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10" truss dob build... yep, yet another one!


Andy_E

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Hi Andy

Can you tell me what those mirror support bars are rocking on ? Is it a simple screw into the wood underneath?. I used thick cable grommets as a.support and stiff rubber stick on pads for my12".

Seems.to hold collimation stably.

Cheers

Mike

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Hi Mike. Yes it's just bolts coming up through the wood. I'm attaching three retaining bolts 1" away from each collimation knob... hopefully should aid in holding collimation :tongue:. I'm kind of cheating with the mirror cell; the optics have come off a stripped Skywatcher 250p DS so I figured I may as well 'recycle' the original cell instead of building a new one from scratch.

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Yeah, really looking to the truss trial run... She aint the best looking scope in the world but I confess I'm growing quite fond of her!

Oh I dunno, she looks okay to me. :) they do grow on you when you build them yourself, far more than any bought ones.

Look forward to the truss trial too. It's when things really start to come together. ;)

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I echo Steve's comments - looking good so far! Progress often feels so slow, but an hour here, an hour there and suddenly...*poof*... a component is complete.

I'm looking forward to your truss trial as well.

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Managed the odd bit of work here and there on the scope over the last week. Sorted out the spider support nuts, virtually finished the mirror box and got the UTA ready for a final fix. Can't help but notice that things are grinding to a halt as I wait for parts... Aluminium parts to be precise. Found a nice dark teak woodstain for the ply though which looks pretty good, if a little 1980s! I'm drawn towards square tubing for the poles. might end up a little heavier but like the idea of a clean joint to the truss connectors.

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Very much so. I've only been waiting a week so I can only imagine how you felt! Still, these things are sent to test us, gives me plenty of time to re-design the whole telescope in my head before the next stage!

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Very much so. I've only been waiting a week so I can only imagine how you felt! Still, these things are sent to test us, gives me plenty of time to re-design the whole telescope in my head before the next stage!

Lol..."only a week" feels sooooo much longer though doesn't it! I don't know how Steve remained so calm waiting as long as he did.

Any more pics yet Andy?

Scott

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As promised here's a few pics of the progress. Doesn't feel like much has happened in the last couple of weeks but I guess that's just how it is at 'this' stage.

I've tried to keep the rocker supports quite low to keep size to a minimum. I suspect this will effect the balance somewhat, so I've planned in for a counterweight to even things out (size is more important than weight on this build).

For the spider support bolts I've gone for a hex head instead of the allen key type to enable me to attach some DIY 'bob's knobs' esque handles... trying to make everything as tool-free as possible.

Anyhow, I should hopefully be receiving some parts next week that will allow me to crack on, here's to hoping!

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Looking good there Andy!

Are you going to cut out a hole in the centre of the rocker box to allow the mirror box to rotate through the box flex rocker style, or are you going to adjust your bearing position?

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Hi Scott. I was planning on adjusting the bearing position to get clearance as the mirror box is shallower than it appears on the pictures (it's about 6" deep). However, if this causes serious balance issues I've got about 4" breathing room between the AZ bearings that the box could recess in to a cut out (hope this makes sense, it's hard to explain without pics!). Hopefully the first option should be sufficient with a small counter weight, but it's always good to have a plan B!

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Makes perfect sense to me :smiley:. If you haven't measured/cut your bearings out yet then there should be no problems with clearance or balance once you've determined the CoG. Looking forward to seeing the outcome!

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Thanks to the nice weather I've managed a bit of work on the UTA. All holes drilled and ready to be stained (in fact, the first coat is drying as I type). Quite pleased with how solid it is and everything lines up beautifully. Even though everything was measured, checked, then measured again, it's still a nice sight to look through a sight tune in the EP holder and see a nicely centralised, round secondary... brought a smile to my face so it did!

The truss tubes are to be attached to some alu' angle that will bolt straight on to the UTA. Thought about getting/making an ergonomic [removed word] for the bolt, but there's plenty of room for a wing nut... shouldn't be fiddly and the easiest/cheapest option... both a winner with me!

Really starting to enjoy this now. Things are really coming together and (touch wood) everything seems to be going to plan. Why on earth did I wait this long to build, not had this much fun in ages!!!

PS Scott: the bearings have been cut based on some preliminary calculations, however I have made sure there's plenty of spare wood just in case I was way out! post-23686-0-19942200-1373565553_thumb.jpost-23686-0-21290100-1373565597_thumb.j

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Ah, see the confusion now. The focuser will be at 45 deg, just doesn't look like it in the pic (the spider is at 45 deg too). Still undecided about the baffle material. I must say a couple of the recent builds with aeroplane ply (1.5mm I'm guessing) look really good, but I'm struggling to source anything less than the standard 2440/1220 sheet locally. Out of interest Steve, what thickness plastic sheet did you use and where did you get it from? I'm struggling to find a good source of this too. Cheers, Andy.

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IIRC mine is 0.75mm thick. I got mine from a local plastic supplier.

Try googling "plastic suppliers Cheshire" it would prove much cheaper than buying one from down here and getting it delivered.

Pastic sheet easily rolls up small enough to go in any car, so I would collect it myself.

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Really starting to enjoy this now. Things are really coming together and (touch wood) everything seems to be going to plan. Why on earth did I wait this long to build, not had this much fun in ages!!!

PS Scott: the bearings have been cut based on some preliminary calculations, however I have made sure there's plenty of spare wood just in case I was way out! post-23686-0-19942200-1373565553_thumb.jpost-23686-0-21290100-1373565597_thumb.j

Nice going so far Andy! It's hugely satisfying to see something you planned from scratch coming together....and actually working too :).

Re: bearings. You're all over it. Even if not, experimentation is a huge part of the fun too.

What stain are you using? I used a clear varnish on pine ply which fortunately came out ok, but was undecided about using something just dark enough to obscure some of the blemishes without hiding the wood.

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Cheers Steve, I'll have a check. Thanks for the comment Scott, I've gone for a teak stain to cover up any sins :grin: . After a couple of coats it looks pretty dark but the wood patterning is still coming through nicely... starting to look like a piece of Victorian furniture :eek: . I toyed with the idea of a clear varnish but as it's standard hardwood ply I'm using some of the surface veneers are a bit uneven colour/grain wise. I bet clear on pine looks pretty damn nice!

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Right, time to order some aluminium poles! 3/4" 16swg square box tube is the way forward... quite like the idea of the poles sitting flush to the fixings, plus I'm planning to flock the inside edge of each pole. Some quick calculations suggest that each pole will be roughly 817mm long (giving 20mm above and below each pivot point) meaning I can get away with three 2500mm lengths giving one spare in case of disaster!... here goes....

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