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Trends, future trends, and "should be dones"...

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#1 mark cowan

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Posted 16 July 2012 - 01:06 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! :jump:[/quote]
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

#2 cheapersleeper

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Posted 16 July 2012 - 01:25 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.

#3 jwaldo

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Posted 16 July 2012 - 01:32 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.

#4 Benach

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Posted 16 July 2012 - 01:33 PM

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

These exist already for 100+ years.

#5 RossSackett

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Posted 16 July 2012 - 01:39 PM

Right on, Mark.

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

#6 Dick Jacobson

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Posted 16 July 2012 - 03:26 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.

#7 MitchAlsup

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Posted 16 July 2012 - 04:29 PM

[*]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.

#8 kfrederick

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Posted 16 July 2012 - 04:45 PM

Bigger and faster with thin mirrors .

#9 NHRob

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Posted 16 July 2012 - 08:15 PM

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

#10 RossSackett

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Posted 16 July 2012 - 09:19 PM

CNC templets for milling wooden scope parts

#11 mark cowan

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Posted 19 July 2012 - 09:38 PM


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. :grin: Though that's not a dob thing. :lol:

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.

Bigger and faster with thin mirrors .


I hope that goes without saying... :cool:

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

#12 EyeSage

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Posted 19 July 2012 - 11:42 PM

  • 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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#13 Dick Jacobson

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Posted 20 July 2012 - 03:54 AM

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.

#14 Pinbout

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Posted 20 July 2012 - 11:46 PM

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. :tonofbricks:

#15 PierreDesvaux

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Posted 21 July 2012 - 03:05 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...

#16 kfrederick

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Posted 21 July 2012 - 05:45 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 .

#17 haywool

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Posted 21 July 2012 - 06:28 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 ??

#18 Jon Isaacs

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Posted 21 July 2012 - 06:34 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

#19 Pinbout

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Posted 21 July 2012 - 07:54 AM

- 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 :grin:

#20 Jeff Morgan

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Posted 21 July 2012 - 10:11 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.

#21 tim53

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Posted 21 July 2012 - 10:35 AM

Suspend a monolayer of aluminum in a tuned magnetic field?

-Tim.

#22 tim53

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Posted 21 July 2012 - 10:36 AM

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

-Tim.

#23 careysub

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Posted 21 July 2012 - 11:33 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.


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?

#24 Jon Isaacs

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Posted 21 July 2012 - 12:16 PM

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

#25 careysub

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Posted 21 July 2012 - 02:43 PM

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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