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20" f/4 Dob build

swamp thing

By swamp thing
in DIY Astronomer

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  • 1 month later...
swamp thing

swamp thing

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Thought I'd post an update as I'm starting to get PM,s asking what's going on.:(

I'm currently awaiting parts (focuser and altitude bearings)from the states. I need these parts before I can start on the mirror box. As before I build the mirror box I need to know the exact weight of the UTA

Thanks for all the pm,s and encouragement.

Ps I tried my "super finder" handheld, tucked under my arm, the other night and all seems okay with that.:(

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Moonshane

Moonshane

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Thought I'd post an update as I'm starting to get PM,s asking what's going on.:(

I'm currently awaiting parts (focuser and altitude bearings)from the states. I need these parts before I can start on the mirror box. As before I build the mirror box I need to know the exact weight of the UTA

Thanks for all the pm,s and encouragement.

Ps I tried my "super finder" handheld, tucked under my arm, the other night and all seems okay with that.:(

cheers for the update Steve.

I know how frustrating it is waiting on parts. Thankfully my bits came quickly.

The parts you have ordered are top drawer so will definitely be worth waiting for. In the meantime, fancy coming up north and doing some sanding? (my most hated task of all).

Look forward to more progress in due course.

Shane

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Daniel-K

Daniel-K

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steve in a few years when you get board and make that 30" first dibs on the 20" :( im struggling to finish my mirror at the moment the sister inlaw has rammed our garage with stuff for her house move so im at a stand still, can i ask what are the bearings you using?

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swamp thing

swamp thing

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:DSteady on Danny, I havent even finished it yet and you're making eyes at it.:(:(

I would need to alter the front of my house to get anything bigger in, TBH may have to alter the doorway a bit for the 20" to go through easily anyway.:) glad I'm a builder.:(

the alt bearings are from "Webster" scopes. Here:

http://www.webstertelescopes.com/Aluminum_Altitude_Bearings.htm

I'm going for the 30" ones as Eric Webster says at f/4 with these I shouldnt need to counter weight the scope at all. The larger surface area making it hold better apparently.

They will also be black anodised.

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Moonshane

Moonshane

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I totally agree with your comment on alt bearings Steve.

This in my opinion is a major design flaw with off the shelf dobs as they make the alt bearing so small in diameter.

a larger diameter bearing puts the bearing point lower and this either allows you to make a lower rocker box/smaller mirror box or to make a slightly higher one to suit your favoured observing height. also as stated there's more bearing surface to create more friction and therefore it will hold. I'll not have to counterbalance my 6" truss dob either as I have 12" diameter bearings, a full 2x the diameter of the mirror.

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swamp thing

swamp thing

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Been sitting around doing zip because of the constant rain. Cannot work, cant work on the camper, nowt to do on the scope.

All of a sudden I've recieved an email from Eric saying my parts are being packaged up ready for shipment. Hooray! :)

So looking forward to getting on with this scope it was beginning to hurt.

Should get the parts in a week or two outside.

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umadog

umadog

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Filter slide is very wonderful. I use my filters (UHC and OIII) a lot more since I installed it. I have Astrocrumb slide (http://www.astrocrumb.com/). I use the one that's directly screwed into the OTA. There is also a version that screws into the Feathertouch but that sticks further into the light path. I've even seen a customised OTA where the slide is incorporated into the tube wall so as to protect the filters from dust and dew. The Astrocrumb has an optional dew heater.

You may find that the Webster truss pole clamps (the hinged ones for the UTA) will slip on the poles. Mine do, anyway. My solution was to place a little thin rubber between the clamp and the pole. I also wrapped a little rubber strip around the truss pole beneath each clamp. I secured the strip with a cable tie. My clamps are now a lot more solid.

Which parts did you choose to get from Eric?

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swamp thing

swamp thing

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That slide does look rather nice. Thanks for the link. The dew heater would be a good option over here :D

That's got me thinking again :confused:

The upper truss clamps ive got seem to grip like an angry alligator. Maybe my tube is slightly thicker?

I will keep an eye on them though when it's all up and running.

The parts are the altitude bearings. Didn't fancy making wooden ones as I prefer the look of the metal I also ordered the feathertouch from him as it means only one import and his prices seem as good as anywhere else's.

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umadog

umadog

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Interesting. I wonder what the difference is... Do the inside of your clamps have any rubbery plastic? My clamps contain two plastic rings which hardly grip at all.

I'm with you on the bearings. They're nice: you'll like them.

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swamp thing

swamp thing

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Maybe, either the tube I'm using is a slightly larger diameter than yours (my tube is 1.5" diameter exactly) or Websters have altered the design slightly. There is no rubber insert or plastic rings inside.

Maybe the slot is wider and allows it to grip more. Perhaps some people complained and they changed the design, don't know. But. Bar gabbing the tube with slip jaw pliers and yanking like a mad man you'll never pull them out (TBH not even sure you'd get it out doing that). They grip extremely well. I have to slacken them right off to move the tube in and out.

Sounds like it might be worth your while sticking a post on CN Rob, see if anyone else has your problem.

Not sure there are enough Webster scopes over here to make a post here worthwhile. I have only ever seen one over here and that was the one that made me want their hardware.

Or, you could maybe give Eric a shout and see if the design has been changed.

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  • 2 weeks later...
swamp thing

swamp thing

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The SIPS Feathertouch focuser came today, thank god :hello2:

I must say it looks a lovely piece of kit (I'll take some photos later). Nicely put together and smooooooth :afro:

It comes with a CD with full instructions that do look pretty comprehensive (I managed to blag a computer to have a quick gander earlier today).

Even better than that all my predrilled holes line up perfectly so it's going to be a superb fit (I always worry a bit working off drawings).

I shall fit it in a day or two and post some pictures as I go.

Then it's just fit the rest of the UTA bits and pieces, telrad etc, weigh it, then I can start on the mirror box.

The alt bearings haven't arrived yet though :( Hope they haven't been lost. :eek: . The focuser was delivered by parcel force :eek::eek: I'm not their biggest fan I must say.

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swamp thing

swamp thing

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No good I couldn't wait. Combination of impatience and zip on TV got me deciding to fit it tonight. :D

First job is to fit the focuser base plate. This goes straight onto the UTA in the holes I drilled earlier.

As you can see the base plate has four adjusting allen screws to adjust it for square onto the UTA. As I'm only fitting I'll adjust these later.

7813340b.jpgNext the Paracorr section, this is is in two pieces. The optical part and a spacer tube. They are threaded together.40ad58fe.jpgThese are held onto the base plate by a mounting ring and secured by alen grub screws.682bc490.jpgHere is the Paracorr section in place you can clearly see the optics and the mounting screws for the focuser itself.6c0011d5.jpgNow the focuser itself, locating on top of the Paracorr and held in by more Allen grub screws.43b50fed.jpgThe Paracorr section can be unscrewed from inside the UTA for collimating it has a knurled section on the end for grip.Not a good pic but you get the idea.6911dc12.jpgAnd here's the complete focuser.933f2ef3.jpgVery simple and easy to do :)

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