View Full Version here: : Any BIG mirrors out there that needs a new home? Even co-laborators.
16-08-2012, 01:03 PM
The bug is nibbling again, so I need to scratch the itch.
I've come across a stunning folded Newtonian that has prooven to the the source of this bug - see the pic below. So I'm now on the road of design and testing for a similar style of alt/az Newt.
To this end, is there any BIG primary that needs a new home? Something in the field of 28" f/4.5. Faster, slower, bigger, smaller. Let me know. I'm also after a source of flat mirrors.
Gary Vecere's scope is a stunning hybrid. I've started corresponding with him over his design. He's told me the design stage was a two year process. His handy work is stunning.
16-08-2012, 03:38 PM
I'm also happy to discuss possible co-laboration with such a project - sharing cost & scope.
16-08-2012, 04:22 PM
Ooooooh nice, good luck dude :thumbsup:
16-08-2012, 05:29 PM
I have the same itch!:)
Resisting scratching it manfully ATM!
16-08-2012, 08:55 PM
I would strongly advise you to explore other (better engineered) telescope designs. Without wanting to put too fine a point on it, that 28" has serious issues that are best avoided.
Incidentally... any idea who made the primary...?
16-08-2012, 09:08 PM
fwiw) I have a 32" f4.5 being made by Mark Suchting...
I am almost reluctant to suggest that I would consider a reasonable offer (on the off chance that someone actually makes one)
16-08-2012, 10:36 PM
Thank you for your words of caution, Clive.
The design is certainly radical, though not unique, in so far as single pole Newtonians goes. Gary's design has issues. But these issues also depend on the application of the scope, and to what the owner of the scope finds acceptable.
Any design would require careful consideration. From my own experience, a first idea would be just be that, an idea. The final design would most likely be very different, taking into acount many mechanical issues into consideration.
What is important is that checks and balances be there, like your words of caution. I am under no illusion that such an instrument presents particular challenges. Foolish I'd be to think not.
It would also be good to get some insight into the scope's actual performance. This would give some insight to what changes could be done to such a design, or what to do to create an improved/different hybrid. That is the way of ATM. May well be that a multi pole folded scope may prove more sound.
17-08-2012, 08:08 AM
I'll write a bit more on the 28" design when I get home from work, but in the mean time, Dan Gray's 28" is worth studying:
17-08-2012, 09:19 AM
Yes, Dan's setup is a very tidy effort, and the Sitech system is great, once you get your head around it.
17-08-2012, 10:15 AM
I've got a bit more details on the single pole Newt.. The round elements are from round clothing racks! Made from chrome plated steel tubes. Talk about crafty, :lol: .
Gary did mention Dan's scope. What detracted him from it was the awkard position of the focuser to use. Yes and no. At close to zenith you would need to crane your neck up for an extended period. Not particularly comfortable. At lower altitude, this doesn't become a problem.
I like the one pole Newtonian design. In an orthodox Newtonian, the smaller secondary creates fewer flexural issues if the pole's diameter is large enough. Work hardening the pole too by giving it a gooseneck further reduces the flex. I've seen this done with a scope to 17.5". A 28" scope is another matter.
Gary's scope also has a couple of trussing elements too, and reaching up the main pole at different heights. These would be mandtory to deal with the massive nature of the secondary mirror and its frame. This trussing deals a lot with the flex. Maybe not ideal for a photographic scope, but may be good enough for a visual instrument.
Effectively, I'm looking to go the minimalist way of design. I'm not looking for a go-to. Push-to at most. Clever, smart design is what it is about. Orthodoxy if fine, but not the only truth. I certainly look forward to your info, Clive. Every bit of information helps as the Newtonian's DNA further evolves, ;)
18-08-2012, 07:51 AM
Did you know hes selling it quite cheap Alex?
18-08-2012, 03:01 PM
Without going in to too much detail, the structure relies too heavily on cantilevered elements so it wont hold collimation and will be plagued with vibration. The focal plane will also be flooded with stray light because there is basically no light baffles to speak of. I would be surprised if this telescope performed even as well as a 20"
fwiw) That particular mirror is not well figured, Gary himself acknowledges that the image quality is noticeably breaking down even with a 26mm eyepiece.
He is prepared to sell the optics for $5K
If you add another $2k for refigure & coating,
then add freight and gst, I suppose you are realistically looking at a bit over $8k.... that is still pretty cheap in the scheme of things.
18-08-2012, 10:52 PM
It was never my intention to purchase this instrument. Nor was it to make a straight rip off of the design. What attracts me is the various minimalist design elements. Forgetting the title of this thread?
I'm curious, Clive, why would you say that this design would be plagued by stray light. I can't see this design being any different to any other open tube design. Including Dan's.
At a dark site, by own big dob doesn't need baffling. The 'baffle' I use at a dark site is more of a dew controlling apparatus.
Dan's design, I cannot understand the reason for the massive struture surrounding the secondary mirror. Any other link available to view the scope? The one below is proving problematic with spam coming up when I try to move through it.
20-08-2012, 09:03 AM
So, any big primary mirrors needing a new home?
22-08-2012, 08:29 PM
Sky light surrounding the secondary folding flat can just flood the eyepiece. Its like a cassegrain without a baffle tube mounted in the primary. Completely open tube Newts without a carefully designed baffle plate in front of the focuser will suffer the same stray light problem.
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