10" Portable Truss Dob for Skywatcher mirror set

[Moonshane]

cheers Steve

I agree with large tails and pins and we considered the two boards approach but it seemed much easier to do the rebated butts. might still try it sometime with tails in the future.

[nightfisher]

Looking good Shane, you are truly the dob man

[foundaplanet]

Nice job you have got going on here. Looks like it is going to be quite something.

[nightfisher]

any further progress on this shane?

[Moonshane]

hi mate

other than ordering some bits (metalwork mainly - tubes, ali angle and hardware, fan and a router bit) I have not done any more as I have some heavyweight essay writing to finish before Friday. hopefully this weekend/next weekend will see some further progress and with any luck I'll be in a position to point it at something before final fitting and finishing.

[Moonshane]

hi all

After a week or so off for some college work, I have made some more progress with the build. Fitted the mirror box gussets (add strength and a bit of a shield (plus somewhere to rest the secondary cage on), the mirror cell and made the corner fixings for the truss pole bottom connections. There were in 3mm ali angle and threaded for the M6 countersunk stainless bolts.

Also finished the secondary cage (other than fitting the liner) and tested the position of the secondary mirror - all lines up nicely. Added the truss pole top fixings using a block of 18mm ply plus a M6 threaded insert.

Made the top truss pole triangles to allow two poles to be 'permanently' fixed together to reduce set up time.

Remaining jobs other than finishing are

• to find the correct position for the alt bearings and add three or four balance positions to allow the mirror box to be raised or lowered depending upon the correct balance point.
  
• Fit the bearing surfaces
  
• establish truss pole length and cut the poles (approx 750 mm)
  
• round off /clean up the various bits of metal work
  
• make the ground board and feet
  
• sink in the fan a little to ensure clearance.
  
• make a top
  
• make a truss shroud
  

Here's some pics showing how it all fits together.

[Gonzo]

Very nice work, I'm also planning to build one at some point next year

[Moonshane]

cheers Gonzo - good luck! I am also planning (eventually) to convert my 16" f4 and 12" f4's to this format as it will make life a lot easier at star parties!

[nightfisher]

Converting the 16" would make travel a lot easier for you, would take up much less space in the little hatchback

[Carbon]

That's gonna be a sweet looking set up! Nice...

[Qualia]

Incredibly beautiful work here, Shane. I'm speechless. The attention to detail and craftmanship is perfect and even better when I zoom. Seeing outstanding craftsmanship like this just warms my heart; it is so good to know that there are people of great worth and talent in the world. Thanks for sharing your work and these photos with us, Shane. I salute you

[Moonshane]

cheers guys. looking forward to completing it and getting first light.

[John]

Very nice work Shane

[Moonshane]

cheers John

Not long off finishing now although I really enjoy making them - the first light is always extra special when it's something you have put together yourself.

[Mike73]

Great stuff Shane! Take my hat off to you, I really dont think I would have the patience to build my own.

Whats the plan for the mirror cell?

Looking forward to seeing the 16" build aswell, do you think you will still use your smaller dobs once the big one is finished? I'm holding back on getting another (grab n go) scope until I can justify it, from the little use my 16" has had so far I just dont think I will bother because the ultra compact design means its still very transportable.

[Moonshane]

my 16" is certainly usable in the current format as a solid tube but will be less stressful to transport if truss based. I have a 6" f11 which runs on an EQP and a 12" f4 which will be made into as compact a format as possible as I hope to take this camping etc with the family. there's always room for more scopes, especially when compacted up a bit!

for the scope in question, the mirror cell will be the one with the mirror (i.e. the one it was in the SW scope in). this is more than sturdy enough.

[swamp thing]

Looking real good buddy.

Look forward to seeing it with some varnish on.

[foundaplanet]

Inspiring, making me think I should forget about getting a refractor and build a big dob instead.

Looking very, very good.

[Moonshane]

cheers chaps. me too Steve! debating whether or not to use a stained varnish. perhaps a lighter one like teak. would welcome your advice on this as I have not used varnish that often.

made further progress today. I was not totally happy with the UTA struts and redid them in ply. I am happier now and they look better I think.

also routered out the grip holes in the rocker box and the mirror box. it's easier to pick up now!

also made a hole for the fan and this will be fitted soon with a basic connector added.

the ground board is now done and further holes have been drilled in the truss tube fixings.

next will be establishing the focus point and length of truss poles - they will be about 700mm but need to check before cutting them. I'll use my BGOs to establish the inner focus point as they are the most inwardly focusing eyepieces I have used.

then it's finishing off the metal work, fitting the bearings and cleaning up the whole thing ready for varnish. need to make a truss shroud too and the liner for the secondary cage and it's done! (sounds easy). here's some pics.

[robjohnb]

Great looking Dob you're building there. My effort is of similar size 10" F4.8 but equatorial type (posted on this site).

Would be interesting to compare some built details like the internal aperture diameter of your top section? secondary mirror size?

Rob

[nightfisher]

Shane, thats coming along just nicely, regards finish how about black smooth rite paint, very good at forming a protective seal/shell on objects, so keeping any moisture away from the timber

[Qualia]

The work you are doing here, Shane is simply superb. This is really a beautiful looking telescope and no doubt the views will be as good as the quality of craftmanship going into this beast.

Regarding the paint or varnish finish. I imagine both should offer protection from the elements although the former with an undercoat would possibly add a tad more resitence. Personally, I think whilst you're working this beautiful peice of art, if you like the look of the wood or if you want it to look as natural as possible, I'd go with the varnish finish.

Look forward to seeing more photos

[8kids]

I like the Osmo Polyx Oil range, easy to apply and gives a hard wearing finish. You can get clear or stain versions for exterior use, it is a bit pricy though.

Gary.

[Moonshane]

hi Gary

thanks for the tip. That looks excellent. not cheap but seems a good solution. if it's good enough for floors!......can you apply with a cloth?have you used it on a scope at all? I presume there's no issues with 'shedding' or similar. then again I notice that it's OK for food prep surfaces so doubtful it will not be rock solid in terms of staying put.

[8kids]

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.