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Art Bianconi
Post Laureate


Reged: 03/06/06
Posts: 4659
Loc: Delaware River Valley, New Jer...
I want a Fork Mount!
      #1033232 - 07/07/06 09:19 AM Attachment (168 downloads)

In preparation for taking the Schief to Stellafane, I made some improvements to the crutch based retro mount.

Schief with Retro Mount

This tripod is remarkable and I must acknowledge Wayne Petko of NJAA for turning me on to the design! The stiffness of such a light (3.5 pounds) is such that it amazes all the ATM's and astronomers who use it. And me too!

The weak point in my system is not the tripod but the original CA-4 German equatorial mount. It was not designed for so heavy a cradel and while I have developed a a new, all composite cradel design, the thing I dislike most about the system is the GEM design.

Last night seeing conditions were fairly good but the scope was at such an angle that in order to view Jupiter, or the moon, I had to do that common GEM dance of flipping the scope upside down and over the top of the mount.

Such acrobatics severely test the mechanical rigidity of any OTA and are, I am sure, one reason for the popularity of Dobsonians, whose simple point and shoot use makes life easier.

I will wait until my return from Stellafane before articulating a fork replacement. I have designed one fork system thus far with a sector drive but that was for a conventional open truss Newtonian, not a Schief, so I am starting out with a "clean sheet of paper".

I don't see many fork mounts around CloudyNights, with or without motors. That concerns me. Still, if you guys have any ideas you'd like to see tested, now is the time.

Here is one very nice example built by David Harbour.

Thanks

Art
======================

Attachment

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“Everything is on its way to somewhere. . . . . everything!"

____________________ George Malley (John Travolta)
________________________ "Phenomenon"


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GordonCopestake
Carpal Tunnel


Reged: 03/02/06
Posts: 2715
Loc: Newcastle-under-Lyme, UK
Re: I want a Fork Mount! new [Re: Art Bianconi]
      #1033675 - 07/07/06 01:58 PM

Thats a fantastic fork design! I wonder how stable it is on those rails.

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Art Bianconi
Post Laureate


Reged: 03/06/06
Posts: 4659
Loc: Delaware River Valley, New Jer...
Re: I want a Fork Mount! new [Re: GordonCopestake]
      #1033686 - 07/07/06 02:08 PM Attachment (109 downloads)

Over the years David Harbour has demontrated a lot more than just great telescope designs. He has patents all over the place, including one for a sector drive that uses a hardware store threaded rod and which has zero periodic error!

That scope is just one of a similar design philosophy, a Cass that used an 18" primary.

I urge you to do a Google on simply his name: "David Harbour" and then sit back! When you get to his writings on "Understanding the Faucoult Test" you will see the most lucid, easy to understand explanation of that test, that has even been written, including hand drawn images by David himself.

Enjoy

Art
====================

Attachment

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“Everything is on its way to somewhere. . . . . everything!"

____________________ George Malley (John Travolta)
________________________ "Phenomenon"


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Undermidnight
BEOTS "Tweener Cup" winner


Reged: 05/25/04
Posts: 3411
Loc: Hilliard, Ohio
Re: I want a Fork Mount! new [Re: Art Bianconi]
      #1033762 - 07/07/06 03:16 PM

Yes, David Harbour is an asset to the ATM community. His foucault testing article really allowed it to "click" for me.

Someday I really want to make one of those!

Jason

--------------------
"There's only two things that excite a man, expensive toys and real expensive toys." - Red Green

WO Zenithstar 66 on Microstar Mount
8" Ultima 2000, "Wilma"
8" F/4.2 Ultralight, "Marilyn II"
12.5" F/4.3 Ultralight, "Ada II"
11x70 Oberwerks
6" F/6 Figuring
Pans, Orthos, and Naglers
"We who cut mere stones, must always be envisioning cathedrals." - The Quarry Workers Creed

http://www.undermidnight.com


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theoUK
sage


Reged: 04/22/04
Posts: 340
Loc: N. Yorks, UK
Re: I want a Fork Mount! new [Re: Undermidnight]
      #1034076 - 07/07/06 08:26 PM

Hi,

I really don't see hte problem with the GEM. To my mind its the most logical system. A fork always requires some large counterweights to get the centre of gravity low enough to have short 'tines'. If 'flipping' with a GEM is a problem, why not just put rotatable bearings and a locking mechanism in the tube rings (or equivalent to tube rings)? I only have a 6" newt so its not a problem to slacken the rings and quickly flip the focuser for east and west viewing but if I'm ever lucky enough to own a big newt (and still need it to be portable) I'd definately make a rotating cradle of some kind.

But maybe for the Scief.. a fork is better because the design has a centre of gravity near the eyepiece.
Just my 2c,
Theo

--------------------
12" F4 Orion Optics / Galvoptics UK DIY Newt
Beacon Hill EQ mount
DIY stepper and guide drives
Surplus shed 127mm f5.5 carbon poochromat


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Starman1
Vendor (EyepiecesEtc.com)


Reged: 06/24/03
Posts: 17639
Loc: Los Angeles
Re: I want a Fork Mount! new [Re: theoUK]
      #1039380 - 07/11/06 04:02 PM

I'm one who believes a fork mount is the best mount for the newtonian:
--you can pass from horizon to horizon without hitting a mount.
--the center of gravity is very low
--no counterweights are required
--the eyepiece can be even lower than a dob.

But:
--the tube has to be very rigid
--the bearings have to be very strong because of intense side load

Nonetheless, I was blown away, a few years ago, when I saw a 12.5" Lightspeed telescope on this knd of mount.
I admire the machinists who can make themselves a mount that operates this way.
Good call.

P.S.Only one mount is superior to this--it's called an English Yoke. But it's intended for permanent mounting.

--------------------
Don Pensack
www.EyepiecesEtc.com
12.5" Teeter/Zambuto, 5" Maksutov
Sustaining Lifetime IDA member



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llanitedave
Humble Megalomaniac


Reged: 09/26/05
Posts: 20063
Loc: Amargosa Valley, NV, USA
Re: I want a Fork Mount! new [Re: Starman1]
      #1039508 - 07/11/06 05:27 PM

I agree about the potential of a fork mount. It's more bulky than a GEM, but not necessarily heavier. The designs are much simpler. And I always hated having to switch things around at the meridian.

I played with the idea of making a lightweight, portable fork for my 10", even went so far as to cut the supports, but then decided to stick with the dob design.

--------------------
"Truth" is that which confounds our expectations...

Science is a bazaar, not a cathedral




"S.O.E." (Sauron's Other Eye), with 16" Royce conical mirror: A permanent work in progress.

The "Eye of Sauron" Observatory Open for Business!


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Roy McCoy
Pooh-Bah


Reged: 10/13/05
Posts: 1030
Loc: Glendale, AZ
Re: I want a Fork Mount! new [Re: Art Bianconi]
      #1039673 - 07/11/06 06:49 PM

Hi Art

You may have looked through the other pages from the last post, but if you hadn't seen it C. J. Park's built a wooden fork on a wedge.

And John Biretta, Jeff Hutton and Dick Wessliong's award winning Schiefspeigler is over to the left.


--------------------
AstroTech 106
'86 Christen triplet 6"f/8


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Art Bianconi
Post Laureate


Reged: 03/06/06
Posts: 4659
Loc: Delaware River Valley, New Jer...
Re: I want a Fork Mount! new [Re: Roy McCoy]
      #1039969 - 07/11/06 10:35 PM

Roy, I missed these. As for Dick Wessliong's Schiefspiegler: I've built one and I've seen others made from Dave Groski's designs. I'd never have guessed that Wessliong's was a Schief! Live and learn!

Park's fork design is a thing of beauty!

Thanks for the link.

Art
================

--------------------
“Everything is on its way to somewhere. . . . . everything!"

____________________ George Malley (John Travolta)
________________________ "Phenomenon"


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Art Bianconi
Post Laureate


Reged: 03/06/06
Posts: 4659
Loc: Delaware River Valley, New Jer...
Re: I want a Fork Mount! new [Re: Starman1]
      #1039983 - 07/11/06 10:45 PM

Hi Don!

Both of my latest truss designs employ forks. The 8" and the 15" you see listed below.

My 12.5" F8 "Planet Killer" is on a GEM and I need a ladder like those you see blocking the isles at your local Home Center, to look through it. A fork mount would chop that height by 5 feet!

Both the 8" and 15" will be portable and while the loads on the fork for the 8" will be relatively mild, it will still be made up from layers of bi-birectional and Uni-directional fiberglass laminated on both sides of a foam core.

Once the flat sheets are made up, it's relatively simple to build up the fork with the mechanical stiffness it needs. You're absolutely right about that. Where I am still fussing and figeting is the design of the declination drive and the attachment of the OTA to the drive.

I've stuff I must do before leaving for Stellafane in a few weeks. However, as soon as I return, I will jump on then 8" PortaScope (Carry-on-legal).

What I learn building that, will be used to enhance the design of the 15" F-4.3

Thanks for the encouragement!

Art
==================

--------------------
“Everything is on its way to somewhere. . . . . everything!"

____________________ George Malley (John Travolta)
________________________ "Phenomenon"


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Tom L



Reged: 01/07/04
Posts: 31037
Loc: Sunny Oregon
Re: I want a Fork Mount! new [Re: Art Bianconi]
      #1040019 - 07/11/06 11:16 PM

The C. J. Parks fork design is a sweet mount! I would love to make something like that for my 8" f/6.

--------------------
Tom
Tele Vue 102mm f/8.6 on an EzTouch
Vixen 80mm f/5 A80SSWT on a grab-n-go mount


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Biff
Carpal Tunnel


Reged: 09/04/05
Posts: 2562
Loc: Tampa, FL
Re: I want a Fork Mount! new [Re: Tom L]
      #1040029 - 07/11/06 11:35 PM

Has anyone used a mount like this? It looks very capable mechanically speaking but looking at C.J. Parks design it looks as though the mount would seriously be in the way of my feet at certain locations.

Ryan

--------------------
Ryan


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gazerjim
Postmaster


Reged: 02/12/04
Posts: 8166
Loc: n-dimensional space
Re: I want a Fork Mount! new [Re: Biff]
      #1040043 - 07/11/06 11:53 PM

Looking at those mounts, the words "elegant design" come to mind. The only arrangement I might prefer (if I ever have a permanent setup) is a split ring.

But those forks are indeed real beauties!

Jim

--------------------
Jim Fisher

"How wonderful that we have met with a paradox. Now we have some hope of making progress."

Niels Bohr


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Roy McCoy
Pooh-Bah


Reged: 10/13/05
Posts: 1030
Loc: Glendale, AZ
Re: I want a Fork Mount! new [Re: gazerjim]
      #1040094 - 07/12/06 12:51 AM Attachment (98 downloads)

Art

I didn't notice if you are interested in a fork on an equatorial or just alt/az.

I was intrigued when I ran across this mount, though I can't remember where I saw it (maybe someone knows the link). There is a group making mounts (in the UK I believe) that look similar to the pic below.

Attachment

--------------------
AstroTech 106
'86 Christen triplet 6"f/8


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David Knisely
Postmaster


Reged: 04/19/04
Posts: 13646
Loc: southeastern Nebraska
Re: I want a Fork Mount! new [Re: Roy McCoy]
      #1040115 - 07/12/06 01:16 AM

That mount is an "inverted fork". In the image, it is clearly in an altazimuth configuration, but such a mount has been "tilted" over to create an almost unique inverted-fork equatorial. A 4.25 inch Newtonian is shown mounted on one with the full construction details in Richard Berry's book BUILD YOUR OWN TELESCOPE. Clear skies to you.

--------------------
David W. Knisely . . . . . . "If you aren't having fun in this hobby, you aren't doing it right."

Hyde Memorial Observatory
http://www.hydeobservatory.info
Prairie Astronomy Club
http://www.prairieastronomyclub.org


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dawsonian2000
Pooh-Bah


Reged: 07/26/06
Posts: 1434
Loc: Riverview, FL, USA
Re: I want a Fork Mount! new [Re: David Knisely]
      #1062398 - 07/27/06 02:41 AM Attachment (91 downloads)

Art

Just became a member of Cloudy Nights, as well as my friend and colleague Gary Barabino. I am in the process of building a 10" f/5.65 Newtonian EQ Fork Mounted reflector. I faced the same dilemma some time ago in search for a viable Equatorial Fork Mount design and decided to set out and develop one of my own. So after a long and orduous amount of time, I systematically developed a working design - section by section. In doing so I figured I would make my information available to other ATM'ers in the form of a website that covers the step-by-step process. I have just recently completed the fork mount, but I am in the process of updating my website with the most current photos and steps. But in the interim, I am attaching a photo of the mount I just completed this past weekend. As for the telescope, I used a 12.250" x .250" thick Sonotube laminated with epoxy. The finishing process (painting and assembly) will commence soon. So, when time permits, I hope all interested amateurs will visit our site and find some useful information to help them in their astronomical endeavors.

Attachment

--------------------
Clear Skies, Forever!
The Vega Sky Center
10" (254mm) F/5.65 Homebuilt Fork Mounted Newtonian Reflector
5" (127mm) F/9.4 Homebuilt Refractor
4" (100mm) F/13 Carton Homebuilt Refractor
3.1" (80mm) F/6 Scopos ED APO Refractor
4.5" (114mm) F/8 Tasco 11te-5 Newtonian (under restoration)
2.4" (60mm) F/16.7 Tasco 7te-5 Refractor
2.4" (60mm) F/15 Jason Discoverer 313 Refractor

http://www.vega-sky-center.com


Edited by dawsonian2000 (07/27/06 03:45 AM)


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Chriske
Kijkerbouw Urania


Reged: 08/15/04
Posts: 2317
Loc: Boechout, Belgium
Re: I want a Fork Mount! new [Re: dawsonian2000]
      #1062426 - 07/27/06 03:43 AM

Very nice mount Mel...

--------------------
Chris



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dawsonian2000
Pooh-Bah


Reged: 07/26/06
Posts: 1434
Loc: Riverview, FL, USA
Re: I want a Fork Mount! new [Re: Chriske]
      #1062429 - 07/27/06 03:56 AM

Thanks, Chris! It was indeed a joy to build. Hope others can benefit from the designs I have devised and posted on our website. My initial tests of the mount and OTA proved successful during our first light session conducted with my friend and associate Gary Barabino on July 14, 2006. Just have to paint and finish the OTA.

--------------------
Clear Skies, Forever!
The Vega Sky Center
10" (254mm) F/5.65 Homebuilt Fork Mounted Newtonian Reflector
5" (127mm) F/9.4 Homebuilt Refractor
4" (100mm) F/13 Carton Homebuilt Refractor
3.1" (80mm) F/6 Scopos ED APO Refractor
4.5" (114mm) F/8 Tasco 11te-5 Newtonian (under restoration)
2.4" (60mm) F/16.7 Tasco 7te-5 Refractor
2.4" (60mm) F/15 Jason Discoverer 313 Refractor

http://www.vega-sky-center.com


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Art Bianconi
Post Laureate


Reged: 03/06/06
Posts: 4659
Loc: Delaware River Valley, New Jer...
Re: I want a Fork Mount! new [Re: dawsonian2000]
      #1062509 - 07/27/06 06:59 AM

Mel, I went to the site. I am limited to a dial up modem and lousy phone lines so I was only able to browse a little bit. The mount looks nice. I'd love to see details on any declination drive you might be using and how it attaches.

That's where I am having difficulty.

Thanks

Art
====================================

--------------------
“Everything is on its way to somewhere. . . . . everything!"

____________________ George Malley (John Travolta)
________________________ "Phenomenon"


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PeglegOS
sage


Reged: 06/08/06
Posts: 418
Loc: Parma Heights, Ohio (Cleveland...
Re: I want a Fork Mount! new [Re: Art Bianconi]
      #1062725 - 07/27/06 09:46 AM

Mel,

Man, I'd LOVE to build that one. Great work! Nice site too...

--------------------
--8 & 21 MM Stratus EPs--
--2x Orion Shorty Barlows--
--Celestron Omni 120 XLT f8.3 Refractor--
--Zhumell 8" Dobsonian--
--Celestron 102mm Wide View--
--UA Unistar Light Basic--
--Orion Astroview 6 EQ--
--Telrad--
--Rigel Quickfinder--
--Nikon D50 DSLR---

------Walter E. Schuele Planetarium-----




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