Chriske
Kijkerbouw Urania
Reged: 08/15/04
Posts: 1953
Loc: Boechout, Belgium
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This platform is very easy to build.
Basically it's nothing more than a box, hinge, and a threaded rod.
The hinge is placed at an angle, matching our latitude and the threaded rod is there to do the tracking work.
Up to two hours of tracking can be done with this mount.
Usage :
1- Small to very large telescopes.
2- Reflector (mostly Newtontelescopes).
3- Transportable.
Looking north-west Mount fully opened ready to start tracking
Large image
Looking west
Large image
The lower and upper part of the mount are connected with only a hinge and a threaded rod. With a scope on top of this mount the scope is absolutely not stable, it will make a rocking motion around these two points.
To prevent this there are some glidingblocks at the westside of the mount. These blocks are mounted parallel with the threaded rod. These gliding blocks have a layer of teflon and the other a layer of formica to asure smooth tracking. With these extra blocks installed this mount becomes rocksteady and can handle very large weights.
In case of very large scopes you need to install an airpump to relieve the threade rod from all that pressure. ( I use a reardoor airpupm out of a car)
Looking south. Mount fully opened.
Large image
Looking south. Mount fully closed
Large image
Looking north-east
Large image
Looking west, at the 'polaraxis'.
Large image
Topview mount, fully opened.
Topview mount, fully closed.
Pay attention to the threaded rod. This rod rotates around it's axis(to do the actual tracking) but it also makes a rocking motion. The centre of this rocking motion is the lower bracket in which it is fixed. Both brackets have a rotating axis (bleu in the drawing) in which the threaded rods rotates.
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Chris
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jpcannavo
sage
Reged: 02/21/05
Posts: 324
Loc: Long Island New York
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Chris
This is a fiendishly clever design!!!
I have only two concerns:
1) The wooden glide blocks that compliment the hinge, completing the polar axis, could each be made as triangular blocks for rigidity.
2) The component of load parallel to the polar axis is partially born by the threaded rod. This might creates a fulcrum between the two glide blocks - potential for wobble.
Two identical threaded rod drive located at each glide block would overcomes this.
Otherwise very cool concept. Any working prototype?
Joe
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Joseph Cannavo
16" F5 Zambuto, front collimating, scope nearly complete - WSP here we come!
16" F5 Royce, conical blank, front collimating (Mirror Sold)
10" F5 Dob
Mid 70's RV-6
4" Orion 100mm ED
Mr Keeyoots (My Cat)
Edited by jpcannavo (08/08/08 07:49 AM)
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jdownie
professor emeritus
Reged: 02/24/06
Posts: 737
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The roots of the design go back to Haig's barndoor mount (1972).
Telescope Making had an article on a simpler version of the box mount in issue 14 (Winter 81/82) by Graeme White. Over the years there were several follow up articles and design variants.
John
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ATM project - a terrible waste of good Pyrex.
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Ed Jones
Pooh-Bah
Reged: 04/06/04
Posts: 1081
Loc: Sin-sin-atti
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Build it and report back. A design on paper may look great but the real test is to make it.
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Ed Jones
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Chriske
Kijkerbouw Urania
Reged: 08/15/04
Posts: 1953
Loc: Boechout, Belgium
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My first prototype I ever build was much higher, In fact to high to be practical. A 10" f/5 Dob on a 20" high mount. Have no more picture of it. You'll find some picture in a '83 S&T magazine. Don't know which month. I lost these magazine in a flood.
If someone could send me a scan of these pictures I would be very glad...
My idea to build this Boxmount came from Greame White. He proposed to use this mount for larger scopes in a magazine called 'Astronomy'. After having read the article in S&T Mr White asked me some picture to show him his idea realy did work, in a way he had some doubts himself.
I build a few others, each new one with more improvements. At the end I got it working very smooth. No backlash on the gliding blocks, very heavy scopes can be used with that airpump I mentioned higher up, and very transportable.
At first I had these triagles installed -in- the mount itself but I decided to mount these blocks outside the box to increase the distance to the hinge. The further these three points are sepparated the more stable the mount got. That's why I used these blocks, actually they're nothing more than planks in my last one.
I had lots of fun explaining people why that 'silly' thing actualy did work.
Most amateurs back then were all familiar with regular GEM, the Dob was strongly coming up, the first Equa. Platform was introduced : The Poncet mount. And there I was with my ugly looking box with a cheap hinge and a threaded rod telling all fellow ATM : hey look guys... this an Equ mount...!  Almost nobody believed me, until I started the RA motor.
This is the one I'm using right now.
Some parts a bit rusty, I know, but that's due to the flood I mentioned higher up. Unbelievable the electronics still work after all that water... 
Appart from the three threated rods (to adjust the mount on it's 3 concrete piers) this mount is about 6" high.
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Chris
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Chriske
Kijkerbouw Urania
Reged: 08/15/04
Posts: 1953
Loc: Boechout, Belgium
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Quote:
Build it and report back. A design on paper may look great but the real test is to make it.
Ed,
All the mounts I've posted so far in This thread : last post have been build before.
In the past there have been 'some' guys here on CN posting lots of 'paper' mounts and telescopes. I'm not one of them.
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Chris
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Wes James
Carpal Tunnel
Reged: 04/12/06
Posts: 2457
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Chris-
What is the angular relationship of the hinge at the angle of one's local latitude/polar axis- to the sliders/threaded rod on the opposite side- they're perpendicular to each other/opposed 90 degrees, correct? Also, how do you determine the shaft speed of the drive motor if you choose to use one?
Thanks again for all the work you're putting forth here... truly a wonderful body of work, worthy of being placed in the "Best Of" section under it's own folder of mount types. All your work is greatly appreciated by many of us out here!
Wes
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Chriske
Kijkerbouw Urania
Reged: 08/15/04
Posts: 1953
Loc: Boechout, Belgium
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Thanks Wess.... 
Correct 90° angular difference between rod and hinge, no matter what your latitude is.
Speed of the rod depends on the diameter of the threaded rod. I choose to use M10 as threaded rod so I had to search for the correct gearbox to lower the speed of the motor I'm using. The black thick 'wire' escaping at the lower part of threaded rod is actuualy a flexible steel cable about the same as used in bycicles for the breaks, only a bit thicker. It enters the mount through a small hole at the north of the mount. The fine-adjustment of the speed is done through electronics.
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Chris
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RossSackett
sage
Reged: 08/17/07
Posts: 338
Loc: Memphis, TN
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Chris:
Is an airpump the same thing as an automobile shock absorber (heavy loads) or cabinet airspring (light loads)?
Ross
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Ross Sackett
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11 scopes currently on the flight line from 4.25 to 18"; 5 pairs of astronomical binocs 35-80mm. My wife suggests that with just one pair of eyes, this might be excessive.
See my scope pix at http://www.flickr.com/photos/8315630@N04/
Carpe noctem!
Amateur astronomer = A mature moon-starer
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Chriske
Kijkerbouw Urania
Reged: 08/15/04
Posts: 1953
Loc: Boechout, Belgium
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Quote:
Chris:
Is an airpump the same thing as an automobile shock absorber (heavy loads) or cabinet airspring (light loads)?
Ross
Hi Ross,
Somewhere in between I suppose. I always use airpumps out of the rear doors of light trucks.
Congrat on the scope btw... 
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Chris
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Ed Jones
Pooh-Bah
Reged: 04/06/04
Posts: 1081
Loc: Sin-sin-atti
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So having made one would you evaluate it in terms of stability, overall height, easy of use etc compared to other designs. Why did you pick this design?
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Ed Jones
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Chriske
Kijkerbouw Urania
Reged: 08/15/04
Posts: 1953
Loc: Boechout, Belgium
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Quote:
So having made one would you evaluate it in terms of stability, overall height, easy of use etc compared to other designs. Why did you pick this design?
I just wanted a platform for my Dob. At the time (early 80s) there was no such thing as Equat. Platform as you (and all the others) build it these days. There was just the Poncet mount. I had to choose between that Poncet and the one I read about in Astronomy (White). It was just a very small drawing, just a few lines. I choose the difficult way and made a mount that never had been build before. I like the challenge, you should know by now Ed...
I still use it because I like the consept and it can handle very large scopes. But most of all it is very easy to build.
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Chris
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jdownie
professor emeritus
Reged: 02/24/06
Posts: 737
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Looks great Chris, and very timely, for me, with my plans to try a hinged escapement platform It was fascinating reading the White article and the follow-ons (nested box, etc.)
I take it the guides on the screw side remove some pressure for precision on the hinge?
I am not going to have the luxury of much width - 10" or so, so I am going to need all the help I can get.
John
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ATM project - a terrible waste of good Pyrex.
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Chriske
Kijkerbouw Urania
Reged: 08/15/04
Posts: 1953
Loc: Boechout, Belgium
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Quote:
Looks great Chris, and very timely, for me, with my plans to try a hinged escapement platform It was fascinating reading the White article and the follow-ons (nested box, etc.)
I take it the guides on the screw side remove some pressure for precision on the hinge?
I am not going to have the luxury of much width - 10" or so, so I am going to need all the help I can get.
John
John,
The guides are there to make the upperpart of the mount more stable. Without these two guides the upperpart of that mount would rest on just two points, not an ideal situation.
The airpump removes most of the pressure (in case of larger scopes)
The smallest boxmount I ever made was a box 25x25x20 cm. I installed my 90 mm Mak on it, serving as a guidescope to make pictures with my telephotolens. 20 min of tracking was no problem at all, no correction was needed during that timespan. For these little scopes no compensation for the scope's wheight is needed at all, so no airpump.
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Chris
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jdownie
professor emeritus
Reged: 02/24/06
Posts: 737
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Ah - the three points help with twist, for example?
Did you take 20 minute exposures, or is that more of a visual limit?
Thanks so much for posting this intriguing design execution.
John
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ATM project - a terrible waste of good Pyrex.
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Chriske
Kijkerbouw Urania
Reged: 08/15/04
Posts: 1953
Loc: Boechout, Belgium
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Quote:
Ah - the three points help with twist, for example?
Did you take 20 minute exposures, or is that more of a visual limit?
Thanks so much for posting this intriguing design execution.
John
The three point support helps prevent twisting of the mount. It gets rocksteady.
I indeed made a 20 minute (piggyback) exposure without even thoughing the telescope or mount. I think it is possible to take pictures through the scope itself, never tried it. In case of long exposers through the scope care must be taken the glidingblocks are perfectly straight to prevent uneven trackingmotion.
These 20 minutes are not the limit of that mount. It all depends on the construction of the mount. Mine can track up to 1.5 maybe 2 hours.
In case of longer exposure and longer focal lenght of the scope the tracking becomes critical and you will be forced to make a small RA correction from time to time. These corrections are exactly the same as with small a Barn-door tracking platform. With a Boxmount these tracking error will not have the same magnitude because of the larger distance between polaraxis and threaded rod.
The larger the platform, the smaller that tracking error gets.
If you want to build such a mount, let me know because not all (small) details are drawn in the 3D renderings. Otherwise it would take me days to finish one drawing.
Remember I only drew this mounts to have an overview of all possible mounts that could be made by amateurs. These drawings are absolutely no guide to build one.
Anyway I did not drew the lower connectionpoint of that threaded rod in detail, that is a very important one if you want to do some precisiontracking.
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Chris
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