Carbon Serrurier truss Newtonian 10" f4 build

[RAC]

I would say this was mostly inspired by another Kiwi Rolf Olsen and his awesome pics. His web page is here.

The main mirror is going to be a Robert Royce 10" f4 conical mirror so there is not need for a fancy mirror cell. The focuser is a modified GSO 3" unit and the secondary is an 88mm GSO one.

I still have maybe 6 months to wait for the mirror(i ordered it last June) so I'll have a play with the GSO 10" f4 mirror for now just to get a few things setup.

The main idea to go with carbon poles over alloy was to get as little focus shift as possible. Without the mirrors currently the total weight is 5.7kg so with mirrors I'll be looking at about 9kg although i still need to mount the dovetail bar but this weight is very low down.

IMG_8240 by Raymond Collecutt, on Flickr

IMG_8242 by Raymond Collecutt, on Flickr

IMG_8247 by Raymond Collecutt, on Flickr

IMG_8526 by Raymond Collecutt, on Flickr

IMG_9080 by Raymond Collecutt, on Flickr

IMG_9087 by Raymond Collecutt, on Flickr

IMG_9094 by Raymond Collecutt, on Flickr

IMG_9104 by Raymond Collecutt, on Flickr

IMG_9112 by Raymond Collecutt, on Flickr

[baggywrinkle]

That is beautifully built, nice to have a workshop as big as that too in which to builf.

Good luck with the final results

[Horwig]

That is one hell of a scope, love the detail in the photos, can I ask what you are going to mount it on?

Looking forward to more photos

Huw

[RAC]

Thanks. The mount I'm using is a older Celestron CGE

[Horwig]

Wow, love the flickr page, I passed through Whangerai Nov 2012, on holiday in NZ, had I known...

Regards

Huw

[RAC]

Got some more work done on it. I'm  using the GSO 10" f4  mirror for setting it up. The mirror is just stuck on for testing purposes.

IMG_9132 by Raymond Collecutt, on Flickr

IMG_9134 by Raymond Collecutt, on Flickr

IMG_9144 by Raymond Collecutt, on Flickr

IMG_9149 by Raymond Collecutt, on Flickr

[RAC]

I also completed the Arduino stepper focuser.

2014-02-02 19.48.44 by Raymond Collecutt, on Flickr

[skybadger]

I'm a bit surprised it balances, to tell the truth.

I'm interested in that you have left the mirror carrier as ply, that the centre cage is so narrow, and that the guider is back on the centre cage. All interesting decisions. What were your design decisions that drove these ?it does look fab though. Hope it performs. I also like your ring layup process-flat on alloy formers?

Regs

Mike

[Robny]

Great craftsmanship, really like the look of this

Sent from my GT-I9505 using Tapatalk

[RAC]

I use an OAG I don't use a finder guider. I only have a laser and a finder scope on the center cage. The cage itself is very VERY stiff. Some guys have gone with two rails all around and some use three(both seem to work) I went for a mix with two but four on the bottom to keep the mounting more stiff. Currently the scope is a bit more mirror side heavy but the GSO mirror in thee atm is 4.8KG and the one the scope is being built for is only 2.8KG as its a conical mirror. I was going to have the a layer of carbon on either side of the ply but 1) i ran out of carbon and 2) the ply is stiff as it is and most people use just ply.

Yeah i used an alloy ring to form the carbon rings, then i placed the alloy with wet carbon face down on an old window to form the other side.

[RAC]

Turns out the GSO 88mm secondary mirror i have has a very bad astigmatism so there is a small 50mm secondary in there just until an Antares optics 88mm secondary turns up.

Collimation seems very stable so far.

This is just 5 x 4min HA subs done with the Atik 383L

Full size here

http://www.flickr.com/photos/46302893@N02/12454722544/sizes/o/in/photostream/

First test of new scope. by Raymond Collecutt, on Flickr

[Luis Campos]

Cheers Raymond,

wow, that look promissing, lovely star shapes! Is this still the GSO primary? If so it looks very good, I'm sure that with a new more pricise secondary you have a winner of a telescope

Congrats!

[michael.h.f.wilkinson]

That scope is a work of art. Really wonderful

[RAC]

Cheers Raymond,

wow, that look promissing, lovely star shapes! Is this still the GSO primary? If so it looks very good, I'm sure that with a new more pricise secondary you have a winner of a telescope

Congrats!

Thanks. I'm hoping its a cheap way out of buying an ASA or Orion optics AG. Yeah that's still the GSO primary just stuck on with 6 small spots of silicon lol. So far the scope without mirrors and focuser has only cost about $500nz but there has been a bit of time put in!

[RAC]

That scope is a work of art. Really wonderful

Thanks sir.

[Chris]

That is some of the very highest class ATM I've come across, what a wonderful scope build congrats!

Chris

[rinaldop]

Congratulations! Beautiful work.

[NickK]

Hi Ray - how did this turn out?

[RAC]

It turned out very well! It's stable as and takes nice pics, It never changes focus over the night. I haven't taken a pic for a few months as the weather hasn't been the best.

Scope and Mount by Raymond Collecutt, on Flickr

M83 Southern Pinwheel Galaxy by Raymond Collecutt, on Flickr

Omega Centauri by Raymond Collecutt, on Flickr

[Mr Spock]

Those are two seriously good images. You must be delighted with the results.

[RAC]

One of the key things for getting the scope working to how i wanted was using a Televue Paracorr. I persisted for far too long with an MPCC. The difference was huge!

Corrector test by Raymond Collecutt, on Flickr

[NickK]

hmm good - my thinking is that I would start with this design in wood for a dob build.. the obvious thing is over time to move to CF.

My gut feeling is that, for an f4 18" mirror (12Kg),  the back end would need a couple of more support bolts and that the bolts are held with a second ring (i.e. the mirror support bolts have the ply ring in front and one behind to keep things parallel. Naturally the balance would be different too.

The next issue for a larger mirror would be - preventing sheering of bolts or the join between the dob base and the centre part of the cage - especially if I try EQ mounting it later.

I'm assuming that you made the trusses out of CF by using a piece of dowel with a release agent and layering around that?

[RAC]

My carbon truss poles came from Hobby king in china at $5.60us each. I'm going to make another scope similar but it's going to be for an 18" f3.3 mirror that I am making and that's only if i can get the figure nice on it and that's proving hard!

I'll be using alloy for the trusses this time though. More like a Royce Dall-Kirkham

http://www.rfroyce.com/DK%20OTAs%20struts.htm

[NickK]

Hmm I used square U section for the spectrograph in it's initial version from a local hardware store.

I found the pieces worked for holding in one direction - however they could twist or be bent in the other directions.

I'd have thought that the mirror would put a large amount of stress on the U piece where the U ends and the tongue then connects via the allen bolts in the design in the link. Alu doesn't bend much before snapping. I'd be tempted to make a test rig with a paving slab in the back to test the stress levels on the Alu. You could run a secured metal line inside the U so that the la is under tension. I still have this image of four small cross sections of alu holding a mirror.

I'd suggest that the end points actually don't have a tongue but instead use all three sides to secure. I found that the stiffest design.

[NickK]

Actually with the back section .. it would be possible to make it a spring loaded/shock absorbing box too.. so that when it's being transported (star parties) the box would act to prevent problems.. hmm food for thought.