Jump to content


Photo

Coulter Optics

  • Please log in to reply
54 replies to this topic

#1 TCW

TCW

    Surveyor 1

  • *****
  • Posts: 1862
  • Joined: 05 Nov 2013
  • Loc: Somewhere in a galaxy far, far away.

Posted 25 July 2014 - 02:14 PM

I see Coulter scopes for sale all the time on CL but rarely see any posts on CN discussing these telescopes.

I have been searching the internet for information on Coulter - history, telescopes, reviews and users but have not found much.

I also wonder how many of the 29" monsters were made and if any survive.

#2 magic612

magic612

    Soyuz

  • *****
  • Posts: 3777
  • Joined: 30 Sep 2008

Posted 25 July 2014 - 02:37 PM

I bought one of the older blue tube 10" f4.3 Coulter reflectors for about $50 or $75 (can't remember) several years ago. Despite the coatings peeling off the primary and a challenging secondary collimation process, it produced a pretty darn decent image and star test. As I understand it, the Coulters were hit and miss though - some were surprisingly decent (not great, but decent), and others were... well, not all that great.

Don't know about the 29" ones, but I have seen a couple 17" ones pop up somewhat infrequently.

#3 TCW

TCW

    Surveyor 1

  • *****
  • Posts: 1862
  • Joined: 05 Nov 2013
  • Loc: Somewhere in a galaxy far, far away.

Posted 25 July 2014 - 02:42 PM

I ran a wanted ad for telescopes in a local forum and got a call from a guy who said he had a 13" Coulter. I went to look at it and when I got there he told me it had been sitting out in the rain for years and that he lost the mirror!

There is a 17.5" for sale on CL that I find somewhat intriguing and it might be cheap way to get into a big Dob.

That secondary support would be the first thing to go if I get one of these scopes.

#4 rcwolpert

rcwolpert

    Viking 1

  • *****
  • Posts: 827
  • Joined: 13 Aug 2012
  • Loc: San Jose, CA

Posted 25 July 2014 - 03:05 PM

Back in 1981 I purchased a full-thickness, specially selected, 12.5", f/6.3 mirror from Coulter, and I made a Dobsonian, which later became a Newtonian. I brought it to Stellafane in 1981 and had long lines at the scope to get a view. That mirror and it's diagonal were amazingly good. I wish I kept that mirror. Sold it around 1999.

- Bob

#5 wfj

wfj

    Apollo

  • *****
  • Posts: 1184
  • Joined: 10 Jan 2008
  • Loc: California, Santa Cruz County

Posted 25 July 2014 - 03:33 PM

http://www.cloudynig...3408498/page...

#6 Geo31

Geo31

    Vanguard

  • *****
  • Posts: 2182
  • Joined: 28 Jan 2013
  • Loc: Kingwood, TX

Posted 25 July 2014 - 04:37 PM

Um....

Dobsonians ARE Newtonians. :)

#7 rcwolpert

rcwolpert

    Viking 1

  • *****
  • Posts: 827
  • Joined: 13 Aug 2012
  • Loc: San Jose, CA

Posted 25 July 2014 - 07:46 PM

Um....

Dobsonians ARE Newtonians. :)

Not really.
When I turned it into a Newtonian, I was on a 1/2 ton equatorial mount. That's nothing like John Dobson imagined of doing. I think S&T recently had an article or letter on the difference between a Dobsonian and a Newtonian. It's a common error.

- Bob

#8 photiost

photiost

    Viking 1

  • *****
  • Posts: 887
  • Joined: 14 Dec 2006
  • Loc: Montreal, Canada

Posted 25 July 2014 - 07:54 PM

I think a Newtonian telescope does not change regardless of how it is mounted.

#9 rcwolpert

rcwolpert

    Viking 1

  • *****
  • Posts: 827
  • Joined: 13 Aug 2012
  • Loc: San Jose, CA

Posted 25 July 2014 - 07:57 PM

To put it another way, every Dobsonian has a Newtonian optical path, but not every Newtonian is a "Dobsonian".

- Bob

#10 Bomber Bob

Bomber Bob

    Vanguard

  • *****
  • Posts: 2287
  • Joined: 09 Jul 2013
  • Loc: The Deep South, USA

Posted 25 July 2014 - 08:17 PM

The 8" that I built was neither a Dobsonian nor a Newtonian, it was - bless it! - a JayDubian...

(... and no, I didn't bother patenting it!)

#11 tim53

tim53

    Cosmos

  • *****
  • Posts: 9259
  • Joined: 17 Dec 2004
  • Loc: Highland Park, CA

Posted 25 July 2014 - 08:25 PM

To put it another way, every Dobsonian has a Newtonian optical path, but not every Newtonian is a "Dobsonian".


Thank God for that! :grin:

#12 Geo31

Geo31

    Vanguard

  • *****
  • Posts: 2182
  • Joined: 28 Jan 2013
  • Loc: Kingwood, TX

Posted 25 July 2014 - 08:35 PM

To put it another way, every Dobsonian has a Newtonian optical path, but not every Newtonian is a "Dobsonian".

- Bob


Uh, yeah. But pretty much every Dobsonian IS a Newtonian, which is exactly what I said. A Newtonian is defined by the optical path.

#13 rcwolpert

rcwolpert

    Viking 1

  • *****
  • Posts: 827
  • Joined: 13 Aug 2012
  • Loc: San Jose, CA

Posted 25 July 2014 - 08:38 PM

Anyway, I had a great Coulter mirror!! ;)

#14 Geo31

Geo31

    Vanguard

  • *****
  • Posts: 2182
  • Joined: 28 Jan 2013
  • Loc: Kingwood, TX

Posted 25 July 2014 - 08:41 PM

Um....

Dobsonians ARE Newtonians. :)

Not really.
When I turned it into a Newtonian, I was on a 1/2 ton equatorial mount. That's nothing like John Dobson imagined of doing. I think S&T recently had an article or letter on the difference between a Dobsonian and a Newtonian. It's a common error.

- Bob


Not really? Seriously?

A Dobsonian is more or less defined by the mount. A Newtonian is defined by the optical path.

All Dobs are Newts while not all Newts are Dobs. Just like all Squares are Rectangles while not all Rectangles are Squares.

Pretty simple. I don't know what S&T wrote.

#15 k5apl

k5apl

    Viking 1

  • *****
  • Posts: 808
  • Joined: 19 May 2006
  • Loc: Arkansas

Posted 25 July 2014 - 08:47 PM

Back in the day I owned a 10 inch Coulter. It had poor images and a blue tube. I sold it.
Then I bought a blue tube 13 inch Coulter Dob. It had excellent images. I had a nice plywood box to keep the mirror in when not in use. I eventually sold it. Think I was
one of the buyers that actually got really good optics. Some
say blue tube scopes were better than red tube scopes. Just
the luck of the draw, I guess.
Wes

#16 rcwolpert

rcwolpert

    Viking 1

  • *****
  • Posts: 827
  • Joined: 13 Aug 2012
  • Loc: San Jose, CA

Posted 25 July 2014 - 08:53 PM

George, I think we are saying the same thing. At Stellafane I had a Dobsonian. When I mounted it in my observatory, I had a Newtonian. Here's what Optec says, "Newtonians and their variant, the Dobsonian, are types of reflecting telescopes. Using a simple concave primary mirror design with a flat secondary, Newtonian designs have the advantage of being inexpensive to produce, but they also provide a crisp view. These simple designs are highly popular among amateur astronomers worldwide. If you want a lot of bang for your buck, a Newtonian or a Dobsonian may be just what you are looking for!

What is the difference between a Newtonian and a Dobsonian? A Newtonian is an optical design, and a Dobsonian is a mount style. Normally, a Dobsonian is a Newtonian, but a Newtonian is not always a Dobsonian! You can buy a Newtonian style telescope on any mount: equatorial, alt-azimuth, and even Dobsonian. Feel free to check them out because you will always get a lot of aperture for the money with the versatile and budget-friendly Newtonian."

So, we really agree!

- Bob

#17 actionhac

actionhac

    Skylab

  • *****
  • Posts: 4268
  • Joined: 09 Aug 2008
  • Loc: Seattle

Posted 25 July 2014 - 09:30 PM

I've enjoyed the Coulters immensely.
The blue tube 17.5 inch was spectacular.
Two red tube Odyssey 8's, a 10" blue tube, a brown Odyssey 8, a excellent 6"f8 mirror and 10"f5.6 mirror, all fantastic.

Robert

#18 Chuck Hards

Chuck Hards

    Fly Me to the Moon

  • *****
  • Moderators
  • Posts: 5462
  • Joined: 03 May 2010
  • Loc: The Great Basin

Posted 25 July 2014 - 09:51 PM

"Dobsonain" refers to a lot of things, but mainly, a minimalist approach to construction, using common materials, mounted on an alt-az base with simple kinematics that employ direct transfer of weight to low-friction sliding bearings.

The optical configuration is a secondary aspect, but Dobson favored the simplicity of the Newtonian and that's what most people think of when they hear "Dobsonian".

As to Coulter mirrors, I purchased many over the years. To this day, I still own a 17.5" f/4.5, a 10" f/5.6 full-thickness, and an 8" f/7 full-thickness. All are superb. The 17.5" has an ever-so-slight central hill, that is completely masked by the secondary shadow. The 8" dates to the mid-seventies, the 10" to the late seventies, and the 17.5" was purchased in 1986. I am the original owner of those 3.

I bought a half dozen 10" f/5.6 mirrors from them in the late 80s up to about 1991 or so, for the fiberglass Dobs I was making and selling. By then, they were no longer full-thickness (6:1 D to T ratio), but had thinned to 1" thick. After three of those that were acceptable (~1/4 wave), I switched to Intermountain Optics and bought some 10" mirrors from Vaughn Parsons that were much better optically and a full 2" thick!

I would rate the older Coulter mirrors a notch above later production. That's not to say that some of the later mirrors weren't excellent, but it seems the odds of a lemon sneaking-through more often were greater as the company approached it's final years.

#19 Geo31

Geo31

    Vanguard

  • *****
  • Posts: 2182
  • Joined: 28 Jan 2013
  • Loc: Kingwood, TX

Posted 25 July 2014 - 10:03 PM

George, I think we are saying the same thing. At Stellafane I had a Dobsonian. When I mounted it in my observatory, I had a Newtonian. Here's what Optec says, "Newtonians and their variant, the Dobsonian, are types of reflecting telescopes. Using a simple concave primary mirror design with a flat secondary, Newtonian designs have the advantage of being inexpensive to produce, but they also provide a crisp view. These simple designs are highly popular among amateur astronomers worldwide. If you want a lot of bang for your buck, a Newtonian or a Dobsonian may be just what you are looking for!

What is the difference between a Newtonian and a Dobsonian? A Newtonian is an optical design, and a Dobsonian is a mount style. Normally, a Dobsonian is a Newtonian, but a Newtonian is not always a Dobsonian! You can buy a Newtonian style telescope on any mount: equatorial, alt-azimuth, and even Dobsonian. Feel free to check them out because you will always get a lot of aperture for the money with the versatile and budget-friendly Newtonian."

So, we really agree!

- Bob


Yes and no I guess. At Stellafane your Dob was still a Newt.

I don't think Dobson ever produced a scope that was not a Newt (but I was out of this for a while, so I certainly could be wrong about this), so I would argue that you really shouldn't classify any scope as Dob if it's not a Newt.

#20 bremms

bremms

    Mercury-Atlas

  • *****
  • Posts: 2589
  • Joined: 31 Aug 2012
  • Loc: SC

Posted 25 July 2014 - 10:20 PM

A Newt is a type of Salamander.. But not all salamanders are newts.
I currently have a 10" F5.6 Coulter with a 1.375 mirror.
it looked decent at first glance on the stand.
Years ago a friend had a 10.1 and it had a good mirror. He picked up a 13.1 and it was bad. The 10.1 was so much better. We were going around to schools during comet Halley.

#21 rcwolpert

rcwolpert

    Viking 1

  • *****
  • Posts: 827
  • Joined: 13 Aug 2012
  • Loc: San Jose, CA

Posted 25 July 2014 - 10:47 PM

Okay, forgetting reference to names, at Stellafane that beautiful Coulter mirror was in an OTA that went through a big plywood box that moved smoothly on Teflon. At home that OTA was on a 1000 lb mount that moved smoothly with an 11" Mathis gear and drive system. In both configurations that Coulter mirror was superb! That's the scope I viewed Pluto with.

- Bob

#22 SpaceConqueror3

SpaceConqueror3

    Vostok 1

  • -----
  • Posts: 182
  • Joined: 19 Sep 2013
  • Loc: Phinney Ridge, Seattle, WA

Posted 05 August 2014 - 09:16 AM

I just got a Brown 8" Odyssey off craiglsit for my daughter. I haven't tried it at night yet but I'm glad to hear it's highly regarded by others here. It came with 6mm, 12mm Coulter Orthos and 27mm binocular/spotting scope looking eyepiece. I pop them into my PST and I liked the 12mm but the other two, not so much. Does anyone have these eyepiece? If so, what do you think of them?



#23 actionhac

actionhac

    Skylab

  • *****
  • Posts: 4268
  • Joined: 09 Aug 2008
  • Loc: Seattle

Posted 05 August 2014 - 09:51 AM

The brown tubes aren't seen very often, I'm still trying to figure out where they fit it the Odyssey models. Between the blue tube and the red tube, I think.

The Binocular eyepiece is the original equipment supplied with your telescope.

6mm and 12mm ortho's are probably very good eyepieces. The 6mm will  be much better at night.

 

Robert



#24 SpaceConqueror3

SpaceConqueror3

    Vostok 1

  • -----
  • Posts: 182
  • Joined: 19 Sep 2013
  • Loc: Phinney Ridge, Seattle, WA

Posted 05 August 2014 - 09:59 AM

I found this online about the Odyssey 8....

 

https://sites.google...erodyssey/index



#25 kt4hx

kt4hx

    Mariner 2

  • *****
  • Posts: 224
  • Joined: 21 Jan 2009
  • Loc: Fredericksburg, Va

Posted 05 August 2014 - 04:31 PM

I bought one of the big blue Odyssey II 17.5 inch monsters around 1980 (the one with the big rectangular mirror box.  It was a good performer, and gave me my first view of M51's spiral structure.  Eventually it was put into storage as other facets of life took priority.  Then a few years back, I had the optics redone, a truss structure built for them, and the massive structure went away.  I have a history with the mirrors, and plan to keep them going until I can't go any longer!

 

Here is some more documentation for Coulter I ran across:

 

http://geogdata.csun...ter/coulter.pdf

http://geogdata.csun...ter/CT-100.pdf








Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics