My New 10 Inch.

tnott · #1 19-12-2008, 06:44 PM

Hi all,

Recently I had been looking at the interesting scopes of Albert Highe (also used commercially by Plettstone and Dobstuff) and decided it might be fun to build a medium sized compact scope based on his design. I obtained some secondhand but unused GSO 10 inch F5 optics from someone who had not got around to finishing a scope to put them in and finished it a few weeks ago.

Here's some pics

tnott · #2 19-12-2008, 06:45 PM

Top end is a single ring with a Destiny curved vane spider. No diffraction spikes!

tnott · #3 19-12-2008, 06:47 PM

Bottom end. Side bearings clamp onto poles and are adjustable to trim balance. Side bearings are made from 2 layers of 12mm ply. The outside layer rides on the Teflon, while the inside is slightly oversize to keep the scope from drifting sideways.

Satchmo · #4 19-12-2008, 06:59 PM

Nice bit of work

I've always been a fan of curved spiders too.

Mark

tnott · #5 19-12-2008, 08:12 PM

The rocker box is made out of 12mm ply. The bottom is stiffened by having a second layer on the inside of the rocker sides, also effectively doubling the amount of gluing surface area here. The sides are stiffened by the full height board at the front but also by a semicircular piece at the rear. The circles in the sides reduce weight and act as hand holds for easy lifting. The rocker sits on a triangular ground board via Ebony Star and Teflon, with another shimmed piece of Teflon around the centre pivot bolt to further ease motions.

tnott · #6 19-12-2008, 08:15 PM

With 3 short pieces of tubing, the scope packs up into a roughly 40 cm cube for transport. Will go on the seat of a car.

The whole scope is made from hardwood core, hardwood veneer marine grade Gaboon plywood. Finished with multiple layers of exterior grade polyurethane. A lot more time consuming then painting, but there was a lot of exposed wood surfaces in this scope and it seemed a shame not to show it off.

The GSO optics are a good set and very sharp. The motions of the scope are light and buttery smooth, thanks to Ebony Star, Car Wax, the right PSI on the pads, 70 spacing of the Alt pads, large Alt. bearings and shimmimg around the centre of the Az. pivot.

The large 40mm parallel poles are quick and easy to setup, can conveniently have finderscopes, sliding counterweights etc. fitted to them and are plenty rigid for this size scope. In fact, Plettstone used this design for up to 18 inches of aperture.

Once again, this scope is shroudless, instead using baffles in front of the focuser, behind the secondary and in front of the primary to block stray light.

The scope can either be packed up into a small package for transport, or left assembled and moved around as a whole unit at a moments noticed- it is very light. In fact, this is going to be my new "grab and go" scope at home!

GrahamL · #7 19-12-2008, 08:21 PM

looks great

do your zip ties slip much on the telrad base?

tnott · #8 19-12-2008, 08:59 PM

Good question. The zip ties allow me to rotate the Telrad around to the inside of the OTA so it is out of harm's way when I move the scope around as a whole unit. You can also slide the Telrad up and down if required for balance or a different viewing position, although up the top seems best.

Because the pole it is attached to is along the optical axis it does not get out of alignment when doing this.

I also use the Telrad dewshield with the mirror built in so I can align objects whilst viewing at right angles too.

anj026 · #9 19-12-2008, 09:13 PM

A great design constructed well. Thanks very much for sharing the pictures and info.

GrahamL · #10 20-12-2008, 08:48 AM

Thought you might ,I have my f50 mounted on a truss pole which I twist inside the ota to get it out of harms way, can also usually adjust most small allignments out to.

cheers graham

Paddy (Patrick) · #11 23-12-2008, 06:09 PM

Nice to see that you've started a thread on your beautiful telescope Tim! I was very impressed by it at Snake Valley - lovely to look at, elegant design and so portable.

tnott · #12 02-04-2009, 03:32 PM

Thanks to all for the comments.

I've used it a lot at home over the last few months and it continues to be a great scope for this purpose. Recently flocked the baffles to improved contrast. Didn't seem to noticeany visual difference but it can't hurt!

Starkler (Geoff) · #13 02-04-2009, 05:08 PM

Lovely bit of work there

I wouldnt mind giving my 10 incher the same treatment but cant justify the purchase of tools to do so.

tnott · #14 02-04-2009, 09:36 PM

Tools, what tools!

Actually, I did use a $30 drill+drillstand, some sandpaper+blocks, scissors, screwdrivers, clamps, hammer and paint brushes.

Would've needed a router too if I did not get the wood laser cut.

Re: Curved vane spiders - another ATMer here in SA recently replaced his curved vane spider in a scope because he was sure it caused the secondary collimation to go out when the temperature dropped.

I have not noticed this, but he thought that as the vanes shrunk slightly they caused the secondary to rotate horizontally.

With a straight-vaned spider this of course would not happen as the forces would balance.

Interesting to note if anyone else has seen this effect.

How much would, say a 200mm length of steel or aluminium, expand or contract with a 15degree temperature change?

Starkler (Geoff) · #15 02-04-2009, 10:39 PM

Laser cutting? Sounds expensive.

gmbfilter (Geoff) · #16 03-04-2009, 08:17 AM

Absolutely gorgeous
Truly minimal
A delight just to look at

toryglen-boy (Duncan) · #17 03-04-2009, 10:18 AM

thats a fantastic looking scope.

well done

tnott · #18 04-04-2009, 06:26 PM

Quote:

Originally Posted by Starkler

Laser cutting? Sounds expensive.

$138 for this scope.

Starkler (Geoff) · #19 04-04-2009, 06:55 PM

Was that cutting of ALL the plywood bits including the base?

Does it leave a blackened edge on the wood?

tnott · #20 05-04-2009, 09:58 AM

Yep. All the bits including the feet and pole clamps, where I laminated multiple bits together to make thicker parts.

Got the idea from the Tscopes website. You can also use a CNC router (I don't know if it's more expensive) but you are a bit more limited in the cutting of small parts by the thickness of the router bit. CAD designs must be correct though.

The edges are blackened and about 0.2 mm out of square (the entry side of the laser cut is a tiny bit wider than the exit side in wood).

The edges were sanded to remove the black and to make the important bits square with 2 cork sanding blocks glued together at a right angle, but a disk sander would be quicker and easier. I also used drum sander drill attachment to sand the inside of curves. Took a while, but there is no black left on the finished scope.

With the 16" and 22" I was going to paint them rather than varnish, so not as much time was spent sanding.

This way of going means more time is spent on getting the CAD design right and sanding, but less time cutting parts.