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Foldable Reflecting Telescope

3d printing Catadioptric DIY Equipment Mirror Making Optics
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#1 alexcraven

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Posted 10 October 2024 - 08:30 AM

Hi all,

 

I'm looking into making a foldable reflecting telescope, with a mechanism similar to that on JWST. The goal is for the eyepiece to be mounted close to the primary mirror, with the secondary mirror folding out to wherever it needs to be. My knowledge of telescope making is very limited, as I have only made a Newtonian Telescope. That telescope has a 114 mm diameter primary mirror, which is about the size I would want to use to make this new one. This project has presented several challenges that I am unsure of how to approach, mainly:

 

1. What type of telescope design should I use?

(Right now, I plan on making something similar to this: https://www.youtube....ximumAstronomy)

2. Where do I source the mirrors for this?

3. How do I calculate the distances between each mirror and the optics?

4. How do I make this cheap?

 

If anyone could offer some insight that would be really appreciated. 



#2 TOMDEY

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Posted 10 October 2024 - 09:50 AM

That 70" folded Newt results in a gargantuan central obstruction and poor imagery because of SM support issues. In your modest size, consider an off-axis paraboloidal primary, so the folding flat doesn't shadow the PM at all. Keeping direct sky light from reaching the image is also a challenge. I presume you want to do this just for the fun of it? For the slow 70" the motivation was to get the image closer to the ground. For a 5-inch scope that's Meh, unless the PM is very slow (long focal length) possibly even counterproductive. But just for fun, it would be interesting to build.

 

I have these magnificent ULE off-axis paraboloidal PM's, intending to build a binoscope with them... some day.        Tom

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  • 137 Tom's Off Axis Parab Binoscope Objective Mirrors.jpg


#3 Daveatvt01

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Posted 10 October 2024 - 10:38 AM

Hi and welcome!

Perhaps tell us why you would like this particular setup? That will help guide recommendations.



#4 alexcraven

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Posted 10 October 2024 - 11:26 AM

I am mainly making this for fun, I already have 2 telescopes, and this wouldn't beat them in terms of performance. Also, I want to make a telescope that can be portable, handheld, and take up as little space as possible when not in use. I intend on 3d printing most of it, and sourcing mirrors and the focuser online. I attached a picture of my first telescope, BLT (Bizarre Little Telescope), and a simple sketch of what I intend on making. I found the secondary and primary mirror for BLT from a website which I am unable to find anymore, and it was around 70-80 dollars for both if I remember correctly. I am not super picky about image quality, I am mostly looking for something cheap and something that works. My biggest problem is finding cheap Cassegrain mirrors that would work with this telescope.

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#5 triplemon

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Posted 11 October 2024 - 12:35 AM

I want to make a telescope that can be portable, handheld, and take up as little space as possible when not in use.

I think folding/rotating the components at that tiny size (4.5 inch) is unlikely to result in notable space savings compred to just making a collapsible setup that reduces the length of the setup.

 

And handheld - well - how much magnification do you want to get ? Using binoculars the end of handholdability is around 15-20x magnification. And even heavier, less sturdy and compact devices would likely be limited to less. So I would still seriously think of how to put this telescope on terra firma. In particular if you want to build an cassegrain.

 

On the source of parts - look at craigslist or goodwill. Older 5 inch department store newtonians come up frequently for 20 dollars there. The mirrors will be fine, the focusers maybe and the mounts never usefull - so that is all you want. For a cassegrain there would be damaged C5's at best.


Edited by triplemon, 11 October 2024 - 12:38 AM.

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#6 Sincos

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Posted 12 October 2024 - 11:18 AM

Can remember at least two commercial variations being sold that meet most of your criteria. The old Coulter Company offered a foldable handheld reflector ( the C-50 ? ) sometimes one shows up in the classifieds. Then also the AstroScan was compact handheld , came with a carry strap . With those in mind you just need to come up with a way to move the mirror into operating position  .  Like a violin where the eyepiece is the chin part and the mirror the fingerboard, there done thank you very much  ;  )

 

oh yeah welcome.gif and never stop coming up with ideas to try


Edited by Sincos, 12 October 2024 - 11:22 AM.


#7 speedster

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Posted 15 October 2024 - 12:35 AM

Oe way to get the eyepiece near the primary is with a Nasmyth focus setup.  https://en.wikipedia...smyth_telescope




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