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Equipment Discussions >> ATM, Optics and DIY Forum

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m31supernova
member


Reged: 09/04/09

Re: 16" F/1.2 Baker-Schmidt new [Re: Benach]
      #4240371 - 12/10/10 12:27 PM

Benach, nah I think it safe to trust others here that know a heck of alot about this stuff and assume I read something wrong. The mirror on astromart is obviousley the terabeam mirror due to the box saying "com" on it.

Paul, Info here: http://www.rfroyce.com/cassegrains.htm on Dall-Kirkham's suggest f ratio would need adjusting to +f/4. Would you make the convex secondary via treating it as the tool of a regular concave grind?
This Wiki link: http://en.wikipedia.org/wiki/Modified_Dall%E2%80%93Kirkham_telescope mentions modified Dall-Kirkham using focal corrector making them more suitable than RC's so sounds like a worthy project. Maybe following their reference link to the french site they sited will help. Another translation event: http://translate.google.com/#fr|en|


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nytecam
Postmaster


Reged: 08/20/05

Loc: London UK
Re: 16" F/1.2 Baker-Schmidt new [Re: kfrederick]
      #4240697 - 12/10/10 03:27 PM

Quote:

A lensless Schmidt


I've made a couple of Lensless Schmidt Cameras [see video link below] and the f/ratio, to produce acceptable images, has to be quite slow Most of this mirror's aperture would need to be stopped-down thus just adding unneccesary mass

For an Ebert spectrograph try my practical webpage

BTW the advertise knows his stuff IMHO


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Ruster
newbie


Reged: 11/25/10

Loc: Arizona, USA
Re: 16" F/1.2 Baker-Schmidt new [Re: nytecam]
      #4244271 - 12/12/10 01:52 PM

Terabeam was a startup Meade partnered with to develop inter-building gigabit optical datalinks. Sort of a solution without a problem once wireless got better. Meade did mod some 16" LX200 OTAs for this; interesting they're out in the marketplace now. The optics might have a tweaked (near-IR) coating.

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Owen
professor emeritus


Reged: 06/21/07

Loc: New Zealand
Re: 16" F/1.2 Baker-Schmidt new [Re: Ruster]
      #4247828 - 12/14/10 08:49 AM

From a rough calculation, you could make an optical train (ignoring SA), with this mirror using this acro from the shed, and a doublet from the shed.

such as
http://www.surplusshed.com/pages/item/l13003.html
and
http://www.surplusshed.com/pages/item/l2148.html

Basic calc indicates that the lens will revert the light cone back to infinity focussed (or very, very nearly), which you could use then to drive a much smaller scope.

Such a jury-rigged exercise demands low costs though, and I doubt that mirror is inexpensive...

Owen

Edited by Mike I. Jones (12/14/10 12:52 PM)


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Gene Hunter
sage
*****

Reged: 12/29/07

Loc: SC
Re: 16" F/1.2 Baker-Schmidt new [Re: Owen]
      #4536355 - 04/22/11 11:25 AM

I have this same mirror that I bought from ebay for $75 which I consider a fair price. I have not decided what to do with it yet, but I considered using just as a blank. I do know they where from the terabeam project which was to use light to communicate as it is safer than radio and microwaves which can be intercepted. I believe they where to communicate with satelites, and other secret stuff.

bought mine for when I get bored. one day I will do something with it. I did find someone who said they would make a corrector for it and from there I was thinking I would try one of those celestron fastar correctors to get a fast astrograph, but its a lot of money to just try something out.


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Flybywire
member
*****

Reged: 01/16/10

Re: 16" F/1.2 Baker-Schmidt new [Re: Gene Hunter]
      #4544484 - 04/26/11 12:57 AM

As I posted earlier in the thread, I also own one of these mirrors. I originally purchased it without any intention of using it for an optical application, however, now I am wondering if it would be feasible to build a scope with a sub-aperture corrector.

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richardteles
newbie


Reged: 02/01/13

Re: 16" F/1.2 Baker-Schmidt new [Re: Flybywire]
      #5677260 - 02/13/13 09:09 AM

HARD TO FIND PART TERABEAM USE FOR TELESCOPE

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ed_turco
Pooh-Bah
*****

Reged: 08/29/09

Loc: Lincoln, RI
Re: 16" F/1.2 Baker-Schmidt new [Re: Gordon Rayner]
      #5677445 - 02/13/13 11:01 AM

I saw one of these collimators at Wright-Patterson in 1962. It was 16" in diameter and the plate was a Schmidt corrector. As it was at the radius of curvature of the mirror, the dimensions seem right.

I was introduced to this by a Ph.D. Supervisor who explained the whole thing to me. His name was Pryor as I recall. It was quite the thing to test various lenses with this device and see what they could do!


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Geo.
Carpal Tunnel
*****

Reged: 10/01/08

Loc: Upstate NY
Re: 16" F/1.2 Baker-Schmidt new [Re: Benach]
      #5683150 - 02/16/13 10:22 AM Attachment (12 downloads)

Yes, the Terabeam contract makes sense. Guess laser communications have gone the way of the dodo.

Here are some notes from my files:

Optics (terabeam telescope)

Both Meade and Terabeam destroyed their files on these systems after they became obsolete. One surplus dealer was able to acquire these measurements:

The specs of the primary mirror as measured by a professional in optics manufacturing:

Pyrex Spherical Mirror by Meade - MSRP $2500

Speed = f/1.2
Spherical figure ~ ¼ wave Clear Aperture
Diameter = 16"Radius = 35"Bore = 4.25"
Pyrex cast blank (not sagged), avg. thickness = no less than .75"
Aluminum Coated with SIO overcoat
Ronchi test showed smooth parallel lines
Uniform .75" thickness allows for very quick temperature acclimation.

There are three ways to use this mirror for a telescope:

1) Use the primary only and find a company to build a schmit corrector plate (there are many)
2) Use the primary only and put a curved filmholder at the prime focus
3) Use the secondary mirror and the meniscus lens to render an image with negligible coma

To align the optics use a laser pointer and spread the beam into a line with a cylindrical lens. Align the primarywith the beam so that it sends the beam back upon itself then bolt on the secondary and adjust it so that the beam reflects in the same plane. A piece of tissue paper about 1" wide will make this easy. Repeat the process in the perpendicular plane by rotating the axis of the cylindrical lens 90 degrees

Don't attempt to test the optics over short distances as I was never able to obtain an image that way. Use the moon for initial testing as it's at infinity.
If you are new to telescope building I have one word of caution: Don't allow anything to ever contact the primary mirror, don't even try to clean the mirror. Use a can of compressed gas (Dust Off) but don't invert the can as it will spray liquid gas on the mirror and crack the aluminum coating due to thermal shearing.

Electronics(terabeam telescope)

The stepper motors included with the system are bipolar:

The steppers are manufactured by Lin engineering.

Wire Color Code:
Red -A
Blue- A'
Green - B
Black - B'

Lin Engineering wiring page www.linengineering.com/our_products/wiringcon.htm


The Included gearboxes are manufactured by Harmonic Drive.

Here's how it works:
The teeth on the non-rigid Flexspline and the rigid Circular Spline are in continuous engagement. Since the Flexspline has two teeth fewer than the Circular Spline, one revolution of the input causes relative motion between the Flexspline and the Circular Spline equal to two teeth. With the Circular Spline rotationally fixed, the Flexspline rotates in the opposite direction to the input at a reduction ratio equal to one-half the number of teeth on the Flexspline.


Edited by Geo. (02/16/13 10:40 AM)


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Ed Jones
Carpal Tunnel
*****

Reged: 04/06/04

Loc: Sin-sin-atti
Re: 16" F/1.2 Baker-Schmidt new [Re: Geo.]
      #5683578 - 02/16/13 01:56 PM Attachment (12 downloads)

Here's one idea but uses only 14 inches of it. The oblate R2 would be a challenge.

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Larry Silvestri
member


Reged: 01/29/13

Re: 16" F/1.2 Baker-Schmidt new [Re: Ed Jones]
      #5683640 - 02/16/13 02:29 PM

It would make a nice Hindle sphere.

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