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Newton or Dobson

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#1 Frank2

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Posted 15 February 2024 - 08:55 PM

I was out last night with my 16" dobsonian. Dew started condensing on my secondary. I looked down at the primary and it looked ok. Then I thought, the light bounces off the primary and is directed to the eyepiece by the secondary. This revolutionary design used to be called a newtonian after it's genious inventor. So I thought, why is this telescope now referred to as a dobsonian? Not even a Newtdob, or Dobnewt. Newton's legacy has been completly removed from the telescope he invented. Is the reason for the name change due to John Dobson putting the newtonian on a mount that can be effortlessly pointed in any direction? That does not seem a reasonable justification for replacing Newton's recognition for Dobson's. Especially, in light of the fact that Newton's original ball mount design did exactly that too. It seems that the adjective newtonian is now reserved for mostly outdated telescopes such as the Criterion RV-6 Dynascope and other solid tube scopes from the 60's. I understand that John Dobson's mount put large aperature scopes in the hands of many, and he was alive and Newton was long dead, but now that they are both gone is it time to regain some perspective?
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#2 Dan Watt

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Posted 15 February 2024 - 09:01 PM

John Dobson felt the same way. He hated the term dobsonian and would call them "newtonians on an alt-az mount". 


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#3 siriusandthepup

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Posted 15 February 2024 - 09:31 PM

When I grew up in the 50s and 60s - No one owned a 12.5" telescope unless you were a university or a very wealthy individual.

 

A good amateur telescope was a 6" Newt or a 2.4" or 3" refractor. I couldn't afford any of these growing up. My high school was lucky to own an RV-6 Newtonian.

 

Big telescopes were expensive and heavy! Definitely not portable.

 

In the late 60s/early 70s the "Dobsonian" revolution happened. Yes - John Dobson hated that we named the style of telescope after him. He was a modest individual with a profound love of the skies and sharing it with everyone.

 

He made large mirrors (8, 10, 12, 16, 24) using salvaged porthole glass (typically 1inch thick and fine annealed). He then used cardboard concrete form tubes for the tubes, made spiders from strips of wood, mirror cells and the rest of the telescope from plywood. The Dobsonian featured a simple push to point Altitude / Azimuth system that rode on friction bearings consisting of teflon pads riding on Ebonystar kitchen counter top material. The result was - large telescopes were affordable to the unwashed masses (us).

 

Not an evolution - a true revolution for astronomy lovers.

 

No disrespect at all for Mr. Newton. His design lasted almost unchanged for a couple hundred years.

 

Then came John Dobson to show us the next step. He is the reason you and many other of your fellow astronomers own 16" telescopes. We owe him a debt of gratitude.

 

waytogo.gif

 

And he spent a lot of time teaching the rest of us how to make 'em too!


Edited by siriusandthepup, 15 February 2024 - 09:32 PM.

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#4 maroubra_boy

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Posted 15 February 2024 - 09:43 PM

+1 Ed.

 

What he said.



#5 NinePlanets

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Posted 15 February 2024 - 10:03 PM

The optical system is STILL a Newtonian type.

 

The low-impact construction methods of John Dobson made inexpensive large Newtonians easy for anyone.

 

I NEVER refer to a Newtonian telescope as a Dobsonian. He didn't invent it. But I do give credit where due. An alt-az Newtonian constructed with the Dobsonian mindset is an idea that took the stargazing community by storm!


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#6 TOMDEY

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Posted 15 February 2024 - 10:35 PM

"Dobsonian" is a whimsical play on words (implicit nod to Newton) that also gives John well-deserved credit for substantially perfecting and popularizing the humble yet profoundly effective approach to large, buildable and utilitarian Newtonian telescope structures. That in no way discredits Isaac's accomplishment, and was never meant to. Sometimes we guys look for sources or righteous indignation --- where none exist. Both men exuded genius... maybe at different levels and in different ways --- but both deserving recognition. Calling my mass-produced car a Chevrolet doesn't somehow discredit Henry Ford.   Tom


Edited by TOMDEY, 15 February 2024 - 10:35 PM.

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#7 JohnTMN

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Posted 16 February 2024 - 02:17 AM

I was out last night with my 16" dobsonian.

Well ya really weren't.

You were out with your Newt, on a DOB base.

I was out with my 6" newt eq,,

flowerred.gif


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#8 Jon Isaacs

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Posted 16 February 2024 - 03:37 AM

"Dobsonian" refers to the mount. There are refractors and even SCTs on Dobsonian mounts.

 

Jon


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#9 csa/montana

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Posted 16 February 2024 - 04:54 AM

Moved to Reflectors, as Gen. Observing is NON equipment discussion.



#10 Illinois

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Posted 16 February 2024 - 07:25 AM

In 1950’s and 1960’s. 6 inch reflector is big telescope because of mount. I remember that my first real telescope is 1975 Edmund 6 inch f8 with metal mount. I take two trips to my backyard. It’s heavy.  Thanks to John Dobson invited box mount that today we can have as large as 36 inch! My 16 inch dobsonian is big but image that size of 16 inch would  require bigger mount in 1950’s! 
Dobsonian is telescope with alt az box while Newtonian is mount.  I remember in 1970’s. Brand name Parker selling 16 inch with mount. It’s big telescope and require observatory! 


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#11 rjacks

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Posted 16 February 2024 - 10:17 AM

It was Dobson's idea on mounting that made large Newtonians accessible to amateur astronomers. So, I think there is a real practical distinction between a 6 inch Newt on a tripod and 8 - 34 inch Newtonians on Dobson mounts. The genius of the big Newts on Dobsonian mounts merits its own recognition. I say this as someone who is awed by my 16 inch dobsonian every time I look through it. It's a wonder that this giant telescope is easy to set up and use. 


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#12 vtornado

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Posted 16 February 2024 - 11:09 AM

When I take my gear to a star party ...

  • If it's a 6 inch f/5 on a tripod its a "newt".
  • If its a 12 f/5 on a lazy susan its a "dob"
  • If its a 10 inch f/7 on a pier eq mount (it doesn't go, its too big) lol.gif

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#13 David Knisely

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Posted 16 February 2024 - 04:23 PM

"Dobsonian" refers to the mount. There are refractors and even SCTs on Dobsonian mounts.

 

Jon

Well, I'm afraid I might take issue with that, as the mount is just an altazimuth.  A Dobsonian is a simple Newtonian OTA on a simple 2-arm altazimuth mount (most often with open-faced gravity-constraint altitude bearings).  If people see a big refractor on such a simple open-faced altitude bearing altazimuth mount, people don't call it a "Dob", but a refractor.  Indeed, Dave Kriegie and Richard Berry's book, "The Dobsonian Telescope" doesn't even mention any optical configurations other than the Newtonian.  My 9.25 inch Schmidt-Cassegrain sits on its 2-armed fork altazimuth mount when running in the altazimuth mode, yet it is still called an SCT.  Oh yea, you could put an SCT OTA on such an open-faced altazimuth mount, but it remains an SCT.  Clear skies to you.


Edited by David Knisely, 17 February 2024 - 02:25 PM.

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#14 Keith Rivich

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Posted 16 February 2024 - 08:00 PM

I like the two terms. If one were to tell me they have a 10" Dob I know exactly what they have. But if they say "I have a 10" Newt" I have to ask what kind of mount is it on. 


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#15 Echolight

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Posted 16 February 2024 - 09:27 PM

Why didn't you say you were out with your 16 inch newtonian then?



#16 Jon Isaacs

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Posted 17 February 2024 - 07:07 AM

Well, I'm afraid I might take issue with that, as the mount is just an altazimuth.  A Dobsonian is a simple Newtonian OTA on a simple 2-arm altazimuth mount (most often with open-faced gravity-constraint altitude bearings).  If people see a big refractor on such a simple altazimuth mount, people don't call it a "Dob", but a refractor.  Indeed, Dave Kriegie and Richard Berry's book, "The Dobsonian Telescope" doesn't even mention any optical configurations other than the Newtonian.  My 9.25 inch Schmidt-Cassegrain sits on its 2-armed fork altazimuth mount when running in the altazimuth mode, yet it is still called an SCT.  Oh yea, you could put an SCT OTA on such an open-faced altazimuth mount, but it remains an SCT.  Clear skies to you.

 

It seems that people who own refractors and/or SCTS on Dobsonian style mounts call them refractors/SCTs on a Dobsonian style mount.

 

https://www.cloudyni...for-refractors/

 

A Dobsonian mount is a specific type of ALT-AZ mount, just any old alt-az mount does not necessarily qualify. 

 

Here is a Newtonian on an Alt-Az mount.. It's not a Dob. 

 

5901459-SpaceProbe 130ST ALT-AZ at the Starpad.JPG
 
Jon

Edited by Jon Isaacs, 17 February 2024 - 07:07 AM.

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#17 TayM57

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Posted 17 February 2024 - 11:35 AM

Yeah a Newtonian refers to the optical design, or, to be precise, the arrangement of two mirrors, a spherical, and a flat, to produce a focal plane.

 

A dobsonian is a broad term that encompasses the Newtonian optical design with a alt-az mount design. 


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#18 David Knisely

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Posted 17 February 2024 - 12:05 PM

 

It seems that people who own refractors and/or SCTS on Dobsonian style mounts call them refractors/SCTs on a Dobsonian style mount.

 

https://www.cloudyni...for-refractors/

 

A Dobsonian mount is a specific type of ALT-AZ mount, just any old alt-az mount does not necessarily qualify. 

 

Here is a Newtonian on an Alt-Az mount.. It's not a Dob. 

 

 
 
Jon

 

Yes, but you missed my point.  I don't call my 9.25 inch SCT an "SCT on an altazimuth mount".  I call it an SCT, period.  The term "Dobsonian" originally referred to John Dobson's 1970's and 80's creations of large home-brew solid tube (Sonotube) plate-glass mirror Newtonians with simple sling-type primary mirror supports with the OTAs mounted in open-faced bearing wooden altazimuth mounts (i.e. rocker box and ground board).  The term, by itself, has somewhat evolved to refer to a Newtonian on a simple open-faced altazimuth mount and does not refer to the mount itself.  In my log book, when using my 14 inch Dobsonian, I usually identify the instrument as a 14" f/4.6 Newtonian (mostly out of habit from years earlier when I had 8 inch and 10 inch Newtonians on equatorial mounts.  However, when mentioning it to other people, it's a" Dob", which people then almost instantly know what kind of instrument setup it is.  Clear skies to you.


Edited by David Knisely, 17 February 2024 - 02:28 PM.

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#19 Echolight

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Posted 17 February 2024 - 12:11 PM

To be a dob, it's gotta have a ground board.


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#20 therealdmt

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Posted 17 February 2024 - 12:18 PM

The way I remember it, it’s like TomDey said, that it was kind of fun faux-pretentious humor to call it Dobsonian in the manner of the Newtonian, but simultaneously also a true nod of respect to John Dobson.

 

That said, I wasn’t "there"; I was just a kid viewing the bright stuff on and off with my EQ-mounted Newtonian on my own from my backyard and reading about the "Dobsonian" in magazines. Probably no one specifically said it was humor, but it just seemed like it was fun to say it that way. I mean, I couldn’t really understand what the big deal even was — I had never seen one for myself let alone used one, so definitely don’t take my impression as anything definitive.

 

Later it became a product category and the "put a smile on your face from just saying it" aspect was gone



#21 tommm

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Posted 17 February 2024 - 12:29 PM

I think it is one of those "everybody knows" if you say Dobsonian you mean a Newtonian reflector on a Dobsonian mount because that is what John Dobson made - as Keith said. But, a real Dobsonian mount is one made very cheaply out of readily sourced materials. That is what John did, showed how the "average man" could afford to have a large aperture telescope by making it himself out of common, low cost materials. No steel or aluminum mirror cells in them. No Zambuto mirrors.  Most of us now make Alt-Az mounts that John likely would have seen as unnecessarily costly. And he didn't have Ebony Star, Dave Kreige introduced that after testing various materials. The OR guys call their group the Alt-Az working group, not the Dobsonian working group.



#22 Eddgie

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Posted 17 February 2024 - 01:15 PM

To be a Dobsonian telescope, it must be made to the general design philosophy as was originated by John Dobson.  It consists of Newtonian telescope with a trunnion or modified trunnion style mount attached to a base that moves in azimuth. Nothing else is a Dobsonian. 

 

That is my story, and I am sticking to it. 


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#23 TOMDEY

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Posted 17 February 2024 - 01:32 PM

Ladies and Gentlemen --- I dare say the reason we aptly call them Dobsonians is because it references scopes derived from John Dobson's early constructs which comprised relatively large Newtonian optical configuration with nice compact sturdy minimalist wood Alt/Az mount. Simple as that, and simultaneously recognizes John's dedicated and profoundly generous engagement in our hobby. Nothing whatsoever nefarious in that. Get over the gnashing of teeth and celebrate both Isaac and John for their contributions.    Tom


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#24 rjacks

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Posted 17 February 2024 - 05:13 PM

I don't think Isaac Newton feels disrespected. His legacy is secure.


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#25 TOMDEY

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Posted 17 February 2024 - 05:36 PM

I don't think Isaac Newton feels disrespected. His legacy is secure.

Yeah... gratuitous surrogate outrage is kinda... ~White Night Syndrome~    Tom

 

What is White Knight Syndrome?

 

"Plenty of people fantasize about being saved by a knight in shining armor, but some of us fantasize about being that knight. There’s a term for that: White Knight Syndrome. It’s also sometimes called a “savior complex” or “rescue complex,” and it might sound familiar if you’ve ever found yourself going to great lengths to help other people. We’ll fill you in on what White Knight Syndrome is, exactly, and the different types and causes of it. We’ll also offer signs that you may be a white knight, yourself, and also how to take that shining armor off, for your own sake."  ~

 

Example: My wife (79) and I (76) were happily loading groceries into our trunk and a well-meaning 40-ish lady came up with a big smile on her face and offered, "Here - let me load that for you!" I said, "Thanks! - But our doctor encourages us to stay active for our health." Lady persisted, "But I'm a caring person; Here - let me help!" --- and continued to grab our groceries and accomplish her Quixotic deed, regardless. She finally left, commenting yet again, "I'm a caring person." Well meaning and --- creepy!

 

I agree that Sir Isaac most certainly doesn't need our help in defending his legacy.    Tom

Attached Thumbnails

  • 206.1 Isaac Newton John Dobson Bernhard Schmidt.jpg

Edited by TOMDEY, 17 February 2024 - 05:39 PM.

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