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How much does your dob weigh per inch of aperture?

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#26 nicknacknock

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Posted 02 April 2013 - 05:46 AM

Ultralight dobs have come a long way, but of course some compromises are made in the design to accommodate the required weight limit. It's the old plate armor Vs bullets theory in a twisted kind of way :cool:

#27 azure1961p

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Posted 02 April 2013 - 06:13 AM

8 lbs.per inch.

Pete

#28 azure1961p

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Posted 02 April 2013 - 06:17 AM

Lol yeah but it's got MMMAASSSSS.

Pete

#29 Mike B

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Posted 02 April 2013 - 11:40 AM

That's an excellent compilation, Carey! :bow: Thanks for pulling that up from the archives- i'll happily add my Dob to the data:

StarSplitter-15....... 15" ..... 112# ..... 7.47#/" .... 0.50#/"2
... that's structure+glass, no accessories. Adding the battery for the fan & DobDriver is an additional ~6#.

Way to much.... Wood adds up quicker than I expoected.


It's a beast, fersure, toward the robust end of the range- lots of beautiful plywood, stained & varnished... yet maybe not such a bad price to pay for getting a scope capable of doubling as "furniture" for the spousal unit. ;)

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#30 careysub

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Posted 02 April 2013 - 02:04 PM

Yours too can be weightless - for a bit - if you choose to drop it off a roof.

#31 Starman1

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Posted 02 April 2013 - 05:42 PM

My Teeter is 6.5 lbs/inch, without eyepiece, Paracorr, shroud, or light shield.

#32 John Huntley

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Posted 02 April 2013 - 06:47 PM

My Orion Optics solid tube 12" F/5.3 on its custom dob mount weighs around 60 lb all in so 5 lb per inch. That includes a Rigel Quikfinder and an 8x50 RACI finder.

#33 GeneT

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Posted 02 April 2013 - 08:07 PM

12.5 inch Portaball, 65lbs, = 5.2lbs an inch--the easiest 65 pounds I have ever lifted! :jump:

#34 mconnelley

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Posted 03 April 2013 - 02:04 AM

Hello:

My 20" is about 80 lbs., yielding 4 lbs/in or 0.25 lbs/in^2 of collecting area.

Cheers
Mike

#35 Tom Clark

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Posted 03 April 2013 - 07:24 AM

My 16 weighs 68 lbs, so 4.25 pounds per inch, Too bad the mirror weighs 28 pounds or it would be a lot lighter.

The 24 weighs 160 pounds, for 6.66 p/in. Still pretty light for a bigger scope.

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#36 JKoelman

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Posted 03 April 2013 - 08:25 AM

... another measure might be pounds/square inch, the weight for a given amount of light gathering.

Indeed, lb/inch ratios are less meaningful. I would advocate the square inch per pound ratio which tells me how much light gathering I get for the weight I have to lug around.

For a given telescope design, the inch^2/lb ratio drops to zero for very small apertures and also for very large apertures. The first effect is due to focuser weight and all other weights not directly contributing to the light gathering starting to dominate, and the latter effect is due to the mass scaling faster than quadratically with the linear size (as remarked by Jon).

So a given scope design must reachs a maximum in light gathering per pound of weight at a certain specific aperture.

Recently I inventorised square aperture/weight ratios for refractors, cats and Newtonians. I excluded the mount and considered OTA weight only.

For designs like the Orion XT, the square inch per pound ratio reaches a maximum of 3.1 for 10" of aperture. Lightweight dob designs tend to reach 4.5, and so does a miniature dob like the Starblast 4.5. For CAT's the same value of 4.5 inch^2/lb is reached for 8" of aperture (C8). Refractors tend to render less than 2 square inches per pound of weight. Even the AP Stowaway, generally considered a marvel in compactness, scores no higher than 2.0. Notable exception are fast achromats, with the ST-80 reaching a value of 3.4 and the Stellarvue F80 reaching a reflector-like score of 4.5.

The end conclusion is that no matter the design (refractor, reflector or cat) the lightest amateur telescopes reach a light/weight ratio of around 4.5 sq.inch/lb.

Which means our toys beat any large professional instrument, including the Hubble Space Telescope (0.4 inch^2/lb), hands down. :grin:

#37 dscarpa

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Posted 03 April 2013 - 10:16 AM

Too much. Because it's a F/5 with SIPS and a 60mm finder I'm having the base of my 11" Teeter STS made extra heavy so hopefully it doesn't end up being tippy. David

#38 ctcables

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Posted 15 August 2013 - 04:26 AM

My new 20inch OTA is 69lbs, very happy with it. 3.5lbs

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#39 mnev326

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Posted 15 August 2013 - 07:26 AM

Tom,

Your 16 is quite light for its aperture. I have a Tectron 15 built I think in 1991. I would guess it weighs in at about 100lbs, which comes out to 6.67lbs per inch.

Mark

#40 csrlice12

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Posted 15 August 2013 - 07:53 AM

My new 20inch OTA is 69lbs, very happy with it. 3.5lbs


I'd be more impressed if you were juggling more than one..... :lol:

#41 Jeff Bennett

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Posted 15 August 2013 - 05:38 PM

My 11 inch Teeters STS solid tube dob is 43 lbs, including base, tube and tube cradle, or 4 lbs/inch.

Jeff

#42 John Huntley

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Posted 15 August 2013 - 05:42 PM

My Orion Optics 12" F/5.3 dob is 58 lbs in total so 4.8 lbs per inch.

#43 derangedhermit

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Posted 15 August 2013 - 05:50 PM

I think this is fantastic. I do agree the in^2/lb (or equivalent in SI units) is the right measurement. I hope this gets put in a spreadsheet.

Last comment: I think mirror thickness may have a significant impact, so please consider adding that info. Mirror diameter and thickness, weight of total telescope (not just OTA, although OTA and mount separately would be interesting too.)

#44 george golitzin

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Posted 15 August 2013 - 06:33 PM

My 10-inch weighs 35 pounds, so 3.5 lb/in. The photo shows it back when it was f/5.6; it's f/5 now.

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#45 george golitzin

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Posted 15 August 2013 - 06:34 PM

here it is all packed up.

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#46 george golitzin

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Posted 15 August 2013 - 06:36 PM

My new 20inch OTA is 69lbs, very happy with it. 3.5lbs


That's fabulous for a 20-inch--congratulations on your build!

#47 ctcables

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Posted 15 August 2013 - 07:26 PM

Thank You George, it was a lot of work. I am so pleased with the balance as well. No extra weight need and I can use any eyepiece smallor large wwith or without barlow. M101 pinwheel looks great as well. I could never see the detail in my 14.75 inch that I can see with my new 20inch by 1inch thick quartz mirror.

#48 dan777

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Posted 16 August 2013 - 01:14 PM

Orion XT8g: 52.4 / 8 = 6.55 lb/inch

#49 Jeff Porter

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Posted 16 August 2013 - 08:52 PM

I decided to go with weight/aperture^2.

Here is what we have so far:

Scope--------------------Aperture---Weight---LB/Aperture^2
ctcables 14.5------------14.5-------32-------0.152
ctcables 20--------------20---------69-------0.173
mconnelley 20------------20---------80-------0.200
Hubble Optics UL18-------18---------72-------0.222
Hubble Optics UL16-------16---------60-------0.234
Hubble Optics UL14-------14---------48-------0.245
Tom Clark 16------------16---------68-------0.266
Tom Clark 24------------24---------160------0.278
Webster D18--------------18---------92-------0.284
Dobstuff 17.5------------17.5-------89-------0.291
Obsession 20 UC----------20---------124------0.310
StarStructure TL 17.5----17.5-------96-------0.313
Obsession 18 UC----------18---------105------0.324
omahaastro 30-----------30---------300------0.333
Mirzam 14---------------14---------68-------0.347
george golitzin 10------10---------35-------0.350
Obsession 15 UC----------15---------79-------0.351
Jon Isaacs 16 Dobstuff--16---------90-------0.352
Teeters STS 11----------11---------43-------0.355
Dobstuff 14--------------14---------70-------0.357
Obsession 20 Classic-----20---------147------0.368
Obsession 18 Classic-----18---------126------0.389
Starmaster 20------------20---------156------0.390
StarStructure TL 15------15---------88-------0.391
Obsession 15 Classic-----15---------89-------0.396
tezster 10 Dobstuff-----10---------40-------0.400
Orion Optics 12 f/5.3---12---------58-------0.403
Obsession 12.5 Classic---12.5-------65-------0.416
Portaball 12.5-----------12.5-------65-------0.416
Starmaster 18------------18---------138------0.426
1991 Tectron 15----------15---------100------0.444
Starmaster 14.5----------14.5-------96-------0.457
Project Galileo LB16-----16---------120------0.469
Starmaster 16------------16---------121------0.473
Zhumell 16---------------16---------121------0.473
StarStructure TL 12.5----12.5-------78-------0.499
Meade LB 16--------------16---------128------0.500
Starman1 12.5 Teeter----12.5-------81-------0.518
Zhumell 12---------------12---------75-------0.521
Starsplitter 15----------15---------118------0.524
Jason Comet Hunter 480---3----------4.75-----0.528
Orion XT10---------------10---------53-------0.530
Achernar 15-------------15---------120------0.533
FirstSight---------------12---------80-------0.556
Meade LB 12--------------12---------80-------0.556
JimMo 14.5--------------14.5-------120------0.571
isawit 12---------------12---------86.1-----0.598
Zhumell 10---------------10---------60-------0.600
Orion XX12---------------12---------86.5-----0.601
Ed D 6 Strut------------6----------22-------0.611
Starmaster 11------------11---------74-------0.612
Orion XX14i--------------14---------120------0.612
Meade LB 10--------------10---------65-------0.650
Tad S XT8i---------------8----------42-------0.656
Orion XX16G--------------16---------195------0.762
Orion XT8G---------------8----------52.4-----0.819
Ed D 6------------------6----------30-------0.833
Coulter 13.1------------13.1-------150------0.874
Orion XT6i---------------6----------35-------0.972
Azure1961p---------------8----------64-------1.000
Horsetrain Cave----------12.5-------350------2.240

#50 ctcables

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Posted 22 June 2014 - 04:25 AM

new winner. ultralight 21" 55lbs
http://www.cloudynig...Board=atm&Nu...






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