Looking for a 10-14" primary mirror

[Akshay Subramaniam]

I've been meaning to get back into visual astronomy and realized the hard way that using my imaging newt for visual is massively inconvenient. I thought it would be nice to try and build a medium size dob instead and wanted to see if anyone had a relatively inexpensive 10-14" newtonian primary they're willing to sell. GSO or similar quality is fine, not really looking for the highest quality optics at least for now.

Thanks,

Akshay

[pnal...@gmail.com]

If you are going to GSSP, I have one for you, a 12”. Or,  if a friend is going and can take it to you, that is fine, too. Is $0 relatively inexpensive enough?

 

This mirror is in a home-made wooden fold-up small-footprint telescope, owned by our old friend Jeff Gortatowsky. After Jeff’s passing, I acquired it from his sister, who just wanted everything gone from Jeff’s storage unit… so I grabbed it. Little did I know at the time that there were metal struts between the wooden upper and lower structures. I actually saw these on the floor of a very crowded storage bay and did not recognize them for what they were and I am now unable to assemble the thing. The mirror in it looks pristine. The original telescope was an Orion Sky Quest Intelliscope, but attached is a picture of everything as it stands now.

 

Let me know, we are anxious to get the space back in the garage. I really wish I had those struts, I would like to use it myself but am no longer up to such a project.

 

Of course, I could always salvage the mirror, mirror cell, focuser, secondary, etc. and just junk the wood, if you prefer. Let me know.

 

\Paul Alsing

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[Mark Wagner]

I know how to assemble the mount, clamshell rings and large altitude bearings    the mount folds flat for transport/storage.  Ashkay, I can help you with it if you're interested.

[pnal...@gmail.com]

All that is pretty easy, Mark, but the struts are definitely missing. They either need to be “copied” from an existing set or some other kind of structure designed to replace them. They seem to be easy enough to make, just straight tubing with flattened ends and angle-iron connectors, but I have not been able to find drawing or dimensions and I have spent s a lot of time looking.  Attached is a very poor picture of them, the best I could find. The mates to these live on the original Orion metal pieces. Sadly, I’m just not up to doing this kind of stuff anymore

 

\Paul

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[Alex]

Imho, the image of struts is good enough to infer all the needed dimensions for DIY manufacturing. As soon as all of them are of an equal length (I'd keep them on a shorter end) the only error remaining is in the assembled UTA height. Which should be small enough to compensate with adjustments of the primary collimation and the focuser draw (if the estimated length kept on the shorter end, the focuser simply goes a bit farther out. The secondary obstruction error can be ignored. Just my 2c.

[Akshay Subramaniam]

Thanks for the offer Paul! I was on the fence about going to GSSP but this might help make my mind up :) I'm not sure I totally follow what the issue with making/finding replacement struts is. But I think I can find some solution to it. After all, part of the appeal of building a scope for me is to learn about all of these intricacies.

Thanks,

Akshay

[Akarsh Simha]

On Mon, Jun 2, 2025 at 3:03 PM Mark Wagner <itsmar...@gmail.com> wrote:

I know how to assemble the mount, clamshell rings and large altitude bearings    the mount folds flat for transport/storage.  Ashkay, I can help you with it if you're interested.

Yeah, looks very curiously like it was made by a guy in Los Gatos.

 

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[Akarsh Simha]

On Mon, Jun 2, 2025 at 7:02 PM Akshay Subramaniam <aksha...@gmail.com> wrote:

Thanks for the offer Paul! I was on the fence about going to GSSP but this might help make my mind up :) I'm not sure I totally follow what the issue with making/finding replacement struts is. But I think I can find some solution to it. After all, part of the appeal of building a scope for me is to learn about all of these intricacies.

Good truss clamps are hard to make. Moreover, I'm not sure if we can find the flattened-end rods of the right length, but regular round tubing should be very easy to acquire.

I recently acquired Aurora Precision's truss clamps for my 28-incher. I haven't yet worked on installing them, that's on my pre-GSSP list (if I manage to find time between work and other commitments). They were pricey, although the price is par for the course since they aren't mass-manufactured. The way these work is that they use tube inserts and brackets instead of flattened rods. That may be easier for a hobbyist. Wonder what Albert Highe did on his scopes.

One could build some solution anyway, it's not rocket science.

I'm very happy to join you "metal shopping" at Industrial Metal Supply Co. I need some angle aluminum myself.

Regards

Akarsh

PS: Having built a rocker box, I developed a desire to build a full telescope. Nevertheless I have way too many interesting things and probably won't give this as much time. So perhaps I'll enjoy it vicariously.

PPS: I will have a 12-inch mirror for sale, I think, although many years down the lane.

Thanks,

Akshay

On Monday, 2 June 2025 at 16:52:17 UTC-7 alex.k...@gmail.com wrote:

Imho, the image of struts is good enough to infer all the needed dimensions for DIY manufacturing. As soon as all of them are of an equal length (I'd keep them on a shorter end) the only error remaining is in the assembled UTA height. Which should be small enough to compensate with adjustments of the primary collimation and the focuser draw (if the estimated length kept on the shorter end, the focuser simply goes a bit farther out. The secondary obstruction error can be ignored. Just my 2c.

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[John Pierce]

Any tubing can be flattened with the appropriate tool.

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[Akshay Subramaniam]

Good truss clamps are hard to make. Moreover, I'm not sure if we can find the flattened-end rods of the right length, but regular round tubing should be very easy to acquire.

My thinking was that one could use regular round tubing and use some clevis connector inserts to mate them to a flat plate like the SkyQuest scopes seem to use. If that doesn't work due to off axis loading of the trusses, it seems reasonable to use heim joints with similar tube inserts or DIY inserts. These also have the added benefit of not needing to have perfect length tubes and have some adjustability. These are all completely untested ideas, maybe there's more to this than I am able to appreciate at this moment.

I'm very happy to join you "metal shopping" at Industrial Metal Supply Co. I need some angle aluminum myself.

I'm not very familiar with sourcing materials, so I might take you up on this and tag along whenever you go next :)

Thanks,

Akshay

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[Peter Santangeli]

If you have access to a 3D printer you could get some carbon fiber tubes (aliexpress... amazon...) and then print out end pieces.

That's what I did for my latest astrograph. I used carbon fiber tubes, printed out end pieces that just fit, and then used JB Weld to glue them into the tubes.

I used ASA-CF (ASA with embedded carbon fiber) for strength and weight.

pete

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[Akshay Subramaniam]

That’s very interesting! I do have a 3D printer and just got some PET-CF anticipating it would be useful for something like this. I would’ve expected a fully printed end piece would flex a lot more than ideal but if it works well for your astrograph, it’s probably good enough for this!

Thanks,

Akshay

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[Mark Scrivener]

3D printed with ASA would probably be good enough. My old Obsession seems to hold collimation (while setup) and those poles are simply inserted in holes drilled into plywood blocks. 

But It wouldn't be too hard to mill parts from aluminum. Lots of folks in this group have small (and not so small) mills in their garage. If you were clever you could probably even make the parts on a lathe, and there are even more of those floating around the group.  Aluminum parts would be a bit more temperature stable and less likely to fail.

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[James Webster]

I have a 10 inch mirror I made in John Dobsons mirror making class, that I haven’t used in years, that I would be willing to sell for $200.

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[Richard Navarrete]

Hi James,

What focal length is your 10” mirror? Does it have a good figure and coating?

Thanks,

Richard

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[Akarsh Simha]

Fascinating ideas here.

BTW, I learned from an experienced telescope maker that "carbon fiber" poles are normally made from carbon fiber "fabric" attached to an acrylic tubing. Apparently, the acrylic is easy to break, so one must be careful with the tubes.

Regards

Akarsh

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[Alan Agrawal]

Yep, I have heard carbon fiber tubes don’t do well if significant lateral pressure is applied.

Alan

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[James Webster]

Hi Ricard,

The focal length is 6.3 I believe. The coating is relatively new. The figure is good. You could have the entire telescope if you want. I have a relatively large collection of telescopes. Some don't get used.

James Webster 

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[Jaimie Henderson]

Hi Akshay,

I have a 14" Orion xx14g with blown circuit boards, so the goto / tracking no longer works (long story...). While I was trying to get the boards repaired, I decided to upgrade to an 18" Obsession, and the 14" is now just taking up space in my garage. I have a potential buyer for the scope but if he's not interested I'd be happy to let go of it cheap. The mirror is pretty good IMO, but of course nowhere near the caliber of the Ostahowski in the Obsession. It's given me many years of happy observing as an upgrade over my trusty Orion 8" Dob. I believe I paid $2800 for it new, I'd be happy to let it go for a fraction of this, if you'd be willing to come to Redwood City to get it.

You can email me directly if interested.

Jaimie