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Horwig

If IKEA made telescopes

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Thanks everybody for the kind words and encouragement. Truth is that not much has been done to the scope since the last posing.

I think I've managed to improve the tilted image plane. It's down to centering of the wynne corrector in the focuser cage, there's quite a lot of adjustment possible.

I'm self employed, and so work comes and goes. My year had been fairly quiet up to the start of September, but then it went mad busy, and the obsy and scope had to ignored.

Trouble is, (apart from the wonderful Welsh weather we've been having) I've started another project, a transportable imaging rig, for more widefield work away from the obsy.

It's an old eq5 I picked up for a song, which works superbly with the Sitech controler I have, and a couple of Pentax 67 lenses for which I've made adaptors.

Suppose I should start a writeup on that as well, lots of small projects involved, and it's starting to produce good results.

I'll get back to the big boy soon, promise!

Huw

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It's been a while, the winter storms were not kind to my dome, if it wasn't for a safety strap that I'd fitted over the shutter, the whole thing would have been flying, one of my neighbours lost part of his slate roof. My weather seal around the upstand under the dome had come away, so gallons of water inside, all so much fun.

Anyway, I've bitten the bullet and bought Maxim DL for image capture and Obsy control, what a revelation, my dome now tracks the scope at last, Lesvedome and Maxim work superbly under Ascom.

Last night  I finally got everythinh in place for a test run at imaging, and here it is, M81 and 82, lots of things wrong, I'm still not really up to speed on Maxim (and lots of other excuses), but I'm fairly pleased with the result.

15 x 200 seconds luminence, and 2x120 seconds RGB.

Huiw

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HI Huw

You've done  a GREAT job here

Can you give me some more details about the fibre glassing and the shutter operation please ?

What were your thoughts about glassing inside and out on the plywood ? Any precautions against on long-term moisture buildup in the wood ?

What plywood did you use ?

How are the shutters mounted ? I see you have a alloy strip retaining one shutter, how does this retract into the upper shutter ?

I have completed a 12" Cassegrain myself recently and it doesn't fit the dome I have so i'll have to raise it - it needed replacing anyway. 

regards

Mike

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Amazing. Im glad i stumbled onto this thread. This is quite a project, great job.

Grwat pictures too.

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Right. In answer to Mike (Skybadger)'s questions in the post above. The dome was made of 12mm exterior ply for the ribs, and 12mm doubled for the main spars either side of the shutter, and the base ring. The gores were ordinary 3mm ply. To give the gores a chance of fixing to the ribs, I first of all glued  and nailed a length of  3mm ply along the ribs to extend the contact surface to a width of about 30mm. The gores were glued and nailed in place, with the joints  being covered in plain weave fabric, and resined in place. The whole dome was given a further coat of resin, and a top coat of Grey topcoat. The inside of the dome was painted with two coats of oil based primer/undercoat. I must point out that this has been my first attempt at fibrglassing since I owned an old mini in my student days, so big thanks to CFS for advise on doing it (http://www.cfsnet.co.uk)

The last winter has been wet (don't we all know it), and some of the gores show signs of mildew on the inside, but nothing too bad, at least the wood can breathe, but I'd be dubious of glassing the inside.

The original shutter was made of wood, and was a disaster. The new one is simpler and lighter, and works. The bottom section is a simple lift off panel, it's only the upper panel that slides. The runners are ali strips screwed into the upright spars, with the sliding panel secured with nylon blocks running under the runners. The bottom panel is secured at the bottom to the dome, and at the top to the upper panel. All fixings to the fibreglass are reinforced with ali panels resined to the outside of the shutter.

I hope the photos explain better than the words.

Huw

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Really enjoyed this tread, an awesome project in which I would not have the knowledge or patience for. I can only image the feeling it must of been to get the first images, and then refining them even further. Thank you for sharing this project, you most certianly deserve a few beers :)

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A quick update on this thread for those thinking of building a wooden dome.

When I originally made the dome, the intention was to cover the ply with woven fibreglass cloth, but my glassing skills were well lacking, with the resin going off before the closh was positioned, so I only covered the joins in cloth, and just covered the rest of the wooden panels in resin and topcoat. The result four years later was that the resin had cracked, allowing water ingress into the ply, and a danger of the dome rotting through.

So back to CFS for some more advice and resin, the old topcoat was abraded with a sanding disk on an angle grinder to provide a key, this time I used Easylam resin, much easier to use than the standard stuff, it gave me sufficient working time to finally cover the panels in cloth, so hopefully the dome will last.

The lesson learnt is that resin on ply DOES NOT WORK

 

The next change will be to the dome drive system, at the moment it relies on friction drive, I'm looking at using a timing belt and pulleys, and I might even push the boat out and motorise the shutter.

As allways, will give an account here

 

Huw

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