10" Portable Truss Dob for Skywatcher mirror set

[Gonzo]

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.

I need to search fleebay for a used 10" or 12" scope.

[Naemeth]

I need to search fleebay for a used 10" or 12" scope.

http://www.ebay.co.uk/itm/Sky-Watcher-Explorer-300PDS-12-Newtonian-Reflector-Telescope-OTA-/160944037158?pt=UK_Photography_Telescopes&hash=item2579031d26

[Moonshane]

as promised, here's some more pics.

the first two show the scope built for transport. the bolts locking the rocker box and the mirror box together are the same as those holding the side bearings on. the beans are just for scale of course but can be used as a counterweight or used to generate methane based tracking - this takes some skill though (joke).

Here's the detail on the corner/fixing point of the lid

the primary in situ

the lid acts in a dual function as a mirror protector while setting up. it can be removed once the trusses are all fitted.

here's the scope with alt bearings fixed. the proximity of the camera makes this look bigger than it is.

[Gonzo]

http://www.ebay.co.u...=item2579031d26

saw that one earlier thanks, it's a bit on the high price for my budget dob I'll wait until I see a bargain.

[Beulah]

Shane,

Is it possible that you could draw out some plans for this please? I for one would love to have a copy.

[Astrobits]

A very nice looking job there Moonshane. I have only used the Polyx Oil for my floor so far but does go on easily and dries hard.

Hope you checked that you will be able to remove the mirror cover after assembly.

I made 16" truss dobs similar to your design which have worked very well. This one won a prize at a telescope making event in Johannesburg in 2010.

The 16" mirror is held onto a MDF disc with three blobs of Silicone about 1 1/2" -2"dia and 1/8" thick only.

The top tube was made by an air-conditioning/fume extraction business to my spec. The woodwork is all MDF ( It's called Supawood in South Africa, we didn't have the same choice of materials as in the U.K. )

The truss tubes normally live in a denim pocket that ties to the alt bearings so they don't fall out. I made them from Aluminium tubes and painted with an anti-rusting primer which was a nice matte finish.

The focusser is a 2" crayford type designed and made by me with a two speed knob.

This telescope survived regular trips up a bumpy path to my observing site, a 1200Km round trip to the Telescope making event and shipping back here earlier this year!

Nigel

[Beulah]

That's a great design Nigel.

I would absolutely love to be able to build a large Dobsonian that can be carried on the back. (truss poles carried by hand) The localised LP is pretty bad round my way but a few miles down the road and its a different story. Park the car up and walk to the spot that cannot be accessed with four wheels...

[swamp thing]

Coming on very nicely indeed Shane, lovely bit of timber that. It'll be a stonking good scope me thinks

[Astrobits]

That's a great design Nigel.

I would absolutely love to be able to build a large Dobsonian that can be carried on the back. (truss poles carried by hand) The localised LP is pretty bad round my way but a few miles down the road and its a different story. Park the car up and walk to the spot that cannot be accessed with four wheels...

Hmmm.

At approx 45Kg mine might be a bit heavy on the back.

Might be interesting to see the largest telescope that was still backpackable.

Nigel

[Qualia]

Mind blowing stuff, Shane. You have yourself a well deserved rest and a jolly good Christmas, mate

Feliz Navidad, Shane

[Moonshane]

cheers Rob - already on the mince pies!

[Moonshane]

A very nice looking job there Moonshane. I have only used the Polyx Oil for my floor so far but does go on easily and dries hard.

Hope you checked that you will be able to remove the mirror cover after assembly.

I made 16" truss dobs similar to your design which have worked very well. This one won a prize at a telescope making event in Johannesburg in 2010.

The 16" mirror is held onto a MDF disc with three blobs of Silicone about 1 1/2" -2"dia and 1/8" thick only.

The top tube was made by an air-conditioning/fume extraction business to my spec. The woodwork is all MDF ( It's called Supawood in South Africa, we didn't have the same choice of materials as in the U.K. )

The truss tubes normally live in a denim pocket that ties to the alt bearings so they don't fall out. I made them from Aluminium tubes and painted with an anti-rusting primer which was a nice matte finish.

The focusser is a 2" crayford type designed and made by me with a two speed knob.

This telescope survived regular trips up a bumpy path to my observing site, a 1200Km round trip to the Telescope making event and shipping back here earlier this year!

Nigel

superb scope Nigel. I suspect that the drier (presumably??) conditions in South Africa would make this an ideal material. the cover was made to be the right size to be extracted from the mirror box once built. obviously the final test comes when the trusses are cut and the bottom holes drilled but anything's solvable.

[Moonshane]

Coming on very nicely indeed Shane, lovely bit of timber that. It'll be a stonking good scope me thinks

cheers Steve

how are you getting on with yours, the link never seems to pop up with updates these days.

[Moonshane]

Shane,

Is it possible that you could draw out some plans for this please? I for one would love to have a copy.

hi Sam

I don't really 'do' plans as such (maybe I should start as it would make future builds easier - probably) but work using Kriege and Berry plus the dimensions off each mirror set/cell/spider. I am not sure I have the skills to do a good job of a formal plan.

[Moonshane]

Coming on very nicely indeed Shane, lovely bit of timber that. It'll be a stonking good scope me thinks

by the way Steve, one thing about birch ply as you probably know is that compared with the average hardwood ply, it's quite heavy and also like iron to machine and drill. superbly strong, rigid and solid though.

[swamp thing]

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cheers Steve

how are you getting on with yours, the link never seems to pop up with updates these days.

I'm still waiting on parts (alt bearings that got lost) starting to get really fed up with it though.

I should have finished months ago and would have if they'd got here.

[Moonshane]

blimey, you must be fuming. will be worth it in the end as they do look superb.

[Astrobits]

superb scope Nigel. I suspect that the drier (presumably??) conditions in South Africa would make this an ideal material. the cover was made to be the right size to be extracted from the mirror box once built. obviously the final test comes when the trusses are cut and the bottom holes drilled but anything's solvable.

Unfortunately not where I lived near the east coast. Sub-tropical, usually warm and humid. Nice during the day and the clouds collected in the afternoon in spring and summer. The last year that I was there the cloudy time started in September and I got 3 or 4 evenings clear by the time I packed up in April. My last recorded observation was in the first week of October!.

Winter was the observing season but then it was very dry from April/May to the rains in August/September. The land dried and grass fires were frequent, not to mention the habit of the sugarcane farmers burning their crop before harvesting. As winter went on the skies became thicker with dust and smoke and really messed up the seeing.

Choice of materials was very limited. It was MDF or very poor quality ply. As I have the tools and the plans, making another one is not a daunting task. However, I have devised a method of making MDF virtually waterproof but I have not applied it to this build.

I mentioned the mirror cover as when I made my first one to this design I took it to an exhibition and used a piece of clear perspex just fitting in the mirror box so that the mirror could be seen but no grubby little fingers would get near the surface. I then realised that I couldn't remove the perspex while the 'scope was assembled. Fortunately it wasn't necessary to remove it at the time. After that I made a tight fitting cover before finishing the mirror.

Nigel

[Moonshane]

sounds like a very interesting place to live !

I did have to shave a few mm off the ends and bevel the edge slightly to make sure it was easily removed but it's straightforward now :0)

[Carbon]

Wow, that's coming along nicely Shane!

I know exactly where you're coming from as far as plans go. I usually make quick, rough sketches, study them for a while, make changes, if any, and begin construction. I continually make minor design and measurement changes as I go to, so there's really nothing concrete drawn on paper (or napkins). I basically like to "visualize" every step as I go. )

[Beulah]

by the way Steve, one thing about birch ply as you probably know is that compared with the average hardwood ply, it's quite heavy and also like iron to machine and drill. superbly strong, rigid and solid though.

I'll back this one up - I have made a dob secondary, mirror & rocking box out of bog standard DIY ply and although I feel it is strong enough to withstand use, birch ply is strongly recommended for this type of project. Using standard ply can be a magical mystery tour with all the voids that suddenly appear where you don't want them.

[Qualia]

Just read this thread through again and this is really amazing work, Shane. A big salute to you

[Gonzo]

I shall make a trip to Wickes this week-end....

[Moonshane]

made good progress last couple of weekends but not as much as I'd hoped. that said, almost ready for the finish. I'd sooner take my time than rush it and mess things up at this stage!

added the bearings and trimmed them/sanded the ultra sharp laminate edges etc and out it all together (other than mirrors) to see how it all fits. set up is quick - < 10 minutes and it all fits very well. I made the truss tubes so that they all stay together as one unit and undo like a concertina.

it looks good and with no mirrors in the balance is spot on. I am sure that things added at the top end (finders, secondary, eyepiece) and the mirrors at the bottom end will all ensure that balance is maintained at all elevations and when the eyepiece is removed to change. if anything it will be bottom heavy and this is easier to correct with e.g. a couple of spare batteries in the telrad.

next decision is the finish as I bought a tint called Terra which in the pics looked like a brownish red. on opening the tin it looked a lot darker (like soil color - should have know I suppose from the name!). that said it has dried a quite nice walnut colour on my test piece - ALWAYS DO A TEST PIECE - so I think it might actually be rather nice and a bit different. I'll make a decision shortly.

here's some pics which are next to a standard garden chair. I could reach the eyepiece at the zenith and at the horizon with ease from this chair.

[nightfisher]

Shane, that is really coming on leaps and bounds now, and i have to say even though its a mirror thingy, its looking good, is the mirror set OO 1/8