254mm F4.5 Compact Dob

[CoombellKid]

Originally Posted by stringscope

Thanks Rob. That is good to know you can bend it lengthways, where do you get the 0.7mm ply from BTW??

Actually what happen was I went into town and inquired at a hardware store. I knew you could get 1.5mm and the hardware bloke had never
heard of 1.5mm ply and didn't quite believe me so he rang his supplier.
It was the supplier that said he had 3 ply down to .7mm which amazed
both of us. But I went with the 1.5mm as I thought it would be better
for a SC wall.

That was Thrifty Link Hardware in Casino, but I suspect they probably go
through Lismore Timber and Ply.

regards,CS

[stringscope (Ian)]

UTA now has a couple of coats of polyurathane, the focuser and truss attach bolts fitted and put to one side.

Started work on the mirror box. Cut 4 sheets of 12mm ply, 12 strips of Jarrah and started gluing the whole lot together. Mirror box will have internal dimensions of 360mmX360mmX500mm.

[tnott]

Great project. Thinking about making a compact 8"-12" dob myself for when I don't have enough room on family trips etc. for the big one.

[stringscope (Ian)]

Originally Posted by tnott

Great project. Thinking about making a compact 8"-12" dob myself for when I don't have enough room on family trips etc. for the big one.

Agreed You can get a pretty good astro "fix" with an 8-12" scope, particularly from a dark site. No ladder required for a 12" F5

[stringscope (Ian)]

Continued glueing the Jarrah edging onto the mirror box sides tonight.

[stringscope (Ian)]

Mirror box sides trimmed, sanded and glued up.

[stringscope (Ian)]

I have had a few distractions like .............. work and gardening

Mirror box all glued up a couple of weeks ago and UTA fits as advertised.

I have now got around to starting work on the 6 point morror cell. All the major parts are cut out from 20mm square steel tube. Pivot arms from 15mm. Edge support points @ 45 degrees. Parts laid out to show arrangement. Planning to drill all holes and fasten parts to board tomorrow night in preparation for welding.

Cheers,

[stringscope (Ian)]

Cell frame and support points complete.

Mirror retaining clips added.

45 degree edge supports and collimation rods to go.

[Starkler (Geoff)]

What a beautiful thang

[stringscope (Ian)]

Hi All,

What with work, Christmas and a medical issue I have not had mch spare time of late. However, I have now managed to get back to this job.

Focuser, spider and secondary now mounted in UTA.
Primary mirror cell finished and mounted on rear plate.
Primary mirror baffle fitted.
Focal plane position established giving 400mm gap between top of MB and bottom of UTA.

Cheers,

[GrahamL]

very nice Ian .. not far off now ?

[stringscope (Ian)]

The mirror box has had a couple of coats of polyurathane, steering handle fitted to the UTA and tonight a trial fit of the truss assembly.

UTA has been shortened by 12mm so as to be flush with the top of the MB when nested inside the MB.

The truss should be 20mm longer than optimal length at this stage. I will shorten as required once I have double checked the focal plane position.

Cheers,

[stringscope (Ian)]

Yep, needed to shorten the truss by 20mm as planned - better then having to try and lengthen it though . Mounted the finders and initial check on CofG position.

Clouds cleared for a little while tonight so I centre spotted the primary, spent some time on an accurate collimation and took the scope outside for a first light.

As expected Paracor is a must @ F4.5. Initial impresion of the mirror is a good one, nice "snap to focus" and no sign of astigmatism. Seeing wasn't the best so didn't get above about 145X. The mount wasn't up to tracking at higher mags either .

[tnott]

Very cute scope. I like the woodwork especially.