steel tubing dobsonian?

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steel tubing dobsonian?

#1

Post by GCoyote »


Has anyone tried building a simple dob mount using these?

https://www.lowes.com/pd/Steelworks-1-i ... be/3049421

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It seems like I could just bolt it together and adjust the width between the uprights for more than one scope.

I didn't find a design online and have not gotten serious about working out the details yet. :geek:
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Re: steel tubing dobsonian?

#2

Post by Lady Fraktor »


I am sure it could be used for struts and supports reliablely though will be a bit heavier than aluminium.
See Far Sticks: Antares Elita 103/1575, AOM FLT 105/1000, Bresser BV 127/1200, Nočný stopár 152/1200, Vyrobené doma 70/700, Stellarvue NHNG DX 80/552, TAL RS100/1000, Vixen SD115s/885
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Re: steel tubing dobsonian?

#3

Post by helicon »


I had this idea of building a simple telescope with two struts holding the mirror cell (which would be made in a triangular shape to hold the mirror) one strut holding the focuser and secondary. With a strut holding up the telescope. A bit of a problem in designing a mount but I had kind of a fantasy of an Astroscan type ball which would sit on a base. Not much capability of moving effectively in altitude and azimuth as a traditional dob, but solid.

I made a few sketches but didn't come up with anything conclusive. I still think there's lots of opportunities to creatively build a telescope given that there only is a need for three elements to exist - a primary mirror, a secondary, and a focuser. A goal would be to make the rest of the structure "get out of the way".

Whomever comes up with the next cool simplistic design could become a very wealthy guy/gal. John Dobson created the dob for the most part but he just opened sourced the idea so it took over the market and he did not profit. (Well, he had been a monk anyway)

Think of Bill Gates buying the rudiments of MS-DOS from Seattle Software and licensing that to IBM!

Good luck and keep thinking of a design!
-Michael
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Re: steel tubing dobsonian?

#4

Post by Thefatkitty »


I've had a few ideas like this; one made it from the drawing table to reality with my 8" Skywatcher. 3/4" square steel tubing, was much lighter than the wood base... However, the problem was that it was too "tight"; if I touched the scope anywhere, it would almost vibrate.
Ever heard of "The Hum"? It may have been caused by me just touching this.... :lol:

Nov-11-2012_scope1.jpg
Nov-11-2012_scope2.jpg


All that said, I have to think wood is the best way to go. There has to be something to absorb the motion of turning it, and steel is just too rigid. Aluminum might be a nice "fine-line" but at what cost?

Anyways, just my two cents.

All the best, and would like to see what you come up with :D
Mark

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Too much Towa glass/mirrors.

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Re: steel tubing dobsonian?

#5

Post by GCoyote »


I don't have the space to store a large wooden mount so my goal is to create something I can take down by removing a few wing nuts for compact storage. Having multiple evenly spaced pre-drilled holes should allow me to adjust it for assorted conditions. And if all else fails, I can use the tubing for shelves. ;)
Any metaphor will tear if stretched over too much reality.
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Re: steel tubing dobsonian?

#6

Post by GCoyote »


I could reduce the weight by going with an angle iron instead of a square tube at the cost of some rigidity.

Either way, the pre-drilled holes are evenly spaced and accept the 5/16" mounting bolts for the OTA I plan to use. That way I'm not trying to do any precision drilling or cutting.

Fasten it to the plywood base with simple steel L or U brackets.

Image
Any metaphor will tear if stretched over too much reality.
Gary C

Celestron Astro Master 130mm f5 Newtonian GEM
Meade 114-EQ-DH f7.9 Newtonian w/ manual GEM
Bushnell 90mm f13.9 Catadioptric
Gskyer 80mm f5 Alt/Az refractor
Jason 10x50 Binoculars
Celestron 7x50 Binoculars
Svbony 2.1x42 Binoculars
(And a bunch of stuff I'm still trying to fix or find parts for.)
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Re: steel tubing dobsonian?

#7

Post by OzEclipse »


Square section aluminium tube is both light and rigid.

I recently purchased a second hand 12.5" f6 RF ROYCE conical mirror. Not in any rush to build but the ultimate goal is to design a very portable dob that can be broken down and packed into a compact sedan. I am 6 ft tall so the 12.5 "f6, if carefully constructed in a low profile mount should be at eye level when pointed near the zenith=>no ladders!

There are some general design rules that are a good guide :
  • If you are looking for maximum rigidity for smallest physical size, construct in steel.
    If you are looking for maximum rigidity for lightest weight size, construct in aluminium
    Hollow sections give maximum rigidity for weight in any material.
Once you ditch RHS and go to an angle section, you will lose a lot of rigidity.

good luck

Joe
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Re: steel tubing dobsonian?

#8

Post by gregl »


OzEclipse wrote: Fri Nov 22, 2019 12:10 pm ...

Once you ditch RHS and go to an angle section, you will lose a lot of rigidity.

...
Ditto. I would not use angle. Square al. tube would be an ideal choice. Light, easy to drill and cut, rust proof, can be made to look good. Avoid the hardware store extrusions and track down some 6061. The hardware store alloy (I don't know what it is) is often "sticky" and hard to work with; the 6061 machines well. Use WD40 or kerosene as a cutting fluid when cutting, drilling or tapping.
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Re: steel tubing dobsonian?

#9

Post by John Fitzgerald »


Tubing doesn't easily twist. Angle twists easily.
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Re: steel tubing dobsonian?

#10

Post by Marcelo F. »


GCoyote wrote: Sat Nov 09, 2019 3:35 pm I could reduce the weight by going with an angle iron instead of a square tube at the cost of some rigidity.

Either way, the pre-drilled holes are evenly spaced and accept the 5/16" mounting bolts for the OTA I plan to use. That way I'm not trying to do any precision drilling or cutting.

Fasten it to the plywood base with simple steel L or U brackets.

Image
The example you give there is a profile made for cable passage, was not made thinking of regidity. In mechanical construction usually the cheap become expensive in the medium term. A bespoke solution is always more expensive than a standard purchasing solution. If you are looking for modeling and rigidity use an aluminum profile like this:
Image
If you want something more compact you start entering the more expensive segment like carbon pipes and 3D printing.
Telescope: Dobson N 76/300 FirstScope DOB w/ DIY tripod adapter, 5x24 Finderscope.
Eps: 4mm Ramsden, 6mm Huygenian, 12.5mm Huygenian, 20mm Huygenian, 4mm Plossl, 10mm Plossl, 20mm Plossl, Barlow 2x, Barlow 3x, Barlow 5x, Solomark LP Filter, Dark Green Moon Filter.
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Re: steel tubing dobsonian?

#11

Post by GCoyote »


Well the, point of the project is to hold down the cost and have a mount I can disassemble by removing a very small number of bolts. Interesting material though.
Any metaphor will tear if stretched over too much reality.
Gary C

Celestron Astro Master 130mm f5 Newtonian GEM
Meade 114-EQ-DH f7.9 Newtonian w/ manual GEM
Bushnell 90mm f13.9 Catadioptric
Gskyer 80mm f5 Alt/Az refractor
Jason 10x50 Binoculars
Celestron 7x50 Binoculars
Svbony 2.1x42 Binoculars
(And a bunch of stuff I'm still trying to fix or find parts for.)
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Re: steel tubing dobsonian?

#12

Post by Lady Fraktor »


The square stock you originally posted will be much more rigid than the angle and should work out alright.
See Far Sticks: Antares Elita 103/1575, AOM FLT 105/1000, Bresser BV 127/1200, Nočný stopár 152/1200, Vyrobené doma 70/700, Stellarvue NHNG DX 80/552, TAL RS100/1000, Vixen SD115s/885
EQ: TAL MT-1, Vixen SXP, AXJ, AXD
Az/Alt: AYO Digi II/ Argo Navis, Stellarvue M2C/ Argo Navis
Tripods: Berlebach Planet (2), Uni 28 Astro, Report 372, TAL factory maple, Vixen ASG-CB90, Vixen AXD-TR102
Diagonals: Astro-Physics, Baader Amici, Baader Herschel, iStar Blue, Stellarvue DX, Takahashi prism, TAL, Vixen flip mirror
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Re: steel tubing dobsonian?

#13

Post by Marcelo F. »


Here is an example using aluminum profile:
https://www.youtube.com/watch?v=wUpII_wUk7U
Telescope: Dobson N 76/300 FirstScope DOB w/ DIY tripod adapter, 5x24 Finderscope.
Eps: 4mm Ramsden, 6mm Huygenian, 12.5mm Huygenian, 20mm Huygenian, 4mm Plossl, 10mm Plossl, 20mm Plossl, Barlow 2x, Barlow 3x, Barlow 5x, Solomark LP Filter, Dark Green Moon Filter.
Binoculars: Bresser National Geographic 7x50, Omegon Nightstar 20x80
Camera: none
Messier: 7/110
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