10" Portable Truss Dob for Skywatcher mirror set

[catman161]

This looks fantastic. I am amazed every time I read about people's projects at the skills of people out there. I am terrible at DIY and wish I had the skills to work with wood.

Skywatcher Skyliner 200p Dobsonian

Celestron Skymaster 15x70 Binoculars

Sent from my iPhone using Tapatalk

[Moonshane]

I apply with a good quality brush, you only need a small amount because its coverage is excellent. I suppose you could wipe excess with a cloth but it goes on so easily you shouldn't need to. I'm not sure I understand shedding? It dosn't peel if that's what you mean, it deforms with the wood if you bang or knock it.

Another alternative would be Tung oil, 3 coats will give you enough protection. You can literally slap it on and wait 5-10 minutes then wipe off the excess. Easily touched up when you clout it on the door jamb.

Gary.

cheers Gary

I was just referring to the fact that it's a wax and waxes and optics not mixing well. it sounds from reading up though that once it's on it goes rock hard and stays put so it will be fine after application and a buff. also makes touch up in the event of a bump much easier compared with paint/varnish.

I think this will be my finishing medium. might try one coat of the tinted one and one of the clear as I am after a little colour but not a dark oak type of tint. the Terra one looks nice.

[Moonshane]

This looks fantastic. I am amazed every time I read about people's projects at the skills of people out there. I am terrible at DIY and wish I had the skills to work with wood.

Skywatcher Skyliner 200p Dobsonian

Celestron Skymaster 15x70 Binoculars

Sent from my iPhone using Tapatalk

it's all about the tools really. I am lucky enough to have a father in law with a full workshop of expensive tools (although I have a router, jigsaw, pillar drill and the usual hand tools) who helps me with method sometimes too. you can do a very good job though with more basic tools and methods if you take your time.

[catman161]

it's all about the tools really. I am lucky enough to have a father in law with a full workshop of expensive tools (although I have a router, jigsaw, pillar drill and the usual hand tools) who helps me with method sometimes too. you can do a very good job though with more basic tools and methods if you take your time.

That sounds like a fantastic workshop. You're very lucky to have access to that. I think aswell experience in working with whatever materials you're using is a huge factor. I have never really tried so shouldn't complain really I guess I should give these things a go more often. You're project is certainly inspiring

Skywatcher Skyliner 200p Dobsonian

Celestron Skymaster 15x70 Binoculars

Sent from my iPhone using Tapatalk

[Moonshane]

you are quite right actually. each project I take on means that I have more experience and learn from the mistakes along the way.. although painted exterior hardwood ply is adequate enough, having used birch ply, I will never use anything else again even if the finished product will be painted. it's superb.

an example is the recent change of the secondary cage struts to plywood. it took me ages to do the ali ones as I had to do a lot of metalwork. the ply ones were a lot quicker and to my eyes are more aesthetically pleasing. I'll be using ply for these on any future projects.

[Moonshane]

I apply with a good quality brush, you only need a small amount because its coverage is excellent. I suppose you could wipe excess with a cloth but it goes on so easily you shouldn't need to. I'm not sure I understand shedding? It dosn't peel if that's what you mean, it deforms with the wood if you bang or knock it.

Another alternative would be Tung oil, 3 coats will give you enough protection. You can literally slap it on and wait 5-10 minutes then wipe off the excess. Easily touched up when you clout it on the door jamb.

Gary.

well I bit the bullet - like the look of these oils, seem a lot less messy than varnish. I ordered a black stain for the inside of the mirror box (and possibly the rocker box too) http://www.wood-finishes-direct.com/popupcolours.php?pid=8ℑ=black-ws#black-ws

I'll do that first and then apply a clear matt Osmo Polyx and then a coat of the 'Terra' Osmo Polyx tint everywhere other than where black. http://www.wood-finishes-direct.com/popupcolours.php?pid=174ℑ=osmo-colour-foundation-terra#osmo-colour-foundation-terra

finally a further coat everywhere of Osmo Polyx clear matt (maybe two).

[8kids]

Now I come to think of it I didn't mean Osmo polyx oil...... ....Only kidding, it's a great product.

Gary.

[swamp thing]

Hi Shane

Most exterior treatments work well for plywoods just make sure plenty of it soaks into any exposed end grain as this is where most water ingress will occur. I varnished my UTA before assembly to make doubly sure there is no exposed areas for water to get in. Light sanding with a finishing paper between coats helps to get a lovely deep smooth finish.

Did you decide against the biscuit joints on the focuser and finder boards?

[Moonshane]

cheers Steve - one good thing about the ply I am using is that it fine sands to a very hard and smooth finish on the end grain. hopefully this and the combo of the hard wax oils will help keep out any moisture. I'll be doing each piece individually too for the same reasons.

in the end I went for a removable focuser/finder board as things sometimes change and this will allow the boards to be removed in the future if required for e.g. a different focuser to be fitted and a new drawtube hole to be created in a different size.

it's amazing how easier it is to move about with the hand holes cut out. I planned in advance too, making them big enough for even gloved hands.

[Joseki]

Hi Shane,

this is a great thread and your scope's looking nice. I was wondering, are you working from/adapting plans? More specifically, I'm thinking about getting either (or both) "Engineering, Design and Construction of Portable Newtonian telescopes" or "A Practical Manual for Building Large Aperture Telescopes". Leaning towards the first. - has either been directly useful for this project? thanks

[Moonshane]

Hi Shane,

this is a great thread and your scope's looking nice. I was wondering, are you working from/adapting plans? More specifically, I'm thinking about getting either (or both) "Engineering, Design and Construction of Portable Newtonian telescopes" or "A Practical Manual for Building Large Aperture Telescopes". Leaning towards the first. - has either been directly useful for this project? thanks

I should really draw plans but tend to make every project individual. I find that as I make each scope I learn from the process and change things next time around (or not). Personally I have not seen the former book but the Kriege and Berry book is my mainstay reference and I'd highly recommend it. i also tend to prefer more than one source of reference so online sites like Stellafane and your other suggestion will be on my list shortly.

my personality means that I am always looking for ways to improve things that I do and even though I have made a perfectly functional chair I want to make a better one and I'll also be remaking some of my current solid tube scopes to truss scopes in the future. I may also make another EQP.

[Joseki]

Thanks, I imagine it would be a lot of work producing plans if you don't need them. I guess I want a fancy airplane model without all the effort involved in properly understanding its construction - not a good idea probably (and less fun in the long term).

[Moonshane]

trial and error (and necessity) are the mother of all invention. I like your build thread as it's warts and all. shows your successes and failures and how you overcome them - that's what it's all about. despite what you say, if it works well then you understand the mechanics well enough

[nightfisher]

Seeing how your projects come together, i think if i were ever tempted to get a dob, i would have you build one of these for me!

[Moonshane]

Seeing how your projects come together, i think if i were ever tempted to get a dob, i would have you build one of these for me!

cheers Jules - how kind of you to say so . the ultimate compliment. Jules even remotely considering the purchase of a dob, however tenuously - must be a change of tide!

[nightfisher]

Did not say i was getting one said IF i were to........think i will stick with my refractors for now

[Moonshane]

the dob forces will attract you......THE DOB FORCES WILL ATTRACT YOU........THE DOB FORCES WILL ATTRACT YOU (ETC)

ha ha only joking mate I know you have fracs in your blood.

[Qualia]

Seeing how your projects come together, i think if i were ever tempted to get a dob, i would have you build one of these for me!

Ay, that really is a decent sounding plan.

[Moonshane]

I had another full day on this on Friday and made good progress. Will upload pics in due course but need to take some first!

The following tasks were completed:

• Finished off the side bearings - made these a little wider (18-24mm) so they have a lot less flex. Happier with them now.
  
• Drilled holes in the mirror box for the side bearings. The calculation/guestimate/trial and error for the position (holding with clamps during testing). This is in a position to maintain the mirror box as low as possible to assist the balancing.
  
• Shaped and finished the corner braces for the mirror box / truss pole bottom fixings
  
• Drilled the holes through the mirror box and rocker box to fix the two together during transport
  
• Created a top for the mirror box which also acts as a cover for the primary during build up/break down.
  
• Made a jig for establishing secondary cage height at focal point and allowing measurements of the truss poles (they ended up at 600mm between fixing points so this will be rock solid truss).
  
• Cleaned up all the woodwork in preparation for finishing.
  

Just now need to :

• Glue on the alt and azimuth bearing materials
  
• Drill the truss poles and final trim
  
• Add black heat shrink to the poles
  
• Fit the fan
  
• Make / fit the secondary baffle
  
• Stain the interior of the mirror box black
  
• Treat the timbers with the final finish
  
• Test
  

[8kids]

I was thinking of making a 8" truss dob but I've not located any secondhand mirrors yet, so I'm thinking of changing my 300pds to a truss dob. So I'd like to see your piccys so I can rip off your design.

Gary.

[Moonshane]

one of the reasons I do these threads is to encourage people to have a go as it's a do-able project albeit a lot of work.

I'll be converting my own 12" f4 and 16" f4s into truss formats in the future.

[Gonzo]

Hi Shane,

I'm about to start building a travel truss dob, first dilema... should I buy the mirror now or later on?

[Moonshane]

hi Gonzo

personally I prefer having the mirrors before I start but it's not essential. It does make the positional decisions (e.g. focuser hole etc) easier. the way I normally do things is to buy a used OTA and you then have everything you need.

[Naemeth]

Looking forward to seeing this finished Shane . You have excellent building skills .

[perrin6]

I was thinking of making a 8" truss dob but I've not located any secondhand mirrors yet, so I'm thinking of changing my 300pds to a truss dob. So I'd like to see your piccys so I can rip off your design.

Gary.

Why not try making a mirror yourself - it's easier than you might think (and kind of addictive). I much improved my 350mm mirror without any previous experience.