunrise to after sunset tomorrow.  It seems likely that I shall not be working outside :(

James

 Tough luck, James! The rest of us are enjoying the clear evenings your observatory build has brought us  ?

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Speak for yourself, it was supposed to be clear, but now, there's loads of high cloud, obscuring everything ?

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1 hour ago, Stub Mandrel said:

 Tough luck, James! The rest of us are enjoying the clear evenings your observatory build has brought us  ?

Really???  It's cloudy here...  It's getting ready for the rain...

Edited by Gina

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Darn. Set up under clear skies to take 30s shots for geminids. 400 frames later mostly pictures of cloud, but I think a couple of meteors.

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Well, the rain is now lashing down here.  Not entirely desirable given that in half an hour I'm supposed to be going to pick up an electric piano for my son (seemed like a fair exchange to me :D

On the way back I shall stop off at one of the DIY sheds and pick up the additional bits of plastic piping and fittings that I need to make the ducting under the floor for the cabling to each pier.  I'm going to use a couple of runs of "inch and three quarters" (43mm, I think) waste pipe to each and put the data cables in one and mains in the other.

I've not decided about running a 12V supply to each pier yet, but I might just drop the cabling in and if I don't use it then I don't use it.  Need to have another read of Kev's electrics thread.  I recall someone posting there about suitable cabling for a 12V supply.

James

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I used low voltage (24v rated), high current (16.5A) cable I got from Amazon (I think) for my observatory power.  Separate mount and camera lines.
eg. *16.5 AMP Rated* 1mm2 Thin Wall 2 Twin Core Cable Wire Car LED Lights but I think I bought it by the metre.

You can get low voltage cable in higher current ratings too - useful if you have long runs to reduce voltage drop.

 

 

Edited by Gina

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It did occur to me to investigate running normal mains cable for a 12V supply.  Not sure off the top of my head what the rating is for 2.5mm twin & earth, but I think it's somewhere around 16A @ 240V.

I had to visit two DIY sheds to find my pipe.  B&Q didn't have anything the right size.  Wickes did, but some of it was mislabelled as a smaller size.  It took a while to sort out everything I needed :(

James

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2 hours ago, JamesF said:

Not sure off the top of my head what the rating is for 2.5mm twin & earth, but I think it's somewhere around 16A @ 240V.

  Current rating (as James is most likely aware) is a function of cable length, whereas voltage rating is determined by insulation material and thickness. Here in the US, 15 A circuits are generally wired using 14 gauge wire, while 12 gauge wire is used for 20 A circuits in residential applications. That's a relatively useful guide, but assumes wire lengths typically found in single family housing. A competent electrician will use larger wire to supply outlets at the far end of a McMansion. Cables for dew heaters, thermoelectric coolers, telescope drives and any other high current (whether continuous or surge) applications requires some forethought. It's never a bad idea to measure the voltage at the load end under operating conditions after (or even before) pulling a new cable if there's any question about series drops.

  As for conduits supplying the piers, my experience suggests making them plenty large and leaving a pull string in place. In the three years I had my last observatory, I changed wiring configurations at least half a dozen times as I added and replaced equipment. I supplied only low voltage to the pier, so I eventually needed separate 16 V, 12 V and 5 V runs in addition to a couple of separate USB links, Gb ethernet and one or two dedicated control/status cables. My conduit was about 60 mm ID, which was plenty for the cables themselves, but pulling the last few cables with connectors attached through the elbows was a bit of a challenge.

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I think I shall pass on the idea of using domestic solid core cable for the 12V supply.  It looks like stranded twin-core cables would be more sensible and indeed cheaper.  I've deliberately chosen "slow" elbows where I'll need them in an attempt to make cables easier to pull through.  I was going to buy some string for drawstrings today, but forgot :(

James

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I would suggest going larger rather than smaller. If I could redo mine I would actually use svp, my current pipework is just way to small to take any more cable.

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Yet another grim day here, but I decided I'd get on with the final gable end despite the gloom.  I was a little over half done when the rain started, but by that time I was determined to finish regardless.  I managed to get the roof rolled back into the closed position having completed everything about five minutes before the rain became torrential.

I've even managed to find a temporary door (kind of :)  It should least serve to keep the rain out for the time being.

It's hard to believe, but this photo was actually taken well before sunset.

obsy-build-57.jpg

James

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Yes, it was very dark in that torrential rain - had to put the lights on to see to do my project - Giant 3D printer upgrade.

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I got a little done today -- basically just trying to get through the things that need to be done before the flooring can go down.  It had been my intention to get some of the cladding on, but contrary to the forecast there has been persistent drizzle all day.  In the main scope area I just need the lower block of the piers in place and the ducting for the cables.  I liberally applied "gorilla glue" to the concrete blocks for the piers and then bolted them down to the studding embedded in the concrete using large washers and nyloc nuts.  It was quite a fiddly and time-consuming job because of the limited room for using a spanner or socket wrench.  I'm sure my knuckles will recover soon.  The blocks feel very sturdy which is pleasing, though there's another one and a half blocks to go on top of each pier yet.

I only managed to get the first two ducting runs roughly into place before it became too dark to work.  My plan is to glue the elbows on at each end, but leave the vertical sections loose for the time being, so they can be removed whilst I test the flooring sheets for fit.  Then I'll glue them into place before laying the floor down permanently.

The forecast is pretty grim for tomorrow and not wonderful on Monday either, so doing anything outside might have to wait a while.

James

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you'll be one of the few who will be happy the nights are getting shorter 

 

lol

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39 minutes ago, iapa said:

you'll be one of the few who will be happy the nights are getting shorter

It is a genuine dilemma, to be honest.  I spend much of my non-work time outdoors, so when there's so little daylight and the weather is as bad as it has been for the last few weeks, preventing any chance of getting out with a telescope, I do get quite frustrated.

James

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