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Equipment Discussions >> ATM, Optics and DIY Forum

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Chuck Hards
Post Laureate
*****

Reged: 05/03/10

Loc: The Great Basin
70 inch Dob sneak peek
      #6146228 - 10/19/13 08:49 AM

I'm headed over to take a look through it tonight. He built it in Steve's outbuilding at Nova Optical. I want to get there early enough to get some photos. This is a story by a local TV station, aired last night:

http://www.ksl.com/?sid=27301024&nid=148&title=utahn-sets-record-by-b...


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Sean Cunneen
Let Me Think
*****

Reged: 08/01/07

Loc: Blue Island Illinois
Re: 70 inch Dob sneak peek new [Re: Chuck Hards]
      #6146264 - 10/19/13 09:20 AM

That is fantastic! Can you ask what he meant by the line "put the reflective coating on with a weed sprayer"??? That line made me gasp

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Chuck Hards
Post Laureate
*****

Reged: 05/03/10

Loc: The Great Basin
Re: 70 inch Dob sneak peek new [Re: Sean Cunneen]
      #6146267 - 10/19/13 09:23 AM

The mirror is too large for Steve's vacuum chamber, so they are silvering it, using a spray-on process. It works well, though must be renewed periodically due to oxidation.

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Chuck Hards
Post Laureate
*****

Reged: 05/03/10

Loc: The Great Basin
Re: 70 inch Dob sneak peek new [Re: Chuck Hards]
      #6146327 - 10/19/13 10:10 AM

29-inch secondary! Can't recall the size of the tertiary but it's relatively small. Welded steel structure. I'll get more details tonight.

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Jeff Morgan
Postmaster
*****

Reged: 09/28/03

Loc: Prescott, AZ
Re: 70 inch Dob sneak peek new [Re: Chuck Hards]
      #6146402 - 10/19/13 10:49 AM

A tertiary mirror?!

He's losing light!!!!!!!!!!!!



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Chuck Hards
Post Laureate
*****

Reged: 05/03/10

Loc: The Great Basin
Re: 70 inch Dob sneak peek new [Re: Jeff Morgan]
      #6146442 - 10/19/13 11:09 AM

If configured as a standard Newt, the observer would be over 4 storey's high. By folding it, you "only" need to climb a 2-storey tall ladder. I'm going prepared for nose bleeds.

This will be interesting. I talked to him last week and he said at his lowest power, it took 3 fields to traverse M42. We are working on a lower power eyepiece together and he's making a large-diameter focuser to accomodate it. Something like 4". I'm taking him the focuser bearings tonight.


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Chuck Hards
Post Laureate
*****

Reged: 05/03/10

Loc: The Great Basin
Re: 70 inch Dob sneak peek new [Re: Chuck Hards]
      #6146858 - 10/19/13 03:01 PM

This is funny- at least 2 other people have posted links to the local news story in other forums, since I first posted this early this morning.

News is spreading! Mike's going to have lines forming soon.

"Build it, and they will come."


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MikeMcCaskey
professor emeritus


Reged: 03/09/12

Loc: South Central Kansas
Re: 70 inch Dob sneak peek new [Re: Chuck Hards]
      #6146872 - 10/19/13 03:09 PM

WOW!

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christheman200
sage


Reged: 06/12/13

Loc: Toronto, Canada
Re: 70 inch Dob sneak peek new [Re: MikeMcCaskey]
      #6146983 - 10/19/13 04:22 PM

This really gave me a kick in the butt to get going on my 12" dob, if he can do that, I can build a 12" dob.

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Mirzam
Post Laureate
*****

Reged: 04/01/08

Loc: Lovettsville, VA
Re: 70 inch Dob sneak peek new [Re: MikeMcCaskey]
      #6146987 - 10/19/13 04:24 PM

There is skepticism from one individual locally (here) that the mirror will produce an acceptable focus under gravity loading since it was originally designed to be used in zero G.

Curious what may have been done regarding mirror testing and support aspects, especially with Steve Dodds involved.

JimC


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Scott in NC
Mad Hatter
*****

Reged: 03/05/05

Loc: NC
Re: 70 inch Dob sneak peek new [Re: Mirzam]
      #6147042 - 10/19/13 05:01 PM

Pretty cool! I'd love to get a look through that (but then, who wouldn't?).

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tim53
Postmaster
*****

Reged: 12/17/04

Loc: Highland Park, CA
Re: 70 inch Dob sneak peek new [Re: Scott in NC]
      #6147121 - 10/19/13 05:27 PM

I think I'd be tempted to put a camera at the Newt focus and save money by not buying a secondary or tertiary. Or ladder, for that matter!

I'd have to put a drive on it, though.

-Tim.


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Pinbout
Postmaster
*****

Reged: 02/22/10

Loc: nj
Re: 70 inch Dob sneak peek new [Re: tim53]
      #6147199 - 10/19/13 06:06 PM

how far away do you have to be to KE test that mirror.

4 story to focus, 8 story to coc. 8x15' = 120'


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mikey cee
Postmaster
*****

Reged: 01/18/07

Loc: bellevue ne.
Re: 70 inch Dob sneak peek new [Re: Pinbout]
      #6147251 - 10/19/13 06:46 PM

That's all you dob owners would need. You'd ditch your 20"+ dobs in a heartbeat and become totally bummed out. Mike

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DavidinFL
super member
*****

Reged: 08/28/09

Loc: Navarre, FL
Re: 70 inch Dob sneak peek new [Re: mikey cee]
      #6147290 - 10/19/13 07:08 PM

That's incredible! He needs to publish a schedule of where he'll be so folks can come see it when he goes on tour.

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Pinbout
Postmaster
*****

Reged: 02/22/10

Loc: nj
Re: 70 inch Dob sneak peek new [Re: Chuck Hards]
      #6147362 - 10/19/13 07:53 PM

Boy I see more of a jmi focuser then the scope...

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northernontario
Pooh-Bah
*****

Reged: 07/01/09

Loc: Porcupine, Ontario Canada
Re: 70 inch Dob sneak peek new [Re: Pinbout]
      #6147500 - 10/19/13 10:03 PM

I hope he brings that thing to Canada...

My backyard preferably.....

jake


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Pinbout
Postmaster
*****

Reged: 02/22/10

Loc: nj
Re: 70 inch Dob sneak peek new [Re: northernontario]
      #6147577 - 10/19/13 10:46 PM

Start singing the news...NY...NY.

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Chuck Hards
Post Laureate
*****

Reged: 05/03/10

Loc: The Great Basin
Re: 70 inch Dob sneak peek new [Re: Pinbout]
      #6147652 - 10/19/13 11:41 PM

I have just returned from Nova Optical, where the 70-inch scope is set up.

It's for real, folks. Steve, Mike, Charlie and I spent a couple of hours looking through high, thin cirrus but got some decent views of the core of M-31 as well as one of the best views of M-13 I've ever had, despite a bright, full moon and high haze.

Stars are perfectly round, there is no detectable astigmatism.

Even at nearly a ton total weight, it is still aimable by hand.

Wow, what a sight to behold.

Mike did say that he plans to take the scope on the road and hit as many major star-parties as his work schedule and budget will allow. He still has to pick up a trailer for the scope. It takes a full day to assemble once on-site.

The scope is going to remain operational through the winter at Nova Optical and Mike will operate it as his work schedule and the weather allow.

Steve seems to think that the silvered surfaces may only need to be renewed once a year. The current coating is a few months old and I could see no evidence of darkening (of course a visual inspection doesn't mean that reflectivity hasn't dropped, but it's encouraging).

I took a bunch of photos, including some close-ups of a few details and will post them tomorrow after I upload and process the ones that turned out.


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miniventures
Something Else
*****

Reged: 09/13/03

Loc: Powell Butte, Central Oregon
Re: 70 inch Dob sneak peek [Re: Chuck Hards]
      #6147743 - 10/20/13 01:16 AM

Nothing short of incredible. Congrats to Mike for the foresight and perseverance!

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