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Equipment Discussions >> Reflectors

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Achernar
Postmaster
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Reged: 02/25/06

Loc: Mobile, Alabama, USA
Re: How much does your dob weigh per inch of aperture? new [Re: Jeff Porter]
      #5771900 - 04/01/13 10:43 PM

Just by itself, my 15-inch is about 90lbs, or about 6 pounds per inch of aperture, throw in the batteries and other stuff in, or on the base, it's closer to 120lbs or 8 pounds per inch of aperture.

Taras


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Datapanic
Post Laureate
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Reged: 10/17/09

Loc: Tucson, Arizona
Re: How much does your dob weigh per inch of aperture? new [Re: Achernar]
      #5771923 - 04/01/13 10:58 PM

I don't own a Dobsonian, but thought I would blurt out the weight of the Horsetrail Cave Newtonian, just for comparison:

OTA: 130lbs
Dec Shaft Counterweights: 100lbs
Equitorial Mount/Stand: ~120lbs

It has wheels.


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omahaastro
sage


Reged: 08/30/06

Loc: Omaha, NE
Re: How much does your dob weigh per inch of aperture? new [Re: Datapanic]
      #5772055 - 04/02/13 01:05 AM

My 30" weighs about 300 lbs. It has a full thickness Sitall primary. It weighs about 70 lbs at the wheel barrel handles, which can make for an adventure going up/down the trailer ramp. I hope to implement some kind of winch solution somewhere between now and before my back goes out.

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Jeff Porter
super member
*****

Reged: 09/03/10

Loc: Utah
Re: How much does your dob weigh per inch of aperture? new [Re: kfrederick]
      #5772148 - 04/02/13 04:16 AM

Quote:

The HST is weightless so it wins






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Jeff Porter
super member
*****

Reged: 09/03/10

Loc: Utah
Re: How much does your dob weigh per inch of aperture? new [Re: Jeff Porter]
      #5772153 - 04/02/13 04:28 AM

I really appreciate all of the responses. Some of the ultralight designs are very impressive. My good friend Jay has a 14" Dobstuff that is smaller and lighter than my 12". The mirror box or my 17.5 is just barely too big to fit into my Honda Accord, so I haul that one around in my Odyssey.

Maybe I'll have an ultralight one day. This thread really shows the efficiencies that some are able to attain.

Jeff P.


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nicknacknock
professor emeritus
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Reged: 02/20/12

Loc: In a galaxy far far away...
Re: How much does your dob weigh per inch of aperture? new [Re: Jeff Porter]
      #5772219 - 04/02/13 06:46 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

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azure1961p
Postmaster
*****

Reged: 01/17/09

Loc: USA
Re: How much does your dob weigh per inch of aperture? new [Re: kfrederick]
      #5772241 - 04/02/13 07:13 AM

8 lbs.per inch.

Pete


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azure1961p
Postmaster
*****

Reged: 01/17/09

Loc: USA
Re: How much does your dob weigh per inch of aperture? new [Re: kfrederick]
      #5772244 - 04/02/13 07:17 AM

Lol yeah but it's got MMMAASSSSS.

Pete


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Mike B
Starstruck
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Reged: 04/06/05

Loc: shake, rattle, & roll, CA
Re: How much does your dob weigh per inch of aperture? new [Re: careysub]
      #5772849 - 04/02/13 12:40 PM Attachment (12 downloads)

That's an excellent compilation, Carey! 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#.

Quote:

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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careysub
Carpal Tunnel
*****

Reged: 02/18/11

Loc: Rancho Cucamonga, CA
Re: How much does your dob weigh per inch of aperture? new [Re: kfrederick]
      #5773110 - 04/02/13 03:04 PM

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

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Starman1
Vendor (EyepiecesEtc.com)
*****

Reged: 06/24/03

Loc: Los Angeles
Re: How much does your dob weigh per inch of aperture? new [Re: careysub]
      #5773668 - 04/02/13 06:42 PM

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

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John Huntley
scholastic sledgehammer
*****

Reged: 07/16/06

Loc: South West England
Re: How much does your dob weigh per inch of aperture? new [Re: Starman1]
      #5773828 - 04/02/13 07:47 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.

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GeneT
Ely Kid
*****

Reged: 11/07/08

Loc: South Texas
Re: How much does your dob weigh per inch of aperture? new [Re: Jeff Porter]
      #5774061 - 04/02/13 09:07 PM

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

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mconnelley
sage


Reged: 03/14/06

Loc: Hilo, HI
Re: How much does your dob weigh per inch of aperture? new [Re: GeneT]
      #5774662 - 04/03/13 03:04 AM

Hello:

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

Cheers
Mike


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Tom Clark
professor emeritus
*****

Reged: 11/14/07

Loc: North of Deming, NM
Re: How much does your dob weigh per inch of aperture? new [Re: mconnelley]
      #5774845 - 04/03/13 08:24 AM Attachment (14 downloads)

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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JKoelman
professor emeritus


Reged: 05/16/11

Loc: Bangalore, India
Re: How much does your dob weigh per inch of aperture? new [Re: Jon Isaacs]
      #5775000 - 04/03/13 09:25 AM

Quote:

... 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.


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dscarpa
Post Laureate
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Reged: 03/15/08

Loc: San Diego Ca.
Re: How much does your dob weigh per inch of aperture? [Re: Jeff Porter]
      #5775304 - 04/03/13 11:16 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

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ctcables
professor emeritus


Reged: 11/14/06

Loc: Oregon
Re: How much does your dob weigh per inch of aperture? new [Re: dscarpa]
      #6026513 - 08/15/13 05:26 AM Attachment (9 downloads)

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

Edited by ctcables (08/15/13 07:43 AM)


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mnev326
member


Reged: 02/06/07

Re: How much does your dob weigh per inch of aperture? new [Re: Tom Clark]
      #6026647 - 08/15/13 08:26 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


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csrlice12
Postmaster
*****

Reged: 05/22/12

Loc: Denver, CO
Re: How much does your dob weigh per inch of aperture? new [Re: ctcables]
      #6026689 - 08/15/13 08:53 AM

Quote:

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




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


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