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mark cowan
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Trends, future trends, and "should be dones"...
      #5320447 - 07/16/12 02:06 PM

Hi,

I was about to post this in the "tests" thread but thought it would better stand as a new thread about ways to improve performance...

This is by no means a complete list - let's hear some others!



A short list of trends, future trends, and "should be dones" in no particular order:
  • Something that could help a great deal in amateur scopes but isn't really here yet is adaptive optics. Technology is willing but the price is still a bit high.
  • Ultra-thin mirrors leading to superb thermal performance (though this needs to apply to secondaries as well at some point).
  • A fairly well established trend is stepless alt-az drives for large dobs that keep objects centered at high power allowing full utilization of those moments of clarity.
  • Baffling done right - at the focuser base, at the OTA opposite the focuser, at the entrance pupil (the upper cage or ring), at the mirror (to block light from the ground). With baffling done right even open trusses without shrouds are impervious to glare, and glare is a killer for contrast.
  • Speaking of shrouds, making them from a material (such as sail cloth with Mylar film) with a thermal barrier could help a lot in isolating the heat plumes from observers.
  • Better collimation, including commercial structures that hold collimation right out of the box.
  • Seen at Oregon Star Party - observer shrouds, baffles that go over your head or at least reduce incident glare to the eye itself.

Best,
Mark


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cheapersleeper
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Re: Trends, future trends, and "should be dones"... new [Re: mark cowan]
      #5320485 - 07/16/12 02:25 PM

" Speaking of shrouds, making them from a material (such as sail cloth with Mylar film) with a thermal barrier could help a lot in isolating the heat plumes from observers. "

If this was done, I might build a truss rod beastie.


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jwaldo
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Loc: Simi Valley, CA
Re: Trends, future trends, and "should be dones"... new [Re: cheapersleeper]
      #5320495 - 07/16/12 02:32 PM

The deeper down the Dobsonian rabbit hole I go, the more I feel that bearing materials and design could be demystified a bit. It's on my to-do list.

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Benach
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Re: Trends, future trends, and "should be dones"... new [Re: jwaldo]
      #5320501 - 07/16/12 02:33 PM

"Better collimation, including commercial structures that hold collimation right out of the box."

These exist already for 100+ years.


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RossSackett
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Re: Trends, future trends, and "should be dones"... new [Re: Benach]
      #5320510 - 07/16/12 02:39 PM

Right on, Mark.

I'd add better mobility solutions (easy wheels) and more comfortable scope ergonomics.


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Dick Jacobson
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Loc: Plymouth, Minnesota, USA
Re: Trends, future trends, and "should be dones"... new [Re: RossSackett]
      #5320675 - 07/16/12 04:26 PM

Eyepieces or focusers with built-in anti-dew heaters.

Gas-cylinder adjustable chairs with a wide height range.

Tubes with built-in lazy Susan type rotation rings.


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MitchAlsup
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Re: Trends, future trends, and "should be dones"... new [Re: mark cowan]
      #5320767 - 07/16/12 05:29 PM

Quote:

  • Baffling done right - at the focuser base, at the OTA opposite the focuser, at the entrance pupil (the upper cage or ring), at the mirror (to block light from the ground). With baffling done right even open trusses without shrouds are impervious to glare, and glare is a killer for contrast.




  • Minor quibble: Unshrouded with correct baffling: the image plane is impervious to direct illumination by stray light, but not impervious to ligh shining on said baffle and that the emission of light from the baffle can reach the image plane.


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    kfrederick
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    Re: Trends, future trends, and "should be dones"... new [Re: MitchAlsup]
          #5320788 - 07/16/12 05:45 PM

    Bigger and faster with thin mirrors .

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    NHRob
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    Re: Trends, future trends, and "should be dones"... new [Re: kfrederick]
          #5321061 - 07/16/12 09:15 PM

    focuser with integrated adjustable iris (or as an attachment option), much like a camera iris. For optimizing focuser baffling.

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    RossSackett
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    Re: Trends, future trends, and "should be dones"... new [Re: NHRob]
          #5321108 - 07/16/12 10:19 PM

    CNC templets for milling wooden scope parts

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    mark cowan
    Vendor (Veritas Optics)
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    Re: Trends, future trends, and "should be dones"... new [Re: Dick Jacobson]
          #5325966 - 07/19/12 10:38 PM


    Quote:

    Gas-cylinder adjustable chairs with a wide height range.




    I've seen some cool chair designs. And just got a "zero-gravity" reclining lawn chair, it looks like there's some good mounting points on it for a simple binoc holder. Though that's not a dob thing.

    Quote:

    focuser with integrated adjustable iris (or as an attachment option), much like a camera iris. For optimizing focuser baffling.




    Or exactly like a camera iris. I have one that's not-quite-big enough, and I sent a twin of it off to another CNer for their use.

    Quote:

    Bigger and faster with thin mirrors .




    I hope that goes without saying...

    Quote:

    Minor quibble: Unshrouded with correct baffling: the image plane is impervious to direct illumination by stray light, but not impervious to ligh shining on said baffle and that the emission of light from the baffle can reach the image plane




    Uhm, yes. So, add nanocarbon forest material for ultimate light trapping in baffle material.

    Best,
    Mark


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    EyeSage
    super member


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    Re: Trends, future trends, and "should be dones"... new [Re: mark cowan]
          #5326167 - 07/20/12 12:42 AM

    Quote:

    • Seen at Oregon Star Party - observer shrouds, baffles that go over your head or at least reduce incident glare to the eye itself.






    Amazing an idea that's been around this long is a new idea to astronomers, appearing on a list of future trends alongside adaptive optics .



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    Dick Jacobson
    scholastic sledgehammer


    Reged: 12/22/06

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    Re: Trends, future trends, and "should be dones"... new [Re: mark cowan]
          #5326317 - 07/20/12 04:54 AM

    Quote:

    Seen at Oregon Star Party - observer shrouds, baffles that go over your head or at least reduce incident glare to the eye itself.



    See Observing Canopy and Observing Vest. I have both and they both work well. I haven't tried a stovepipe hat, though.


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    Pinbout
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    Re: Trends, future trends, and "should be dones"... new [Re: EyeSage]
          #5327713 - 07/21/12 12:46 AM

    Quote:

    Amazing an idea that's been around this long is a new idea to astronomers, appearing on a list of future trends alongside adaptive optics .





    yeah, I recently went to look for my dark cloth that was suppose to be packed away with my sinar f1 but it wasn't in the case.


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    PierreDesvaux
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    Re: Trends, future trends, and "should be dones"... new [Re: Pinbout]
          #5327802 - 07/21/12 04:05 AM

    Nice list!

    I would add:

    - Ultralightweight scopes with thin mirrors and carbone structures. For instance, a 16" dob weighting not more than 20 pounds (already done).

    - Focusser with integrated filterslider or filterbox.

    - Lightweight Ethos-like eyepieces.

    - Improved push-to pointing accuracy using an i-phone

    - Anti-due optics coating,

    - Automated collimation using an i-phone

    The sky is the limit...


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    kfrederick
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    Re: Trends, future trends, and "should be dones"... new [Re: PierreDesvaux]
          #5327843 - 07/21/12 06:45 AM

    There are new computer designed Telescopes . Like the Shief /Chief/ Yolos/ have been optimized . Great for ATMs to try as lots of help on this forum like ED , Mike ,Dave .

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    haywool
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    Re: Trends, future trends, and "should be dones"... new [Re: kfrederick]
          #5327856 - 07/21/12 07:28 AM

    What about a pair of simple, lightweight eyeglasses that allow a detailed view of our most distant stars and galaxies ... with optional filters for solar gazing ??

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    Jon Isaacs
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    Re: Trends, future trends, and "should be dones"... new [Re: PierreDesvaux]
          #5327861 - 07/21/12 07:34 AM

    The smart phone with gyros is here and promises to make accurate cellphone and tablet based DSCs a reality. This is not far away.

    Of course a smart phone, by the time the contract is finished costs as much as a Sky Commander.

    Jon


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    Pinbout
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    Re: Trends, future trends, and "should be dones"... new [Re: PierreDesvaux]
          #5327915 - 07/21/12 08:54 AM

    Quote:

    - Ultralightweight scopes with thin mirrors and carbone structures. For instance, a 16" dob weighting not more than 20 pounds (already done).





    I don't know about thinner but lighter yes

    Normand Fullum's sandwich


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    Jeff Morgan
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    Re: Trends, future trends, and "should be dones"... new [Re: mark cowan]
          #5328074 - 07/21/12 11:11 AM

    A substrate that can take a polish like glass, weighs as much as carbon fiber, and rigid enough to hold shape without an elaborate cell.

    The mirror and the cell are to the two highest density/highest weight components in telescopes. Find a substrate to replace glass and then eliminate the cell - that would be game-changer.


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    tim53
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    Re: Trends, future trends, and "should be dones"... new [Re: Jeff Morgan]
          #5328109 - 07/21/12 11:35 AM

    Suspend a monolayer of aluminum in a tuned magnetic field?

    -Tim.


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    tim53
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    Re: Trends, future trends, and "should be dones"... new [Re: Jeff Morgan]
          #5328110 - 07/21/12 11:36 AM

    But my wish for a near-future trend would be inexpensive, intensified CCD cameras.

    -Tim.


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    careysub
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    Re: Trends, future trends, and "should be dones"... new [Re: Jeff Morgan]
          #5328201 - 07/21/12 12:33 PM

    Quote:

    A substrate that can take a polish like glass, weighs as much as carbon fiber, and rigid enough to hold shape without an elaborate cell.

    The mirror and the cell are to the two highest density/highest weight components in telescopes. Find a substrate to replace glass and then eliminate the cell - that would be game-changer.




    Hmmm... not sure the material you describe would be as big a breakthrough as you might think. The key parameter here is "specific stiffness", the ratio of modulus to density. Using the units employed by Table 6 from "The design and construction of large optical telescopes", (p. 139, 2003), which are GPa/(kg/m^3), the stiffness of Pyrex is 0.032 and Zerodur is 0.036, while bi-directional carbon fiber/epoxy specimens range from about 0.040 to 0.055 depending on details of manufacture. This is an improvement on the order of 50% (Pyrex to mid-range CF, or Zerodur to top performing CF), which would help but not really be a radical game changer by itself. (The book has the two extremely costly exotics silicon carbide and beryllium holding pride of the show at 0.146 and 0.162).

    Now what would be more radical is if it were economical to get away from the constraints of a homogeneous flat mirror - meniscus mirrors, hollow core, foam core, ribbed mirrors, or other designs that create hollow frames of some sort. Could a composite type of mirror substrate help there?

    I would say the Hubble Optics has made a stab in that direction with their low-cost sandwich mirrors, though their sandwich technique is fairly crude. There is quite a thick forest of glass columns on the two halves of the mirror blank, which in my mirror don't match up very well - I think it is over-designed using extra material to substitute for finesse, a more careful process should be able to get much better weight savings.

    And there is that StarStone project out there working on foamed mirrors. They say they are shipping 18" and 24" blanks and "light bucket" (worse than 1/4 wave) mirrors - has anyone seen one of these?

    And on point 2 - the cell. What is a typical cell weight to mirror weight ratio? You can of course make a cell arbitrarily heavy if you like, but it seems to me that the cell need not be more than a fraction of the weight of the mirror since it is free to use its materials in a more efficiently stiff structure than the flat mirror (i.e. it should already have the structure we would like in an advanced mirror blank). An advanced mirror might do away with the need of a sophisticated cell, but the cell shouldn't be a big weight driver compared to the mirror itself.

    What is the flexure tolerance in the cell anyway? It provides floating support points, which are designed to inherently adjust to distribute the load. The main problem would be collimation shift due to rotation of the support plane (and the mirror) relative to the secondary as the altitude changes, and only uneven changes in cell flex would cause this. Am I thinking about this correctly?


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    Jon Isaacs
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    Re: Trends, future trends, and "should be dones"... new [Re: careysub]
          #5328280 - 07/21/12 01:16 PM

    Quote:

    Hmmm... not sure the material you describe would be as big a breakthrough as you might think. The key parameter here is "specific stiffness", the ratio of modulus to density. Using the units employed by Table 6 from "The design and construction of large optical telescopes", (p. 139, 2003), which are GPa/(kg/m^3), the stiffness of Pyrex is 0.032 and Zerodur is 0.036, while bi-directional carbon fiber/epoxy specimens range from about 0.040 to 0.055 depending on details of manufacture. This is an improvement on the order of 50% (Pyrex to mid-range CF, or Zerodur to top performing CF), which would help but not really be a radical game changer by itself. (The book has the two extremely costly exotics silicon carbide and beryllium holding pride of the show at 0.146 and 0.162).





    While the specific stiffness would allow for a lighter mirror, these are not the material properties which make glass and similar materials desirable as materials for mirrors. Composites inherently inhomogeneous and on a micro/nano scale have thermal CTE issues.

    Jon


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    careysub
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    Re: Trends, future trends, and "should be dones"... new [Re: Jon Isaacs]
          #5328460 - 07/21/12 03:43 PM

    Quote:

    Quote:

    Hmmm... not sure the material you describe would be as big a breakthrough as you might think. The key parameter here is "specific stiffness", the ratio of modulus to density. Using the units employed by Table 6 from "The design and construction of large optical telescopes", (p. 139, 2003), which are GPa/(kg/m^3), the stiffness of Pyrex is 0.032 and Zerodur is 0.036, while bi-directional carbon fiber/epoxy specimens range from about 0.040 to 0.055 depending on details of manufacture. This is an improvement on the order of 50% (Pyrex to mid-range CF, or Zerodur to top performing CF), which would help but not really be a radical game changer by itself. (The book has the two extremely costly exotics silicon carbide and beryllium holding pride of the show at 0.146 and 0.162).





    While the specific stiffness would allow for a lighter mirror, these are not the material properties which make glass and similar materials desirable as materials for mirrors. Composites inherently inhomogeneous and on a micro/nano scale have thermal CTE issues.

    Jon




    Density and stiffness were the properties that Jeff Morgan cited though.

    The "The design and construction of large optical telescopes" has a different figure of merit it uses to compare the best mirror materials - the thermal conductivity divided by the product of the specific heat, density (these two together are obviously the heat capacity per volume) and the coefficient of thermal expansion. By this figure of merit the best materials they rated were (in descending order): SiC, ULE (ultra-low expansion fused quartz), and Zerodur with everything else much farther back.

    Curiously Zerodur (Astrosital, etc.) get their superior properties of zero thermal expansion because of nano-scale inhomogeneities, mixtures of different crystal structures, carefully tailored of course.


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    Jon Isaacs
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    Re: Trends, future trends, and "should be dones"... new [Re: careysub]
          #5330446 - 07/22/12 09:23 PM

    Quote:

    Density and stiffness were the properties that Jeff Morgan cited though.




    This is what Jeff wrote:

    "A substrate that can take a polish like glass, weighs as much as carbon fiber, and rigid enough to hold shape without an elaborate cell."

    My point is simply that stiffness and density are important properties but are not sufficient for choosing a material. As Jeff said, "take polish like glass" and one would include thermal stability and homogeneity among others... That doesn't sound like any fiber composite I know of...

    Jon


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    tim53
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    Re: Trends, future trends, and "should be dones"... new [Re: Jon Isaacs]
          #5330724 - 07/23/12 01:07 AM

    Hm...

    Why not spin cast "float glass" mirrors?: Float molten glass on molten tin, but spin it. When it cools, you've got a thin parabola.

    -Tim.


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    mark cowan
    Vendor (Veritas Optics)
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    Re: Trends, future trends, and "should be dones"... new [Re: EyeSage]
          #5331602 - 07/23/12 04:02 PM

    Quote:

    Amazing an idea that's been around this long is a new idea to astronomers, appearing on a list of future trends alongside adaptive optics .






    Indeed it is, using a dark shroud over your head in the dark - who'da thunk it?

    Well, not many people, 'cause it caught on rapidly once first "observed".

    Quote:

    Why not spin cast "float glass" mirrors?: Float molten glass on molten tin, but spin it. When it cools, you've got a thin parabola.




    I catch enough grief for molten pitch as it is. But though this sounds good and might get you in the outfield, the difference in density between the tin and the glass is going to result in a different shape on the glass...

    Plus, well, the tin isn't hot enough to keep the glass molten, in making float glass the oven extrudes a layer onto the tin bath, where it floats, cools, and hardens.

    Quote:

    - Lightweight Ethos-like eyepieces.




    +1. I would also like to see lightweight optical finders.

    The use of carbon fiber and composites in telescope design will only grow.

    Quote:

    The mirror and the cell are to the two highest density/highest weight components in telescopes. Find a substrate to replace glass and then eliminate the cell - that would be game-changer.




    Yes, but I'm now exploring ultra-thin fast mirrors (meniscus). And I have a very lightweight "fractal" cell design to support them (which I may patent).

    But once you take that much weight away (talking a sub 4 lb 14.7" f/3 quartz mirror) even a recognizable ultralight dob design will never balance without adding counterweights (which unless they serve some other function like batteries I'd like to avoid). Fast f/ratios help here, but I'm still trying to crack a design barrier (and yes, double truss is nice...).

    Quote:

    ...foamed mirrors...18"...has anyone seen one of these?




    Have worked with one such blank.

    Best,
    Mark


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    Starman1
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    Re: Trends, future trends, and "should be dones"... new [Re: mark cowan]
          #5331653 - 07/23/12 04:27 PM

    Carbon fiber EQ and AZ mounts with carbon fiber tripods. Lightness of weight, yet super-high stiffness if constructed correctly for the material used. They may not look the same as the mounts we currently use.

    Dobsonians with honeycomb-core carbon fiber rocker boxes and mirror boxes, carbon fiber poles and carbon fiber UTAs.

    Secondary holders fine-adjustable with thumb screws in multiple dimensions: back-and-forth away from the focuser, up and down the tube, rotation along a center axis, and tilt in at least two axes.

    Secondary spiders capable of accepting such high tension, and stiff enough, that 4-6" secondaries won't even move 0.001" over a full 90 degrees of altitude motion in the scope. We may have to re-think the way spiders are built and attached to do this.

    Ultralight scopes designed to have the same amount of stiffness as a regular-weight scope.


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    mark cowan
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    Re: Trends, future trends, and "should be dones"... new [Re: Starman1]
          #5331668 - 07/23/12 04:34 PM


    Quote:

    Ultralight scopes designed to have the same amount of stiffness as a regular-weight scope.




    Or simply better geometry (design) so forces are carried over shortest possible distances, allowing stiffness to be put to best use.

    Ditto for spiders, I have a wire design that doesn't rely on tension for its stability. Hasn't been tested at large sizes yet, but a few people have built this so far.

    Best,
    Mark


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    Pinbout
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    Re: Trends, future trends, and "should be dones"... new [Re: mark cowan]
          #5331711 - 07/23/12 04:50 PM

    i'd rather see my scope self-collimate.

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    tim53
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    Re: Trends, future trends, and "should be dones"... new [Re: mark cowan]
          #5331971 - 07/23/12 07:37 PM

    Quote:


    Quote:

    Why not spin cast "float glass" mirrors?: Float molten glass on molten tin, but spin it. When it cools, you've got a thin parabola.




    I catch enough grief for molten pitch as it is. But though this sounds good and might get you in the outfield, the difference in density between the tin and the glass is going to result in a different shape on the glass...




    I don't think the density has anything to do with the shape: rotating furnaces link

    Quote:

    Plus, well, the tin isn't hot enough to keep the glass molten,




    Precisely why it works - the tin is still molten when the glass has hardened.

    Quote:

    in making float glass the oven extrudes a layer onto the tin bath, where it floats, cools, and hardens.




    Not so. The glass is melted at 1600C and floats, as a liquid, on the tin bath: Float glass manufacture




    So, I'm envisioning something of a cross between the float glass manufacturing process and the Mirror Lab's spin casting process, whereby a rotating furnace with glass floating on a tin bath is rotated to produce a disk that has matching parabolas on its top and bottom surfaces and is, say, 1" thick and a meter in diameter, and only requires figuring. Well, that and mounting in a suitable cell! ...which is then mounted in a computer-controlled telescope in my observatory!

    -Tim.


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    Jeff Morgan
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    Re: Trends, future trends, and "should be dones"... new [Re: mark cowan]
          #5332070 - 07/23/12 08:49 PM

    Quote:

    But once you take that much weight away (talking a sub 4 lb 14.7" f/3 quartz mirror) even a recognizable ultralight dob design will never balance without adding counterweights (which unless they serve some other function like batteries I'd like to avoid). Fast f/ratios help here, but I'm still trying to crack a design barrier (and yes, double truss is nice...).





    Well if you could get the mirror that light ... why not add the counterweights forward of the diagonal mirror (as in a Springfield Newtonian) to raise the center of gravity coincident with the diagonal mirror. Say, 36"-40" off the ground. That would allow for a fixed height eyepiece at a normal sitting position. The only moving the observer would have to do would be in azimuth, and eyepiece weight would be negated.


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    RobDob
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    Re: Trends, future trends, and "should be dones"... new [Re: Jeff Morgan]
          #5332175 - 07/23/12 09:49 PM

    Like the VLA, A network of CCD imagers spread around thousands of miles all taking an image at the same time, a central computer would use software to interpolate (fill in the gaps without the need for optics), thus generating the images from spaces between the CCD imagers, then combine some zillion images into one (accounting for location, parallax, distance, etc). You now have ~3000 mile aperture telescope! Think of the 3D effect from something like that!...

    Edit: Big flaw here, would need a large portion of the earth to not have cloudy skies. Yikes! Oh well, maybe scale it down to 100 miles, or better yet, postion the CCD array around the clouds?

    Another edit: Nevermind, I think this exceeds the realm of ATM

    Rob

    Edited by RobDob (07/23/12 10:30 PM)


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    tim53
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    Re: Trends, future trends, and "should be dones"... new [Re: RobDob]
          #5332354 - 07/23/12 11:50 PM

    You could do that with just 2 telescopes, one on either side of the globe, pointing at the same object at the same time and looking at the same wavefront at the same time. Of course, it'd likely be day at one telescope if it's night at the other!

    -Tim.


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    RobDob
    sage


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    Re: Trends, future trends, and "should be dones"... new [Re: tim53]
          #5332423 - 07/24/12 12:44 AM

    Yeah Tim, it would be a logistical nightmare.

    Thinking more about this, the sum of a gillion small aperture CCD's would still not yield a very large (in the order of many miles across) aperture. It would just be a collective of small aperture CCD's added together...

    Oh well, it was fun to think about...

    Rob


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    tezster
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    Re: Trends, future trends, and "should be dones"... new [Re: Starman1]
          #5332670 - 07/24/12 08:26 AM

    Quote:

    Carbon fiber EQ and AZ mounts with carbon fiber tripods. Lightness of weight, yet super-high stiffness if constructed correctly for the material used. They may not look the same as the mounts we currently use.

    [snip]

    Dobsonians with honeycomb-core carbon fiber rocker boxes and mirror boxes, carbon fiber poles and carbon fiber UTAs.





    Being someone who's obsessed with telescope weight, these ideas sound fantastic to me, although it sounds quite expensive to implement.


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    Dick Jacobson
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    Re: Trends, future trends, and "should be dones"... new [Re: Starman1]
          #5332725 - 07/24/12 09:06 AM

    Quote:

    Secondary spiders capable of accepting such high tension, and stiff enough, that 4-6" secondaries won't even move 0.001" over a full 90 degrees of altitude motion in the scope. We may have to re-think the way spiders are built and attached to do this.



    How about using two spiders side-by-side, with a sufficiently strong rod connecting them and the secondary holder?


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    Dick Jacobson
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    Re: Trends, future trends, and "should be dones"... new [Re: RobDob]
          #5332738 - 07/24/12 09:15 AM

    See Hypertelescope for a proposal for an optical telescope larger than the Earth. Not exactly an ATM project, at least in this century.

    Another mega-telescope idea is to send an array of detectors out to 550 A.U. and use the Sun's gravitational field as a lens.


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    PierreDesvaux
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    Re: Trends, future trends, and "should be dones"... new [Re: Dick Jacobson]
          #5333215 - 07/24/12 02:35 PM

    Serge Vieillard made a few years ago an ultra-light 16" dobson with carbon composite: The weight of the structure is around 8 pounds, and the primary mirror 22 pounds.
    He goes to Chile, Namibia, or Sahara desert with it.


    http://www.astrosurf.com/magnitude78/T400/index.html

    Concerning the question of balancing the scope when using an ultralight primary mirror, I wonder what coud be done using powerfull magnets between the sidebearings and the rocker. The magnets should not be in direct contact with the side-bearings, in order to avoid any stinction effect ... Did anybody try this ?

    Concerning the ultralight mirrors, there are researches by amateurs on the principle of a thin layer of glass glued to a thick carbon foam. The carbon foam is very light and very rigid.


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    Re: Trends, future trends, and "should be dones"... new [Re: Jeff Morgan]
          #5333238 - 07/24/12 02:50 PM

    Quote:

    i'd rather see my scope self-collimate.




    Well, all-spherical designs are self-collimating.

    @Tim:
    Quote:

    I don't think the density has anything to do with the shape: rotating furnaces link




    Ah, you're right - the mass of the liquids cancel out - if one is heavier it's also gaining more kinetic energy from being spun.

    Quote:

    Not so. The glass is melted at 1600C and floats, as a liquid, on the tin bath: Float glass manufacture




    Indeed so. Look around 4 minutes into the video, "the glass leaves the furnace and passes onto the molten tin. Tin melts at 232C and glass at 1600C, although you could hit the tin up hot enough to melt the glass (it boils at 2600C) that's not how they melt the glass.

    Quote:

    So, I'm envisioning something of a cross between the float glass manufacturing process and the Mirror Lab's spin casting process, whereby a rotating furnace with glass floating on a tin bath is rotated to produce a disk that has matching parabolas on its top and bottom surfaces and is, say, 1" thick and a meter in diameter, and only requires figuring. Well, that and mounting in a suitable cell! ...which is then mounted in a computer-controlled telescope in my observatory!




    But this doesn't work - the surface of the resultant glass paraboloid is only close, it still requires machining, grinding, and figuring. Look further down that Wiki article on rotating furnaces.

    Besides, you'd need to run the incandescent thing through actual annealing cycles while keeping it running. I can slump a 1m piece of 1" glass in an annealing oven on a form much more easily, and get the same result.

    Anyway, the difference between paraboloid and spherical (for the bottom side anyway) is mostly trivial...

    @Jeff:
    Quote:

    Well if you could get the mirror that light ... why not add the counterweights forward of the diagonal mirror (as in a Springfield Newtonian) to raise the center of gravity coincident with the diagonal mirror. Say, 36"-40" off the ground. That would allow for a fixed height eyepiece at a normal sitting position. The only moving the observer would have to do would be in azimuth, and eyepiece weight would be negated.




    Indeed, that was one of the possibilities I've considered. But for the demonstration version (that just has to work) I'm going with a tube and a tall foam/veneer modular rocker box. It'll still look like a Springfield mount a bit as the short portion of the tube is in the front, focuser (SIPS) + EP + finders outweigh the mirror.

    @RobDob:
    Quote:

    Like the VLA, A network of CCD imagers spread around thousands of miles all taking an image at the same time, a central computer would use software to interpolate (fill in the gaps without the need for optics), thus generating the images from spaces between the CCD imagers, then combine some zillion images into one (accounting for location, parallax, distance, etc). You now have ~3000 mile aperture telescope! Think of the 3D effect from something like that!...




    Not gonna work, as phase is lost once you make those images. All you'd have is the same as combining a whole bunch of images from one telescope, and you can already do that easily.


    @PierreDesvaux:
    Quote:

    Concerning the question of balancing the scope when using an ultralight primary mirror, I wonder what coud be done using powerfull magnets between the sidebearings and the rocker. The magnets should not be in direct contact with the side-bearings, in order to avoid any stinction effect ... Did anybody try this ?




    It may be possible to use a drive system to supply the forces of a counterweight, and thus overcome inherent out-of-balance loads - as well as to compensate for wind loading on ultralight structures. But I haven't worked out what kind of power requirements this would take yet, though cogging motors might help (usually a bad idea in telescope drives).

    Best,
    Mark

    Edited by mark cowan (07/24/12 02:56 PM)


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    PierreDesvaux
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    Re: Trends, future trends, and "should be dones"... new [Re: mark cowan]
          #5333267 - 07/24/12 03:13 PM

    I forgot something: a strong, rigid and ligthweight focuser, made with carbone composite. Also easily feasible.

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    tim53
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    Re: Trends, future trends, and "should be dones"... new [Re: PierreDesvaux]
          #5333869 - 07/24/12 09:51 PM

    Quote:

    Quote:

    So, I'm envisioning something of a cross between the float glass manufacturing process and the Mirror Lab's spin casting process, whereby a rotating furnace with glass floating on a tin bath is rotated to produce a disk that has matching parabolas on its top and bottom surfaces and is, say, 1" thick and a meter in diameter, and only requires figuring. Well, that and mounting in a suitable cell! ...which is then mounted in a computer-controlled telescope in my observatory!






    But this doesn't work - the surface of the resultant glass paraboloid is only close, it still requires machining, grinding, and figuring. Look further down that Wiki article on rotating furnaces.




    If the glass is truly liquid when in the rotating furnace, it should be possible to produce a perfect parabola, similar to how mercury mirrors are "made" and used. I would imagine that the annealing process might change the shape away from a perfect figure, though, so some grinding and polishing would probably be needed. And of course, the spinning furnace wouldn't be a trivial thing to make or control at such high temperatures. So, I suspect such a specialized process is unlikely to take hold in such a small market for that sort of thing.

    -Tim.


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    RobDob
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    Re: Trends, future trends, and "should be dones"... new [Re: tim53]
          #5334036 - 07/25/12 12:04 AM

    "Not gonna work, as phase is lost once you make those images. All you'd have is the same as combining a whole bunch of images from one telescope, and you can already do that easily".

    I get that, but maybe phase can be modelled? (Edit: we're within the electromagnetic spectrum, they've done this with radio waves, why not with light?) Example: Let's take a 10ft. circle. Put 10 CCD imagers in that circle, capturing the images of each chunk of the circle. So, now we have a 10 ft. aperture database of light captured.

    Model that captured light database into a software based telescope, hey choose any focal ratio...

    Yeah, I know easier said than done, just having fun thinking about this, and we are talking about the future, right?

    Rob

    Edited by RobDob (07/25/12 12:15 AM)


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    highfnum
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    Re: Trends, future trends, and "should be dones"... new [Re: RobDob]
          #5334472 - 07/25/12 10:42 AM

    Holographic lens at least for solar eyepiece

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    Re: Trends, future trends, and "should be dones"... new [Re: highfnum]
          #5334675 - 07/25/12 12:22 PM

    What about a secondary mirror suspended by powerful magnets. This would knock out diffraction from the spider. Though most would probably fear a magnet failing with the secondary plunging to your primary mirrors death.

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    Nils Olof Carlin
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    Re: Trends, future trends, and "should be dones"... new [Re: Pinbout]
          #5334789 - 07/25/12 01:16 PM

    Quote:

    i'd rather see my scope self-collimate.


    Should be doable with good old technology, methinks:
    put an IR emitting diode one side of the focuser, casting a shadow of the center marker on the oposite side. And put 3 IR photodiodes there, in a triangle, straddling the edge of the shadow when the primary is collimated. Any miscollimation of the primary will unbalance the diode outputs. Feed the signals difference to servos on 2 of the collimation bolts.
    You could run it all the time, or just once per new object (and between exposures!)
    (Collimation of the focuser axis is by no means as critical)

    Nils Olof


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    Pinbout
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    Re: Trends, future trends, and "should be dones"... new [Re: Nils Olof Carlin]
          #5334881 - 07/25/12 01:50 PM

    Quote:

    You could run it all the time, or just once per new object




    that was my thinking. they could be in a closed loop including the secondary.

    I thought about when I run a series of timing relays in a closed loop and they all start switch till they get in line.


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    mark cowan
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    Re: Trends, future trends, and "should be dones"... new [Re: tim53]
          #5334955 - 07/25/12 02:25 PM

    Quote:

    If the glass is truly liquid when in the rotating furnace, it should be possible to produce a perfect parabola, similar to how mercury mirrors are "made" and used.




    You're neglecting surface tension (which is considerable with glass and changes with temperature), inhomogeneities in the glass, and the simple bit, which is that it takes a very long time both to melt the glass (like in the UofA Glass Lab) and even at that melt temp it's not really truly liquid, more like thick molasses. Glass at temps where it pours freely is entering another realm altogether, SFAIK, and I don't know much about how it behaves, but IIRC it begins to degrade at those temps, vitrifies, the chemistry gets out of hand.

    In any case as you cool it down and it thickens it will contract from the edges (the surface tension). Look at this picture which shows Supramax sheets coming off the Schott rolling line - the edges are all rounded, and this stuff was extruded through massive rollers just to shape it as flat as it is.

    I like the idea though, don't get me wrong! I just think it won't work in practice for the reasons I gave.

    Best,
    Mark


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    Re: Trends, future trends, and "should be dones"... new [Re: RobDob]
          #5334986 - 07/25/12 02:44 PM

    Quote:

    I get that, but maybe phase can be modelled?




    No, you need optical interferometry to do this over a wide space.

    Quote:

    we're within the electromagnetic spectrum, they've done this with radio waves, why not with light?




    OK, I'll tell ya why. Radio wavelength interferometry is possible electronically because you can capture the full EM information in the much larger waves (e.g. slower frequency, for instance the 21cm band is 1420MHz). The frequency of light is around 600THz (400,000 times higher, well beyond current technology in terms of digitization). So as far as a "future trend" you're gonna have to wait for purely optical (or molecular) computers to even begin to address it, and a data pipe bigger than God to connect the pieces together, but other than that, sure, and thanks for suggesting it.

    For where it has been done optically, see the Wiki. Takes a lot of very accurate tech to pull this off at all. Keck closed their program recently, it was just too iffy IIRC.

    Best,
    Mark


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    mark cowan
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    Re: Trends, future trends, and "should be dones"... new [Re: highfnum]
          #5334999 - 07/25/12 02:50 PM

    Quote:

    Holographic lens at least for solar eyepiece




    Indeed. The application of nano optical patterns (flat refractive elements) might help make ultralight EPs possible sooner than we think, too (this is only remotely feasible for small elements today). And I wonder why patterned diffractive elements (which are used in camera lenses now) haven't seen any applications in EPs, where some of the same problems need to be solved?

    @bassplayer:
    Quote:

    What about a secondary mirror suspended by powerful magnets.






    Best,
    Mark


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    RobDob
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    Re: Trends, future trends, and "should be dones"... new [Re: mark cowan]
          #5335847 - 07/26/12 12:34 AM

    Great thread Mark!

    It's sparking the peanut inside my head.

    Here's an idea about conventional mirrors: I'm wondering if there is any way to hog out or mill away the glass in the back end of a conventional mirror, say in a honeycomb pattern to retain rigidity yet shed alot of weight, without affecting the figure?

    Perhaps, may be able to have a mirror at half the weight with better thermal qualities?

    Or, do this to the blanks before figuring?

    The mechanics of this do seem a little scary and expensive...

    Rob


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    Dick Jacobson
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    Re: Trends, future trends, and "should be dones"... new [Re: mark cowan]
          #5336714 - 07/26/12 02:01 PM Attachment (24 downloads)

    One word (and it's not "plastics"): Rings.

    I'm talking about two types of rings: metal structural rings for building tubes and mounts, and Lazy Susan rings for tube rotation and other things.

    If you can bend a metal tube, bar, or other shape into a circle, it makes a great structural element for building tubes, secondary cages, and altitude bearings. An aluminum ring has a much greater strength-to-weight ratio than a plywood ring. It's easy to bend metal into circles using this tubing roller.

    To make a rotating tube, I have used a single Lazy Susan ring which is a permanent part of the tube. I've also used these to make rotating secondary cages and as part of a polar axis. The ones I've used can be found at Lee Valley Hardware and other vendors. Other people have used the bearings sold by VXB which appear to be thinner but come in a wider range of sizes. They can also be used as structural elements if you don't want to go to the trouble of bending your own metal.

    The picture below shows a very strong yet lightweight mirror support structure that I made by bending a 3/16" x 3" aluminum bar using the Harbor Freight tool. I bolted the ends together using a small scrap of material bent to the same radius.


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    Re: Trends, future trends, and "should be dones"... new [Re: RobDob]
          #5336825 - 07/26/12 02:57 PM

    Quote:

    Here's an idea about conventional mirrors: I'm wondering if there is any way to hog out or mill away the glass in the back end of a conventional mirror, say in a honeycomb pattern to retain rigidity yet shed alot of weight, without affecting the figure?




    Yes. Pocket milling. Followed by sand blasting to smooth the rough contours and reduce the strain induced. Greg Rhode and I were considering this for a while with quartz blanks to get the weight down.

    But it has to be done before the mirror is figured as it will affect the figure. Except in the case of single-crystal (silicon carbide) substrates, this is a technique used by NASA and others to make ultra-light mirrors for space. Since the material is all one crystal it has zero strain and milling doesn't affect it. Downside is it costs a lot.

    Best,
    Mark


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    Re: Trends, future trends, and "should be dones"... new [Re: Dick Jacobson]
          #5336831 - 07/26/12 02:58 PM

    Rings - I'm liking that a lot.

    Best,
    Mark


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    tim53
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    Re: Trends, future trends, and "should be dones"... new [Re: mark cowan]
          #5339075 - 07/27/12 08:50 PM

    I used lazy suzan bearings for rotating rings on my 10" f/6 "Delmarvascope". They're going to need some stiffening, as they do flex a little. Hasn't been a problem so far, since I use the scope mostly for planetary imaging.



    For my 8" f/9 scope, I picked up some smaller rings and made the tube so they'd just fit over it. I'll still make reinforcement rings out of plywood, but this time I think I'll also make a 'brake' system and leave the ball bearings inside - on the 10", I took them out and made delrin rods to bear on the inside groove.

    Here are the two rings I plan to use, laying up against the forms I used to clamp the tube and keep it round while the glue dried. The smaller bearing I'm thinking of using to make a rotating focuser.



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    Pinbout
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    Re: Trends, future trends, and "should be dones"... new [Re: tim53]
          #5339088 - 07/27/12 09:00 PM

    Hey tim,

    do you have a brake on the rings so you can stop them from rotating?


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    tim53
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    Re: Trends, future trends, and "should be dones"... new [Re: Pinbout]
          #5339221 - 07/27/12 10:45 PM Attachment (12 downloads)

    Hi Danny:

    Not on the 10". But with that one, I took the ball bearings out, drilled the outer rings for threaded delrin rods, and I tighten them to add tension. It works okay, but the advantage of the bearings was that they supported the rings all the way around, and I think I only have 3 or 4 delrin rods per ring, so they are only supported every 90 degrees or so.

    So this time, I'm going to rig up a brake of some kind. Here's a shot of one of the rings around the tube for my 8" f/9, to show how close they fit.

    -Tim.


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    Dick Jacobson
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    Re: Trends, future trends, and "should be dones"... new [Re: tim53]
          #5339226 - 07/27/12 10:47 PM

    Very nice work on your 10", tim53! Just curious, you said you substituted delrin rods for the ball bearings, how did you get the rings back together with the rods inside? I've experimented a lot with different lubricants but have always put the ball bearings back inside. The ball bearings have uneven friction when the rings are tipped sideways. Is the delrin better?

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    Re: Trends, future trends, and "should be dones"... new [Re: Dick Jacobson]
          #5339255 - 07/27/12 11:11 PM

    Quote:

    For my 8" f/9 scope, I picked up some smaller rings and made the tube so they'd just fit over it. I'll still make reinforcement rings out of plywood,




    Are these rings made to take side loads as well as vertical? Were they not stiff enough just because of the material used?

    Best,
    Mark


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    tim53
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    Re: Trends, future trends, and "should be dones"... new [Re: mark cowan]
          #5339372 - 07/28/12 01:25 AM

    Dick:

    I drilled holes through the outer ring in 4 places 90 degrees apart and put these in. Here I'm turning a beveled tip on one of the delrin rods to match the bearing groove on the inside ring.



    then I threaded the rod while it was still in the late:



    And here's one in the ring where I drilled and tapped it.



    I probably should have used teflon rods, as they'd be slipperier. The bearings did tend to love in fits and starts, though, so I thought this would be better. At least the tension is adjustable.

    I think the smaller rings will be stiffer, since the aluminum is about the same width and thickness. So some sort of brake to tension against one of the rings would hopefully be sufficient to keep it from moving when I don't want it to.

    -Tim.


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    Dick Jacobson
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    Re: Trends, future trends, and "should be dones"... new [Re: mark cowan]
          #5342408 - 07/29/12 09:23 PM

    Quote:

    Are these rings made to take side loads as well as vertical? Were they not stiff enough just because of the material used?

    Best,
    Mark



    It's hard to tell from the photo, but I suspect that the lack of stiffness might be due to the base plate not being stiff enough. I used just a single ring between fork arms. The ring flexed too much until I reinforced it with a square aluminum frame.

    These rings do seem capable of supporting a large lateral load.


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    tim53
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    Re: Trends, future trends, and "should be dones"... new [Re: Dick Jacobson]
          #5343093 - 07/30/12 10:15 AM

    Yep.

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    Dick Jacobson
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    Re: Trends, future trends, and "should be dones"... new [Re: tim53]
          #5345016 - 07/31/12 10:46 AM

    Quote:

    So some sort of brake to tension against one of the rings would hopefully be sufficient to keep it from moving when I don't want it to.

    -Tim.



    I made a brake using a polyethylene pad glued to a piece of aluminum, which provides enough friction to prevent unwanted movement.


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    Pinbout
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    Re: Trends, future trends, and "should be dones"... new [Re: tim53]
          #5382478 - 08/23/12 10:37 AM

    Quote:

    If the glass is truly liquid when in the rotating furnace, it should be possible to produce a perfect parabola, similar to how mercury mirrors are "made" and used.




    ok tim, I found it. Roger Angel at univ of arizona.

    scroll down the page, rotating furnace...

    Roger Angel


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    Re: Trends, future trends, and "should be dones"... new [Re: Pinbout]
          #5382910 - 08/23/12 02:27 PM

    Yes it takes that rough shape (if that's what you mean), but it still requires grinding, polishing, and figuring to complete the mirror.

    Best,
    Mark


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    kfrederick
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    Re: Trends, future trends, and "should be dones"... new [Re: mark cowan]
          #5383581 - 08/23/12 09:42 PM

    http://www.gmto.org/ Six 8.4 meter F.7 off axis mirrors And one on axis mirror

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    Crayfordjon
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    Re: Trends, future trends, and "should be dones"... new [Re: kfrederick]
          #5383940 - 08/24/12 03:54 AM

    I know these comments will fall on stony ground, but you ask for new trends in instrument design to help newcomers and others with small budgets, I have floated a concept where a cheap but very effective beginners refractor can be made for a song,, the draw back is that there is a marginal amount of colour left in the image which does not in any way spoil the seeing. This concept is too radical for most on CNR and has generally been treated with hostility, incomprehension and contempt by a community imbued with the concept that a telescope must be "perfect", otherwise it is "useless". It may be a matter of curiosity to note that the concept I have launched has been enthusiastically taken up by people in Brazil and France, and these scopes are being made and used. Hmmmm, says something dont it!. Radically new concepts in the way we use and design scopes is beyond most here.

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    kfrederick
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    Re: Trends, future trends, and "should be dones"... new [Re: Crayfordjon]
          #5384055 - 08/24/12 07:32 AM

    I hear you John I do not know why there is so much incomprehension of your efforts .I think your telescopes are great . The same with the CHief every one ED made has worked but there is still talk that they cannot work and no interest . It is great that we can talk ideas . I think all types of telescopes are cool none better all cool . Telescopes have no brain for me it is the ATM friends that is the goal . If a new ATM learns how to grind and test a mirror then he is ready to try all the new one of the kind designs .And if problems come up that ok . I respect your work .

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    John Jarosz
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    Re: Trends, future trends, and "should be dones"... new [Re: kfrederick]
          #5384143 - 08/24/12 09:16 AM

    It is true that many souls on CN and astronomy forums in general seem to obsessed by the concept of optical perfection and/or factory perfection to the exclusion of any other topic. We don't have many of those guys here in the ATM forum because most builders know there is no perfection in hardware, perfection is only in the sky.

    It's really too bad such an affliction prevents the trial of new ideas and concepts. Thanks to Ed and Mike Jones, Ed Turcow ( I love the F1 scope), Mark Harry and others (you too John) who are thinking out of the optical box so we can further understand the ATM world where Horace Dall's spirit lives on. We need more screwy ideas, even if they're not perfect.

    John


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    mark cowan
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    Re: Trends, future trends, and "should be dones"... new [Re: Crayfordjon]
          #5384742 - 08/24/12 03:06 PM

    Quote:

    I know these comments will fall on stony ground, but you ask for new trends in instrument design to help newcomers and others with small budgets




    There's no stony ground in my crop circle, but if you could post a link that would help, as I missed this one.

    I've noticed both the intense dislike of innovation expressed by some here on CN (it's inexplicable to me) that sometimes expresses itself as outright derision of new directions. I also notice a slowness to embrace innovative ideas that's troubling as well, but I always give advice not to be swayed by that. Good ideas will win out eventually.

    So a couple examples - I came up with a new wire spider design, through testing and experimentation, that is fully stable against vibration without the use of high tension on the strings, thus allowing thinner wires to improve diffraction. So far two people I know of have built one from my design. Now, of the rather small number of people that build wire spiders in the first place (and I've been promoting them for over 15 years) that's actually pretty good. But this design won't catch on very fast until I actually manufacture them in telescopes (this is on the horizon now).

    For most (even some ATMs) if you can't BUY it it doesn't exist. If it isn't IN the market already it can't even be considered. If nobody MAKES an ultrafast, ultralight, ultraportable high performance 'scope it doesn't exist. That opens an opportunity for anybody who can find a better way to do things and bring them to market, but it seems an inescapable aspect as well to how the majority of people think. They just DON'T innovate, they don't look at a problem or an existing approach and ask themselves how to make it better or simpler or cheaper or easier. They play with the toys they have, not the toys they could have.

    The second example comes from almost as close to home, Jerry Oltion in Eugene invented and perfected a simple drive for ballscopes that he calls the "Trackball" and put it in the public domain (same as my spider design is available to anybody free). I'd seen it before, liked it, but didn't do anything further - until this year at the Oregon Star Party, where Jerry was showing it off and suddenly it clicked in my head - I'd been wanting to build a new structure for my 8" f/5.8 and I REALLY wanted tracking for that planetary instrument. Jerry commented how he'd put maybe $30 into building the entire drive for his 10" f/4.

    That fire caught, I got some details and made reference pics of his 'scope (here we are on Mars ),

    I've ordered the 13" playground ball I need to use for the fiberglass ball construction (it'll be here today !) and I'm off to the races. Better ideas do propagate.

    But why I'm telling this story - Jerry said he DOESN'T UNDERSTAND WHY MORE PEOPLE DON'T BUILD HIS DESIGN. He's been showing it and talking it up, he's got it fully documented online. It took a couple years for me to go OH YEAH I NEED THAT and now I'm going to basically follow his plans as closely as possible. But I invent things so I'll try to improve where possible - he said he'd like to see a cleaner implementation of the drive assembly itself and I already see how to fabricate that out of a few pieces of aluminum.

    As a maker of optics and occasional telescope designer I'm working on extremely thin meniscus mirrors currently. On my polisher is a 14.7 f/3 quartz experiment that's 0.27" thick - 54:1 aspect ratio. Support is crucial for such things. I've got a simple mirror-cell design that I'm going to be patenting for use with this and much larger versions. Reasons for doing this should be obvious, but of course a patented design can always be built by individuals for their own use freely.

    For the above project however there are no guarantees of success. If it fails it won't be the first time my ideas have bit the dust. But I've already seen signs that it's going to work, in the sense of perfectly regular astigmatism on the first attempt (you gotta be an optician to love that).

    I guess what I'm trying to say is that it's often frustrating for the people who do think outside the box. Inventions often seem obvious in retrospect. But if they were obvious - why did nobody else ever come up with them?

    Best,
    Mark


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    careysub
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    Re: Trends, future trends, and "should be dones"... new [Re: mark cowan]
          #5386221 - 08/25/12 12:09 PM

    Quote:

    ...
    That fire caught, I got some details and made reference pics of his 'scope (here we are on Mars ),
    ...
    I've ordered the 13" playground ball I need to use for the fiberglass ball construction (it'll be here today !) and I'm off to the races. Better ideas do propagate....




    Thanks for the link, very interesting.

    Far be it from me to suggest that anybody on this forum shouldn't make some telescope part himself if he has a mind to do so, but Jerry's page does mention that he ended up going with commercially made acrylic spheres after trying making a fiberglass one himself.

    There are a lot of plastic sphere manufacturers it appears with a little Googling, though in the larger sizes they generally require requesting a quote (usually a bad sign for a one-off I think). Interestingly, this manufacturer page:

    http://cicball.thomasnet.com/viewitems/hollow-plastic-balls/large-hollow-plastic-balls?

    actually lists "telescope bodies" as one of the typical uses for their products.


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    mark cowan
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    Re: Trends, future trends, and "should be dones"... new [Re: careysub]
          #5386462 - 08/25/12 02:44 PM

    I don't think that's what it says at all - the ones he's been using in the field are fiberglass, and the acrylic spheres require reinforcement at the lip. I was there.

    Quote:

    My fiberglass spheres were strong enough to not need any stiffening material around the opening, but a factory-made sphere (or a hemisphere) might be thinner and/or more flexible. If it is, you'll want to attach a ring around the top to reinforce it.




    The thing you can't get from the pictures (nor really my poor pic below) is the indestructible quality of the sphere itself, with epoxy paint on it to give a little texture in appearance and feel it's very high end. That was what got me really interested, the way the whole thing worked together, and that if I just followed the plan I'd end up with something perfect.



    Cheap and relatively easy has great appeal as well, the ball is just the mold and reusable without damage (deflate and remove, leaves a lovely light-absorbing etched pattern on the inside). You do need a particular size for any given mirror. This is the right size for my 8" mirror conversion.



    However, the requirements for the ball itself to make it track properly (and slew by hand easily) are specific - obviously it needs to be very round (you do this in sanding it down), it needs to have some texture for grip on the drive mechanism, it needs to slip on command - Jerry gets this using some ski wax on the epoxy paint. And it needs to be strong and not brittle. Various plastics could do this, for commercial production that'd be a topic for research.

    NB: I see where that link says "telescope bodies" but figure some of that's customer inquires. I haven't seen many of these made. I think the "large animal toy" category is a lot more evocative, personally.

    For more pics scroll down Mel Bartel's OSP Walkabout, just posted. And oh yeah - NO DOBSON'S HOLE!

    Best,
    Mark


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    Pinbout
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    Re: Trends, future trends, and "should be dones"... new [Re: mark cowan]
          #5386699 - 08/25/12 05:18 PM Attachment (11 downloads)

    hey I was playing with truss ends similar to those...

    truss connection

    got tired of giving moonlite all my money...


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    mark cowan
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    Re: Trends, future trends, and "should be dones"... new [Re: Pinbout]
          #5388210 - 08/26/12 04:05 PM

    Those are nice. What did you use for the padding?

    The scope looks quite stable but I get the feeling there's something missing somewhere.

    Best,
    Mark


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    Pinbout
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    Re: Trends, future trends, and "should be dones"... new [Re: mark cowan]
          #5388610 - 08/26/12 07:55 PM

    Padding? Are you asking about the 13/16 phenolic balls, the same balls moonlite uses?

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    mark cowan
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    Re: Trends, future trends, and "should be dones"... new [Re: Pinbout]
          #5388781 - 08/26/12 09:31 PM

    I guess, it's hard to tell what they are just looking...

    Best,
    Mark


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    spudrick
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    Re: Trends, future trends, and "should be dones"... new [Re: Pinbout]
          #5388841 - 08/26/12 10:10 PM

    Hello Danny
    I watched the Video you made to show the connectors, looks good! I should be able to make these connectors for my future 17.5 build, what size is the tubing you have used? I think i should be using 1" or 1 1/4" tubing for my build, do you have a link to the supplier of the balls? I searched here in Australia and they are available but looks to be limited for shaft size. And did you use same connectors for top and bottom
    Thanks Terry


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    Pinbout
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    Re: Trends, future trends, and "should be dones"... new [Re: spudrick]
          #5388868 - 08/26/12 10:24 PM

    mcmaster carr under their plastic thread ball knobs

    the balls have a 1/4-20 brass press fit insert. so I put a set screw in the tube connecting nut and screwed the balls to the end of the tubing.

    I'm making a small scope so I used 5/8 tubing.

    moonlites uses the 13/16 balls on both the 1" tubing or the 1-1/4 tubing connectors.

    you could put a washer and a nut between the tubing and ball since the larger tubing could get in the way when moving the tube around.


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    spudrick
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    Re: Trends, future trends, and "should be dones"... new [Re: Pinbout]
          #5388900 - 08/26/12 10:44 PM

    Thanks Danny, i see them on McMasters site and found the same are available here (4 times the price!) various sizes available.
    So now i will work toward using these on the scope, they seem to be pretty easy to make.
    Terry


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    Pinbout
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    Re: Trends, future trends, and "should be dones"... new [Re: spudrick]
          #5388919 - 08/26/12 10:50 PM

    appearences can be deceiving...

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    mark cowan
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    Re: Trends, future trends, and "should be dones"... new [Re: Pinbout]
          #5389837 - 08/27/12 02:07 PM

    Could you post a picture of those ballends (know that I know what they are ) taken apart so I can see how they're made?

    Best,
    Mark


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    Pinbout
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    Re: Trends, future trends, and "should be dones"... new [Re: mark cowan]
          #5390005 - 08/27/12 03:53 PM Attachment (24 downloads)

    I know your being kind, asking questions as if someone cares...

    how 'bout a drawing...


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    cheapersleeper
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    Re: Trends, future trends, and "should be dones"... new [Re: Pinbout]
          #5390047 - 08/27/12 04:19 PM

    I care!! I care very much. If I build any more scopes, pragmatic decisions are going to force me toward truss dobs, which I mistrust on principle. If I am going to build something that I do not trust, I need all the help I can get.

    Regards,
    Brad


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    spudrick
    member


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    Re: Trends, future trends, and "should be dones"... new [Re: Pinbout]
          #5390105 - 08/27/12 04:58 PM

    I care as well, i will be using these for my build. This is just another example of help and sharing on this community
    Thank you
    Terry


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    mark cowan
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    Re: Trends, future trends, and "should be dones"... new [Re: Pinbout]
          #5390311 - 08/27/12 07:39 PM

    Quote:

    I know your being kind, asking questions as if someone cares...




    No I'm not, I'm rarely kind, just curious. Stuff I've built so far uses tubes or poles and strings, not struts (except one full-scale model). But the trackball conversion will use some sort of (likely carbon fiber) struts and I've already seen a couple ways of anchoring them. With the balls you don't have to drill the holes on complicated angles, no?

    Anyway, see I would have just drilled blind holes in the balls to the size of the tubes and then epoxied them into place or something like that. KSSS rules.

    Best,
    Mark


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    Pinbout
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    Re: Trends, future trends, and "should be dones"... new [Re: mark cowan]
          #5390335 - 08/27/12 07:52 PM

    Quote:

    With the balls you don't have to drill the holes on complicated angles, no?






    correcto-mundo.


    Quote:

    would have just drilled blind holes in the balls to the size of the tubes and then epoxied them into place





    that means the balls would be a lot bigger than the tube. with these the balls are small and inexpensive.


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    mark cowan
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    Re: Trends, future trends, and "should be dones"... new [Re: Pinbout]
          #5390464 - 08/27/12 09:35 PM

    OK, I looked at the Moonlite page and I see what you mean. In general anyway.

    Best,
    Mark


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    careysub
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    Re: Trends, future trends, and "should be dones"... new [Re: Pinbout]
          #5390523 - 08/27/12 10:20 PM

    Albert Highe has a somewhat different scheme in the same spirit in his new book (see pp. 506 and 572). He holds the two balls by sandwiching them between chamfered holes in the plywood LTA top and a clamp plate drilled through held down with a single bolt.

    He uses a 1/4" aluminum top plate, as an alternative I imagine a chamfered wood plate (for the mating surface) backed by a steel plate for stiffness would work as well (solid wood would likely be too thick).


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    Roy McCoy
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    Re: Trends, future trends, and "should be dones"... new [Re: Pinbout]
          #5390557 - 08/27/12 10:43 PM

    Nice sketch Danny.

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    Roy McCoy
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    Re: Trends, future trends, and "should be dones"... new [Re: tim53]
          #5390568 - 08/27/12 10:50 PM

    Thanks for those pictures Tim!

    I bought one of the lazy susan bearings and felt it was too loose for my purposes, until now.

    Regards,

    Roy


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    Pinbout
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    Re: Trends, future trends, and "should be dones"... new [Re: careysub]
          #5390570 - 08/27/12 10:52 PM

    Quote:

    He holds the two balls by sandwiching them between chamfered holes in the plywood




    this is for a small telescope with not much weight. if I was going to do it for a lot of torque I would drill thru the bottom and let the angled twist drill bit create that inside chamfer so it would keep the balls from popping out.


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    KidOrion
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    Re: Trends, future trends, and "should be dones"... new [Re: Pinbout]
          #5391628 - 08/28/12 02:24 PM

    Quote:

    Quote:

    With the balls you don't have to drill the holes on complicated angles, no?






    correcto-mundo.


    Quote:

    would have just drilled blind holes in the balls to the size of the tubes and then epoxied them into place





    that means the balls would be a lot bigger than the tube. with these the balls are small and inexpensive.




    These are a great idea. Is there any slippage in use? I'd like to use these for a 13.1" Dob, although my UTA will probably be fairly weighty. Do you have any issues with keeping the UTA centered/truss-pole slippage?


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    Pinbout
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    Re: Trends, future trends, and "should be dones"... new [Re: KidOrion]
          #5391961 - 08/28/12 05:37 PM

    No. But if your concerned about that drill with a 7/8 twist drill to chamfer the top inside surface to leave an openning of only 3/4 clearance.

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    mark cowan
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    Re: Trends, future trends, and "should be dones"... new [Re: Pinbout]
          #5393542 - 08/29/12 04:11 PM

    FWIW here's something I did a while a back on what I call the "full scale model" - it was for a 12.5" f/6 folded dob of a new design that never got finished as I revised the build parameters repeatedly. These are just wooden balls epoxied into the ends of the tubes, they join to PVC holders that were boiled and fit while soft. Unfortunately for this prototype the holders never really lock on as built, and the whole thing will fall apart if any of the tubes are knocked loose. But for a truss where there are 3 different lengths and (I think) 6 different angles (some are mirror images) using ball ends solves a lot of the difficulty of attachment (the secondary ring is on about a 30 degree angle, BTW). With some strings it would be quite stable, but it was never designed to be a string scope (I don't think they existed yet. )



    Best,
    Mark


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    cheapersleeper
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    Re: Trends, future trends, and "should be dones"... new [Re: mark cowan]
          #5393557 - 08/29/12 04:18 PM

    I was thinking about the earlier digression regarding ATMs being slow to adopt or resistant to new designs. Obviously, I can speak only for myself, but for me, to even begin to understand a new design I have to see several examples of it and see several explanations of how/why/what the hell before I could even begin to think about building one. I am sure that some here are a lot more competent as scope builders than I am, but I am also sure that a lot of ATM are just bright people that work in fields that do not particularly prepare them to be building telescopes.

    If you want new designs adopted, loads of pics and documentation of several builds would go a long way.

    Regards,
    Brad


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    mark cowan
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    Re: Trends, future trends, and "should be dones"... new [Re: cheapersleeper]
          #5393913 - 08/29/12 08:35 PM

    I can relate to that. But when I first saw Mel Bartel's "ZipDob" in the flesh, it was awfully hard to wrap my head around it. Now it's easier, and it's settled into a particular design category that helps it make sense.

    I suspect that anything that includes a radical re-imagining of what's been done before suffers somewhat the same fate. You just can't "see" it for awhile.

    Best,
    Mark


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    radicell2
    member


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    Re: Trends, future trends, and "should be dones".. new [Re: mark cowan]
          #5400892 - 09/03/12 11:15 AM



  • Ultra-thin mirrors leading to superb thermal performance (though this needs to apply to secondaries as well at some point).





    One with no conventional floatation cell is called a Double Arch layout.You can see an example plus research PDF files at:
    http://www.rokoszoptical.yolasite.com
    (not selling anything from this site)
    Ric

    Edited by radicell2 (09/03/12 11:24 AM)


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  • mark cowan
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    Re: Trends, future trends, and "should be dones".. new [Re: radicell2]
          #5401501 - 09/03/12 05:21 PM

    Hi Ric,

    I recall browsing your designs not that long ago.

    The approach I'm taking is different and simpler but it does depend on cell design to work well. Can't say yet whether it's going to fly.

    Best,
    Mark


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    radicell2
    member


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    Re: Trends, future trends, and "should be dones".. new [Re: mark cowan]
          #5402588 - 09/04/12 09:40 AM

    Quote:

    Hi Ric,

    I recall browsing your designs not that long ago.

    The approach I'm taking is different and simpler but it does depend on cell design to work well. Can't say yet whether it's going to fly.

    Best,
    Mark




    Have added a new PDF file in the Double Arch section,plus a very expanded "Lessons Learned" tutorial.

    Ric


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    Pinbout
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    Re: Trends, future trends, and "should be dones".. new [Re: radicell2]
          #5402659 - 09/04/12 10:17 AM

    this is a should be done...

    not my idea but

    right angled polar scope

    at 2:33 you can hear the "old guy" tell ioptron's CEO.


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    TxStars
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    Re: Trends, future trends, and "should be dones".. new [Re: Pinbout]
          #5402677 - 09/04/12 10:23 AM

    The next thing for large Dob's will be the "trailer transformer".
    You pull up hit the switch and the trailer opens up.
    Then the scope folds out ready to use.


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    mark cowan
    Vendor (Veritas Optics)
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    Reged: 06/03/05

    Loc: salem, OR
    Re: Trends, future trends, and "should be dones".. new [Re: radicell2]
          #5403148 - 09/04/12 02:43 PM

    Quote:

    Have added a new PDF file in the Double Arch section,plus a very expanded "Lessons Learned" tutorial.




    Thanks, I'll have a look!

    Best,
    Mark


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    Pinbout
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    Re: Trends, future trends, and "should be dones".. new [Re: mark cowan]
          #5404517 - 09/05/12 09:12 AM Attachment (12 downloads)

    how about instead of trying to retrofit lazy-suzy's rings for rotating rings make a like a crayford bearing surface, ie kineoptic's focuser...

    [i should check spelling before I save the pic ]


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    Dick Jacobson
    scholastic sledgehammer


    Reged: 12/22/06

    Loc: Plymouth, Minnesota, USA
    Re: Trends, future trends, and "should be dones".. new [Re: Pinbout]
          #5404793 - 09/05/12 12:24 PM

    Quote:

    how about instead of trying to retrofit lazy-suzy's rings for rotating rings make a like a crayford bearing surface, ie kineoptic's focuser...



    Nice idea, but the tube surface would have to be very stiff, and the tube might tend to creep longitudinally as it was turned back and forth. A Lazy Susan provides smooth rotation with no creep.


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    Pinbout
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    Re: Trends, future trends, and "should be dones".. new [Re: Dick Jacobson]
          #5404891 - 09/05/12 01:24 PM

    Quote:

    and the tube might tend to creep longitudinally as it was turned back and forth.




    besides just being a conceptual sketch that design has a tensioner, and the tube can be push/pulled to help balance the scope

    when on a eq I never rotated the tube that much so the travel could be very minimum.

    the loosy suzzies have to be modded, there is no brake, or clamping mechanism.

    I really appreciate tim53's work earlier in the thr'd.

    I just want to think of other ways to skin a cat. in this case a round alum tube cat, or really newt, save the cats for the other forum.


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    mark cowan
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    *****

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    Loc: salem, OR
    Re: Trends, future trends, and "should be dones".. new [Re: Pinbout]
          #5405032 - 09/05/12 02:48 PM

    Quote:

    how about instead of trying to retrofit lazy-suzy's rings for rotating rings make a like a crayford bearing surface, ie kineoptic's focuser...




    I suspect this would work quite well if you had used hard rubber or neoprene contact surfaces. But why offset the angles if it's just for rotation?

    Best,
    Mark


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    Pinbout
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    Re: Trends, future trends, and "should be dones".. new [Re: mark cowan]
          #5405117 - 09/05/12 03:34 PM

    Quote:

    But why offset the angles if it's just for rotation?






    to push or pull the tube for balance changes...


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    Pinbout
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    Re: Trends, future trends, and "should be dones".. new [Re: TxStars]
          #5405131 - 09/05/12 03:43 PM Attachment (7 downloads)

    Quote:

    The next thing for large Dob's will be the "trailer transformer".
    You pull up hit the switch and the trailer opens up.
    Then the scope folds out ready to use.




    I don't know about automation but bizbox makes trailers pretty easily transform

    I dont see why you couldn't roll the roof off and voila...


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    mark cowan
    Vendor (Veritas Optics)
    *****

    Reged: 06/03/05

    Loc: salem, OR
    Re: Trends, future trends, and "should be dones".. new [Re: Pinbout]
          #5405424 - 09/05/12 06:49 PM

    Quote:

    to push or pull the tube for balance change




    Oh, I see how that would work...

    Best,
    Mark


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    tim53
    Postmaster
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    Reged: 12/17/04

    Loc: Highland Park, CA
    Re: Trends, future trends, and "should be dones".. new [Re: Pinbout]
          #5406614 - 09/06/12 01:55 PM

    Quote:

    this is a should be done...

    not my idea but

    right angled polar scope

    at 2:33 you can hear the "old guy" tell ioptron's CEO.




    ESPECIALLY when polar aligning a big EQ mounted Newt with a short pier!

    I use mine for planetary imaging, and now I've got enough firewire and USB web and machine vision cameras that I think I'll take one and adapt it for afocal imaging through the polar scope. That way, I can comfortably watch the reticle on my laptop while I tweak the screws on the mount. All without craning my neck (which hates being craned these days!).

    -Tim


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    tim53
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    Loc: Highland Park, CA
    Re: Trends, future trends, and "should be dones".. new [Re: Pinbout]
          #5406628 - 09/06/12 02:05 PM

    Quote:

    how about instead of trying to retrofit lazy-suzy's rings for rotating rings make a like a crayford bearing surface, ie kineoptic's focuser...

    [i should check spelling before I save the pic ]




    Love the drawing!

    I think some manufacturer did something like this back then in the 50s or 60s, but I'm not remembering who that was. I do recall that the Treckerscope Galaxy that Don Surles sold a couple years back had something along those lines, but the wheels bore against another ring and not the tube.

    My Optical Craftsmen 8" Connoisseur has very simple rotating rings, that are probably most comparable to the "Wilcox rings" you see people making these days. They're surprisingly effective, too. And would probably be a lot cheaper to make than Cave or Parks rings.

    They're simply two sets of clamping rings - one set attached to the saddle, with the spacer rods and the guide scope bracket attached, and the other set attached to the tube. the set on the tube are machined on one face to slide against nylon bolt heads on the rings fixed to the saddle. Here's one pair separated to show the machined surface and the nylon bolts



    I've been thinking about making my next lazy susan rotating rings without so much modification as I did on the ones for my 10". Instead of going to all that trouble, I might swap the steel ball bearings out for nylon ones from MacMaster Carr or something. Should be smoother. Would still need to rig up a brake, though.

    -Tim.


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