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Equipment Discussions >> Reflectors

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Astrojensen
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Reged: 10/05/08

Loc: Bornholm, Denmark
Re: What's the largest size amateur dob available? new [Re: turtle86]
      #5924834 - 06/17/13 03:28 AM

The problem with a scope this size is that an observatory is going to be incredibly expensive, simply because of the huge size and amount of material needed for its construction, not to mention the machinery and hours needed.


Clear skies!
Thomas, Denmark


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Jason D
Postmaster
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Reged: 10/21/06

Loc: California
Re: What's the largest size amateur dob available? new [Re: Astrojensen]
      #5924845 - 06/17/13 03:40 AM

Those who can afford a 70" reflector should not have any problem affording an observatory

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Astrojensen
Post Laureate
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Reged: 10/05/08

Loc: Bornholm, Denmark
Re: What's the largest size amateur dob available? new [Re: Jason D]
      #5924850 - 06/17/13 04:04 AM

I'm not so sure about that. We do tend to want to maximize aperture and totally forget everything else.

Also, making the scope portable and not needing an observatory can suddenly either cut the total price in more than half or almost double the available cash you can spend on aperture.

No matter how we look at it, observatories are expensive. And in many places, they require permittance and must follow building regulations, adding complexity. A domed observatory for a 40" f/5 scope is massively huge, the size of a normal family house.


Clear skies!
Thomas, Denmark


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careysub
Carpal Tunnel
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Reged: 02/18/11

Loc: Rancho Cucamonga, CA
Re: What's the largest size amateur dob available? new [Re: turtle86]
      #5924857 - 06/17/13 04:17 AM

I have thought that if you want to make a really huge Dob that it should be housed in a permanent observatory along the lines of the MMT on Mt. Hopkins:

http://www.hposoft.com/MMTImages/Observatory/ModelMMT.JPG

The entire structure rotates with the telescope (although the outer structure is isolated from the telescope mount) with clam shell doors covering the entire front. This allows a fixed elevator chair mechanism to provide easy seated viewing.

This could work even if the telescope itself is designed to be "mobile" (has wheels and can move). It would be rolled into the observatory and then secured rigidly in place.


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careysub
Carpal Tunnel
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Reged: 02/18/11

Loc: Rancho Cucamonga, CA
Re: What's the largest size amateur dob available? new [Re: Astrojensen]
      #5924859 - 06/17/13 04:21 AM

But you need a place to keep the giant mobile telescope anyway.

To some extent this is an unavoidable expense.

And you need to move it if it is to be really mobile - a huge trailer and a big truck, or else a U-Haul moving van, or similar.


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BluewaterObserva
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Reged: 05/18/04

Re: What's the largest size amateur dob available? new [Re: careysub]
      #5925847 - 06/17/13 04:07 PM

I have a 30" on a GEM in my obs. I thought I wanted a 1 meter, but the 30" really was already bite'n off more than I could really chew.

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robininni
scholastic sledgehammer


Reged: 04/18/11

Loc: Stephenville, TX
Re: What's the largest size amateur dob available? new [Re: BluewaterObserva]
      #5926464 - 06/17/13 10:19 PM

Quote:

I have a 30" on a GEM in my obs. I thought I wanted a 1 meter, but the 30" really was already bite'n off more than I could really chew.




Whoa! When I think 30" reflector, I immediately thing Dobsonian. That's got to be one heck of a GEM--an Orion Atlas no doubt?


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BluewaterObserva
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Reged: 05/18/04

Re: What's the largest size amateur dob available? new [Re: robininni]
      #5926627 - 06/17/13 11:38 PM

I believe it is one of the largest aperture scopes, GEM mounted, still in use in the world.

800lbs of counterweight on there by the way.

If your curious:
http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/4111141/page...

Edited by BluewaterObserva (06/17/13 11:41 PM)


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Bill Weir
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Reged: 06/01/04

Loc: Metchosin (Victoria), Canada
Re: What's the largest size amateur dob available? new [Re: BluewaterObserva]
      #5926752 - 06/18/13 01:39 AM Attachment (48 downloads)

This is the f/5 25" that I was out visiting tonight at the school observatory. I was supposed to be showing a visiting school group around the observatory but unfortunately the weather didn't cooperate. That metal tube is 9' long. Counter weights are in the 800lb range also.

Bill


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Bill Weir
Carpal Tunnel
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Reged: 06/01/04

Loc: Metchosin (Victoria), Canada
Re: What's the largest size amateur dob available? new [Re: Bill Weir]
      #5926756 - 06/18/13 01:42 AM Attachment (45 downloads)

This is what it looked like in the beginning before it was painted and Jack Newton was still dragging it around on a trailer to dark sites. This was before he donated it to the school.

Bill


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kfrederick
Carpal Tunnel
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Reged: 02/01/08

Re: What's the largest size amateur dob available? new [Re: Bill Weir]
      #5926876 - 06/18/13 06:28 AM

A 40 inch f3 the eyepiece is under 100 inches above the primary .The diameter is not the pain it is the length of the OTA A 39.4 inch supper max blank is not bad price .

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LivingNDixie
TSP Chowhound
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Reged: 04/23/03

Loc: Trussville, AL
Re: What's the largest size amateur dob available? new [Re: kfrederick]
      #5927394 - 06/18/13 12:05 PM

There are four 36in Obsessions in existance. One is owned my Larry Mitchell in Texas. One is owned by a guy in Birmingham Alabama. I don't know where the other two are. These scopes are massive.

Edited by LivingNDixie (06/18/13 12:07 PM)


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Pinbout
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Reged: 02/22/10

Loc: nj
Re: What's the largest size amateur dob available? new [Re: LivingNDixie]
      #5928354 - 06/18/13 10:19 PM

What about tom clarks 42? I'd like to look thru that scope since lockwood worked the mirror.

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FJA
Sketcher Extraordinaire
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Reged: 11/17/04

Loc: 50.65° N, 1.15° W
Re: What's the largest size amateur dob available? new [Re: LivingNDixie]
      #5965235 - 07/11/13 07:04 AM

Quote:

There are four 36in Obsessions in existance. One is owned my Larry Mitchell in Texas. One is owned by a guy in Birmingham Alabama. I don't know where the other two are. These scopes are massive.




I'm fairly (though not 100%) certain that a guy here in the UK has got one.


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George N
Carpal Tunnel
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Reged: 05/19/06

Loc: Binghamton & Indian Lake NY
Re: What's the largest size amateur dob available? new [Re: LivingNDixie]
      #5965610 - 07/11/13 12:21 PM

Quote:

There are four 36in Obsessions in existance. One is owned my Larry Mitchell in Texas. One is owned by a guy in Birmingham Alabama. I don't know where the other two are. These scopes are massive.




One Obsession 36 is (was?) owned by a guy in New Hampshire. He brought it to Stellafane 2 or 3 years, where I had a chance to look thru it and talk to the owner. Some other folks who know him have told me that he now has it in an observatory at his home.

I kept thinking of this scope as "Dobasaurus Rex"! It was huge. However, it was possible for one person to set up. Like the Obsession 30's, it is on wheels that are rotated out of the way when observing. It also cranks down after the truss poles are in place to hang the UTA on while standing on the ground. The owner had added a finder scope on an additional pole so that it could be used while standing on the ground. The 36 was transported in a trailer with a ramp backdoor, so to get it out, you just push it down the ramp. To get it back in the trailer, there was a small electric winch at the front of the trailer (powered by the tow vehicle's battery). Attach the cable to the scope - pull it up the ramp.

The owner told me that he was thinking of going back to a 20-inch, but he never did. He also said that owning a scope this size was "a lifestyle choice, like getting married or joining a monastery."

I've seen a number of other 28 to 32 inch Dobs that I consider designed to be easier to set up than the Obsession 36..... but that is a relatively old scope that now seems 'slow' at F/5.


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derangedhermit
Pooh-Bah


Reged: 10/07/09

Loc: USA
Re: What's the largest size amateur dob available? new [Re: JayinUT]
      #5965643 - 07/11/13 12:44 PM

Quote:

Anyway, Mike Clements is building and is almost done with his 70 inch reflector which is out at Steve Dobbs home/land. Here is a link to a post in February on that from my blog.



If my eyes do not deceive me, that's a 9-"point" (disc) cell.


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dan_h
Carpal Tunnel


Reged: 12/10/07

Re: What's the largest size amateur dob available? new [Re: kfrederick]
      #5965672 - 07/11/13 01:09 PM

Quote:

A 40 inch f3 the eyepiece is under 100 inches above the primary .The diameter is not the pain it is the length of the OTA A 39.4 inch supper max blank is not bad price .




I believe Kim Colter has a 40" Dob in a permanent home in Missouri. I don't know the f ratio.

dan


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Achernar
Postmaster
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Reged: 02/25/06

Loc: Mobile, Alabama, USA
Re: What's the largest size amateur dob available? new [Re: LivingNDixie]
      #5965676 - 07/11/13 01:11 PM

Massive does not begin to describe any 36-inch Dob, not when you see the eyepiece 15 feet above the ground. I've only seen one Dob in person that was that big. It was at the 2006 Okie-Tex starparty and to say the least it stood out among a forest of large Dobs that were on the site. Seeing how tall of a ladder was needed to reach the eyepiece, I opted not look through it. I work off of ladders and at heights for a living, I do not like climbing in the dark, not after falling off a ladder, not once but twice. In both case I was very lucky that I didn't get seriously hurt, or worse. I have heard of folks falling off a ladders while peering through big Dobs too.

Taras


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turtle86
Pooh-Bah Everywhere Else
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Reged: 10/09/06

Re: What's the largest size amateur dob available? new [Re: Pinbout]
      #5965696 - 07/11/13 01:26 PM

Quote:

What about tom clarks 42? I'd like to look thru that scope since lockwood worked the mirror.




It had great views even before Lockwood worked on the mirror. On one cold memorable night Thor's Helmet looked almost three dimensional with near photographic detail.


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TechPan6415
sage
*****

Reged: 07/29/12

Loc: Aspen, Co
Re: What's the largest size amateur dob available? new [Re: JayinUT]
      #5984581 - 07/22/13 02:44 PM

Quote:

Anyway, Mike Clements is building and is almost done with his 70 inch reflector which is out at Steve Dobbs home/land. Here is a link to a post in February on that from my blog.




That....is....
insane!

The largest scope I ever looked through was a 36" Coulter Optical monster at Riverside in the early 90's. I saw color in M8 and it was pretty memorable. I figure until I get a permanent home I am good with my 16", a 24"-30" might speak to me more clearly if I have an observatory to put it in.

But 70"...wow, I could not imagine what those views would be like.


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