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Equipment Discussions >> Reflectors

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chaoscosmos
sage
*****

Reged: 01/26/13

Loc: Mission Viejo CA
Coulter Dobsonians
      #5644881 - 01/26/13 06:38 PM

Hey everyone, Greetings. I'm brand new here, just registered..

20+ years ago, I had a few experiences looking through the 10 and 13.1 inch Coulter Odyssey Dobsonians. The only telescope I ever owned was a small refractor, but now I'm looking to get something like a used Coulter or maybe a 12.5 inch Discovery Dob. I'm wondering how the two scopes compare- both optically and in general workmanship and ease of operation.

Also, does anyone know when Coulter went out of business or who they may have sold the company to?

Thanks...


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chaoscosmos
sage
*****

Reged: 01/26/13

Loc: Mission Viejo CA
Re: Coulter Dobsonians new [Re: chaoscosmos]
      #5644894 - 01/26/13 06:44 PM

.... just to be clear, the comparison I'm interested in is between Coulter and Discovery scopes... Aside from differences in aperture.

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Jim Rosenstock
Postmaster
*****

Reged: 07/14/05

Loc: MD, south of the DC Nebula
Re: Coulter Dobsonians new [Re: chaoscosmos]
      #5644907 - 01/26/13 06:53 PM

They are in different leagues. Discovery, by a mile.

Not to fault Coulter, the original "light bucket" Dob available commercially. Coulter got a LOT of ancient starlight onto amateurs' retinas, for sure. But by comparison to the Discovery, they are heavy, crude, and optically a bit of a crapshoot. Classic? You bet...but the Discovery's gonna be a much more user-friendly instrument.

Cheers,

Jim


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chaoscosmos
sage
*****

Reged: 01/26/13

Loc: Mission Viejo CA
Re: Coulter Dobsonians new [Re: Jim Rosenstock]
      #5644949 - 01/26/13 07:19 PM

Thanks Jim.. OK then, how would Coulter compare to Orion's scopes? The Orion mount on their Dobs, just looking at photos of it, seems to be kind of cheesy.

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kfiscus
Carpal Tunnel
*****

Reged: 07/09/12

Loc: Albert Lea, MN, USA
Re: Coulter Dobsonians new [Re: chaoscosmos]
      #5645000 - 01/26/13 07:47 PM

I used to own an Odyssey Compact. I now own an Orion XT10 and Zhumell Z12. I highly recommend getting a Z12. A used scope looks to match your original post and intent. I have brokered or bought 3 different used/damaged-in-shipping Z12s that ran $360, $400, and $500. The most damaged tube's dent was SUPER easy to de-dent.
As to the cheesiness of the Orion spring tension mount (now that I have the Z12's friction bearings) they're not cheesy- they're annoying.


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tubehead999
scholastic sledgehammer
*****

Reged: 11/25/08

Loc: Kennesaw, GA
Re: Coulter Dobsonians new [Re: chaoscosmos]
      #5645004 - 01/26/13 07:49 PM

I don't know how they stay in business..but this is what is left of Coulter Optical.

http://www.e-scopes.cc/

Seriously, there are better options out there...
www.telescopes.com
www.opticsmart.com But they never have any scopes in stock because they sell them as fast as they get them in ..

And check your local Craigslist for used deals.

Best.


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Jon Isaacs
Postmaster
*****

Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Coulter Dobsonians new [Re: chaoscosmos]
      #5645037 - 01/26/13 08:03 PM Attachment (20 downloads)

Quote:

Thanks Jim.. OK then, how would Coulter compare to Orion's scopes? The Orion mount on their Dobs, just looking at photos of it, seems to be kind of cheesy.




First let me say hello and welcome to Cloudy Nights..

Second, there are two manufacturers of modern commercial Dobs, Synta Optical in China and Guan Sheng Optical (GSO) in Taiwan. Orion sells the Synta scopes, Skywatcher is the Synta house brand. Astro-Tech, Zhumell, Apertura and others sell the GSO scopes.

There are minor differences between them but both represent serious upgrades over the Coulter scopes. This is in every aspect, better optics, smoother bearings, lighter weight, better focusers (2 inch, 2 speed Crayfords are standard on the GSO dobs), better fit and finish...

The modern metal tube Dob hit the scene about the turn of the millennium... You get a lot of scope for your money..

My 10 inch GSO is about 10 years old, still going strong.

Jon


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Bob W6PU
Carpal Tunnel
*****

Reged: 12/23/04

Loc: Springer-N.E.NM
Re: Coulter Dobsonians new [Re: Jim Rosenstock]
      #5645068 - 01/26/13 08:21 PM

Ditto, all the way!

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GeneT
Ely Kid
*****

Reged: 11/07/08

Loc: South Texas
Re: Coulter Dobsonians new [Re: chaoscosmos]
      #5645085 - 01/26/13 08:31 PM

I owned a 13.1 inch 'blue' tube Coulter. It was my first large telescope, and quite inexpensive. However, the optics were poor, and it was very difficult to collimate. I do not recommend this telescope.

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JIMZ7
Pooh-Bah
*****

Reged: 10/22/05

Loc: S.E.Michigan near DTW
Re: Coulter Dobsonians new [Re: chaoscosmos]
      #5645148 - 01/26/13 09:16 PM

Welcome to CN! You might want to check into your local astronomy club for used telescopes etc. There are some great deals out there.

Jim


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faackanders2
Carpal Tunnel


Reged: 03/28/11

Re: Coulter Dobsonians new [Re: chaoscosmos]
      #5645153 - 01/26/13 09:23 PM

my first teleescope was a 10.1" Coulter Dob which I used for over 15 years. Breaks down into 2 nested parts and fit in my Mustang. Didn't need to colimate single tube for 10 years. 5 min setup time and easy to move anywhere. It was simple and used 2" outer pipe fitting and a 1.25" inner sliding pipe as a focuser. i did buy my 40mm 70afov eyepiece hoping I coul use it but there is a big difference betwen 2" ID an OD so I could only briefly holed it in place till i installed a 2" focuser. Bought 2 but installed neither.

2nd telescope and only one used now for night is 17.5" f4.1 split tube Discovery. Breaks down into 3 parts, 2 of which nest. Fits in my Expedition/Navigator (and would also fit in Explorer and other SUVs). Heaviest part is bottom half mirror cell with handles but weiht 98 lbs, and the most dificult/risky part is transitioning from vertical to horizontal at the rear of my SUV (not tall enough to tip over inside the SUV). Major advantage of the Discovery was it had a real 2" focuser (Note in a few years 3" focuser may become optional in large dobs offering wider views).
15-20min Easy to set up and take down, but requires columation due to the split tube. Later had wheel barrel handles made to be able to move around (before the wheel barel handles where I set up was where I viewed). With wheel barel handles easy to roll in/out of garage to view, so I don't have to pack my car and travel to site everytime.
Wait time for Discovery is long.

Recommend get largest dob you can transport and carry. Truss tubes make individual pieces smaller and lighter but take longer to set up. Many like Light bridge truss dobs, and Discovery has them also.

Orion, Zhumel, Hardin all make simple Dobs. Best value for aperture. Non push to requires you knowing where to look (shar charts/bookk, viewing with those who know sky objects. Push or Go-To cost more but after alligning and set up you just need to know what us and type in object and push to with arrow directions to the object.

You get what you pay for. Simple dons can be found used at swap events. Join a club and you will probably find someone who wants to upgrade. It is also nice to observe with others to see what is out there, before you buy.

Good luck!


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chaoscosmos
sage
*****

Reged: 01/26/13

Loc: Mission Viejo CA
Re: Coulter Dobsonians new [Re: JIMZ7]
      #5645160 - 01/26/13 09:33 PM

Good info guys, much appreciated...

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chaoscosmos
sage
*****

Reged: 01/26/13

Loc: Mission Viejo CA
Re: Coulter Dobsonians new [Re: chaoscosmos]
      #5645174 - 01/26/13 09:42 PM

Btw I've got a Camry to transport, but a lot of the time I'd probably view from my backyard. Since I live in Orange County Ca there is some light pollution, but my yard is somewhat protected. It sits in sort of a bowl, bordered by a slope in the back, side fences, and back wall of the house.

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Tom Andrews
Pooh-Bah
*****

Reged: 01/25/07

Loc: Albuquerque, NM
Re: Coulter Dobsonians new [Re: chaoscosmos]
      #5645238 - 01/26/13 10:45 PM Attachment (45 downloads)

Ditto for everything everyone has said.

I bought my first scope in 1995, an 8" Coulter and I still have it. I have modified it considerably and it is a joy to use. BUT the only reasons I have kept it is because it was my first scope and all the work I've put into it. Today's scopes offer so much more and for very reasonable prices. I've owned an 8" Zhumell and a 12.5" Discovery PDHQ split-tube dob and they were both head-and-shoulders above the Coulter.

For nostalgia purposes, here's a picture of my Coulter:


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chaoscosmos
sage
*****

Reged: 01/26/13

Loc: Mission Viejo CA
Re: Coulter Dobsonians new [Re: Tom Andrews]
      #5645316 - 01/27/13 12:09 AM

Ah, now I remember that red color of the Odyssey. One thing though with regard to the newer scopes... Is a metal tube a bit colder to the touch at night?

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kfiscus
Carpal Tunnel
*****

Reged: 07/09/12

Loc: Albert Lea, MN, USA
Re: Coulter Dobsonians new [Re: chaoscosmos]
      #5645374 - 01/27/13 02:01 AM

Absolutely colder to the touch. I forgot to mention that my Coulter was the blue model with the r&p focuser.

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

Reged: 06/24/03

Loc: Los Angeles
Re: Coulter Dobsonians new [Re: chaoscosmos]
      #5645376 - 01/27/13 02:02 AM

OK, the Discovery has:
--better mirror cell
--better mirror
--better coatings
--better secondary mirror
--better secondary holder
--better focuser
--better bearings
--better wood construction in the base
--better wood
Did I leave anything out?
This is a little like comparing a Lada with a Lamborghini. It's just not, uh, a fair comparison.
From what I've seen over the years, even if the Coulter were FREE, you'd be in for a lot of modification just to get it to perform at a level about 50% of the Discovery.

Now, of course Orion, Apertura, Meade, and other inexpensive dobs are also better than the old Coulters, but by the time you get to 12-12.5", a truss tube is a lot easier to transport than a full tubed scope, and that reduces your options quite a bit.

I've known people who've bought an old Coulter and put the mirrors in a modern housing from DobStuff.com or AstroSystems, and gotten a really decent scope for cheap. But it would depend on how cheaply you got the old Coulter.


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Calypte
Pooh-Bah


Reged: 03/20/07

Loc: Anza, California
Re: Coulter Dobsonians new [Re: Starman1]
      #5645427 - 01/27/13 03:40 AM

Is it possible to collimate the secondary on the Coulter? Many years ago our club held a daytime public event, and someone brought a Coulter to have one of us "experts" evaluate it or explain how to use it or collimate it or something like that. It had the secondary mounted like the one in the earlier picture, where it's held on that steel bar across the aperture of the scope. I was absolutely stumped as to how to get the secondary properly aligned, since I saw only one adjustment.

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Howie Glatter
Vendor


Reged: 07/04/06

Re: Coulter Dobsonians new [Re: Calypte]
      #5645563 - 01/27/13 07:41 AM

>. . I saw only one adjustment.

There are two - loosen the two bolts on the ends of the bar(outside the tube) for tipping the secondary up and down.
Loosen the single bolt holding the secondary bracket at the center of the bar for side-to-side adjustment.

My first scope was from Coulter in 1990, a 10.1" red tube Oddessy Compact ($299), and for sentimental reasons I don't think I will ever part with it. The mirror is decent, although a bit rough. The original aluminum coating is still good. The only modifications I've done were moving the altitude bearings for better balance, and replacing the focuser with one made from a Leitz camera lens barrel with helical focus.
The fact that the tube fits across the back seat of a small automobile makes a 10.1" f/4.5 wonderfully portable.


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azure1961p
Postmaster
*****

Reged: 01/17/09

Loc: USA
Re: Coulter Dobsonians new [Re: Howie Glatter]
      #5645895 - 01/27/13 11:42 AM

Coulter had its place in time but its a relic with the baggage that's been outmoded by better designs and execution. Though some Coulter images were mighty fine. It had its place and if I had one and the optics were good I'd probably redo everything from the ground up.

Pete


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piaras
scholastic sledgehammer


Reged: 01/26/09

Loc: Niagara Region
Re: Coulter Dobsonians new [Re: azure1961p]
      #5645920 - 01/27/13 11:56 AM Attachment (22 downloads)

I have had a Coulter Odyssey 13.1 since 1990 about. There is not much left that is original any more. I built a truss setup around the optics and the only thing still original is the base, to be replaced this spring and the primary mirror, which is about 60 days away from replacement as well. Zambuto!
Pierre


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Kutno
Pooh-Bah
*****

Reged: 08/17/09

Re: Coulter Dobsonians new [Re: Calypte]
      #5646323 - 01/27/13 04:08 PM

Quote:

Is it possible to collimate the secondary on the Coulter?




A hammer worked splendidly. Only had to do it once; thereafter, the Odyssey Compact gave wonderful views of Saturn, Jupiter, and lunar landscapes.


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

Reged: 06/24/03

Loc: Los Angeles
Re: Coulter Dobsonians new [Re: Kutno]
      #5646568 - 01/27/13 06:05 PM

Quote:

Quote:

Is it possible to collimate the secondary on the Coulter?





A hammer worked splendidly. Only had to do it once; thereafter, the Odyssey Compact gave wonderful views of Saturn, Jupiter, and lunar landscapes.



The "bar" can be turned with a large crescent wrench. The secondary can be turned in the other axis with a plastic washer between the plate and bar and a box end wrench on the nut.
Not exactly fine tune adjustments, however.


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Kutno
Pooh-Bah
*****

Reged: 08/17/09

Re: Coulter Dobsonians new [Re: Starman1]
      #5646855 - 01/27/13 08:16 PM

Quote:

Quote:

Quote:

Is it possible to collimate the secondary on the Coulter?





A hammer worked splendidly. Only had to do it once; thereafter, the Odyssey Compact gave wonderful views of Saturn, Jupiter, and lunar landscapes.



The "bar" can be turned with a large crescent wrench. The secondary can be turned in the other axis with a plastic washer between the plate and bar and a box end wrench on the nut.
Not exactly fine tune adjustments, however.




I wish I had the option to use a wrench alone, Don. Things were so frozen that I had no choice. Only by the grace of God did everything fall into place so that the special Orion eyepiece I used showed the scope was perfectly collimated after the blow.


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

Reged: 06/24/03

Loc: Los Angeles
Re: Coulter Dobsonians new [Re: Kutno]
      #5646961 - 01/27/13 09:16 PM

Quote:

Quote:

Quote:

Quote:

Is it possible to collimate the secondary on the Coulter?





A hammer worked splendidly. Only had to do it once; thereafter, the Odyssey Compact gave wonderful views of Saturn, Jupiter, and lunar landscapes.



The "bar" can be turned with a large crescent wrench. The secondary can be turned in the other axis with a plastic washer between the plate and bar and a box end wrench on the nut.
Not exactly fine tune adjustments, however.




I wish I had the option to use a wrench alone, Don. Things were so frozen that I had no choice. Only by the grace of God did everything fall into place so that the special Orion eyepiece I used showed the scope was perfectly collimated after the blow.




Was that a Howie Glatter hammer or a Catseye hammer?


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Kutno
Pooh-Bah
*****

Reged: 08/17/09

Re: Coulter Dobsonians new [Re: Starman1]
      #5647128 - 01/27/13 10:54 PM

Quote:

Quote:

Quote:

Quote:

Quote:

Is it possible to collimate the secondary on the Coulter?





A hammer worked splendidly. Only had to do it once; thereafter, the Odyssey Compact gave wonderful views of Saturn, Jupiter, and lunar landscapes.



The "bar" can be turned with a large crescent wrench. The secondary can be turned in the other axis with a plastic washer between the plate and bar and a box end wrench on the nut.
Not exactly fine tune adjustments, however.




I wish I had the option to use a wrench alone, Don. Things were so frozen that I had no choice. Only by the grace of God did everything fall into place so that the special Orion eyepiece I used showed the scope was perfectly collimated after the blow.




Was that a Howie Glatter hammer or a Catseye hammer?




Now that would truly be innovative!

Sorry to disappoint you: It was a Stanley 20 oz. claw hammer with a wooden handle. The Compact is long gone; but the Stanley is still in my tool bag.


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markseibold
Carpal Tunnel


Reged: 01/19/08

Loc: Portland Oregon
Re: Coulter Dobsonians new [Re: Jon Isaacs]
      #6618162 - 07/05/14 02:43 PM

Quote:

Quote:

Thanks Jim.. OK then, how would Coulter compare to Orion's scopes? The Orion mount on their Dobs, just looking at photos of it, seems to be kind of cheesy.



First let me say hello and welcome to Cloudy Nights..

Second, there are two manufacturers of modern commercial Dobs, Synta Optical in China and Guan Sheng Optical (GSO) in Taiwan. Orion sells the Synta scopes, Skywatcher is the Synta house brand. Astro-Tech, Zhumell, Apertura and others sell the GSO scopes.

There are minor differences between them but both represent serious upgrades over the Coulter scopes. This is in every aspect, better optics, smoother bearings, lighter weight, better focusers (2 inch, 2 speed Crayfords are standard on the GSO dobs), better fit and finish...

The modern metal tube Dob hit the scene about the turn of the millennium... You get a lot of scope for your money..

My 10 inch GSO is about 10 years old, still going strong.

Jon




I agree with all of you and one did say that these old Coulter scopes got a lot of light photos onto new viewers retinas.

Just to throw in my few cents [literally], I ordered a 10.1 Coulter Dobsonian in 1987, believe this or not, you put $100 down and upon delivery almost a year later, you picked up the balance due of $139 + $47 in shipping, so who would complain about the Coulters then which a 10" Light bucket for $239 were showing us about every Dim Fuzzy and I can say this- I still use mine today- after 25 years I have never colimated or cleaned the primary mirror and it still performs like the day I received at the local truck shipping dock here in Portland, wrapped in a flimsy cardboard box and a few California Newspapers crumpled and thrown in the box to protect it . The Extra 6mm Orthoscopic Eyepiece I also ordered from Coulter is still one of my best eyepieces. That includes comparing it to later Meade and Celestron Super Plossls that i also purchased.

I know what better optics there are today, as I've seen them all and observed many times with them. I also more recently bought a Hardin Optical 10 inch Dob from Sean's Astronomy Shop in Battleground (Sean's business is now gone) for a mere $300 Wholesale, as I got a deal while working for Sean, to take the new Hardin to the Fiji Islands to observe with- A beautiful instrument and much improved over my old crude Coulter, but again, who would complain about great optics in an old antique truck frame like the Coulter at $239 or the Hardin, a new lightweight metal tube and silky smooth rack and pinion, with a 2 inch Eyepiece holder at $300?! Hardin even gave you a 2 inch 32mm Eyepiece! and two other medium to medium high magnification eyepieces! Also off topic, I also took John Dobson to lecture to local schools and we provided much sidewalk astronomy with the Hardin 10" scopes. Dobson endorsed both the quality of the old Coulter's and the newer Hardin's.

Yes, I have observed through the Discovery's scopes that Sean also had at the shop store, and they are very nice, as are the Zhummel, but hows your pocketbook? You did not really mention your budget. I have friends that have the Obsession 16 and 20 if you like professional observatory quality images. But the Obsessions are monsters, yet portable.

If you can find a give-away older Hardin, Coulter, or other older brands still in good shape on Craigs list, they are a steal, and good usable optics to still enjoy. I have made many detailed sketches of the moon through my old Coulter, and Spaceweather, APOD, etc have displayed these artworks on their front page as special featured.

Mark Seibold, retired IT, Artist-Astronomer, Portland Oregon
Mark Seibold Astro Sketch Gallery - 8 pages - please see all


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markseibold
Carpal Tunnel


Reged: 01/19/08

Loc: Portland Oregon
Re: Coulter Dobsonians new [Re: Kutno]
      #6618193 - 07/05/14 03:01 PM

Quote:

Quote:

Quote:

Quote:

Quote:

Quote:

Is it possible to collimate the secondary on the Coulter?





A hammer worked splendidly. Only had to do it once; thereafter, the Odyssey Compact gave wonderful views of Saturn, Jupiter, and lunar landscapes.



The "bar" can be turned with a large crescent wrench. The secondary can be turned in the other axis with a plastic washer between the plate and bar and a box end wrench on the nut.
Not exactly fine tune adjustments, however.




I wish I had the option to use a wrench alone, Don. Things were so frozen that I had no choice. Only by the grace of God did everything fall into place so that the special Orion eyepiece I used showed the scope was perfectly collimated after the blow.




Was that a Howie Glatter hammer or a Catseye hammer?




Now that would truly be innovative!

Sorry to disappoint you: It was a Stanley 20 oz. claw hammer with a wooden handle. The Compact is long gone; but the Stanley is still in my tool bag.




Here's how Dobson employs his expert method of collimation... > He is shown doing it here at 5:25 mins on the time bar >
https://www.youtube.com/watch?v=J_slAX3hzCo

-Mark Seibold


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DoctorNoodle
Pooh-Bah
*****

Reged: 07/14/07

Loc: Lawn Guyland, NY
Re: Coulter Dobsonians new [Re: markseibold]
      #6618291 - 07/05/14 04:01 PM

Just to throw in my 2 cents, I owned a blue-tube Odyssey 10.1 inch for 20 years and replaced it with an Orion 8-inch f/4.9. I used to love that big blue monster and thought it was the best scope I've ever looked through.

Now that I've had the Orion for several months, I realize I was wrong. I'm actually able to see more in the 8-inch Orion than in the 10.1-inch Odyssey. I can see more detail in DSOs under the same observing conditions. I'm also able to see more DSOs. The Odyssey was useless on planets unless it was stopped down to 3.5 inches which darkened the image. I can see some nice planetary detail in the 8-incher.

Don't get me wrong, I still miss that big blue heap o' flakeboard and cardboard.


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droid
rocketman
*****

Reged: 08/29/04

Loc: Conneaut, Ohio
Re: Coulter Dobsonians new [Re: markseibold]
      #6619207 - 07/06/14 08:05 AM

Here's how Dobson employs his expert method of collimation... > He is shown doing it here at 5:25 mins on the time bar >
https://www.youtube.com/watch?v=J_slAX3hzCo

-Mark Seibold




I remember that, I kept thinking, man Im collimating all wrong, lol......I really wish I could find the whole episode.


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kfrederick
Carpal Tunnel
*****

Reged: 02/01/08

Re: Coulter Dobsonians new [Re: droid]
      #6619348 - 07/06/14 10:08 AM

My first telescope was a Coulter 13 inch it was so heavy and was not perfect but it was a fun telescope .I sold it 15 years later and got all I spent on it .When it was new. So 15 years of fun for free . I do think the new ones are better . But I not throw one away, just the structure . It not take much to re figure the primary much less than making one from scratch .

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17.5Dob
sage


Reged: 03/21/13

Loc: Colorado,USA
Re: Coulter Dobsonians new [Re: Jim Rosenstock]
      #6620333 - 07/06/14 07:33 PM

Quote:



Not to fault Coulter, the original "light bucket" Dob available commercially. Coulter got a LOT of ancient starlight onto amateurs' retinas, for sure.

Cheers,

Jim





I went the ATM route, and back in 1982, I ordered just the primary/ secondary pair for the 17.5", for all of $659.00. I'm a trim carpenter so the base,cell,rocker and tube was all free, using scrap from work.

I bought my spider and focuser from Novak, built my own finder from salvaged parts from a 7 X 50 binocular, and bought 2, Teleview Plossls, for a grand total of just under $1,000.00.

That "ancient" mirror pumped MANY photons through my eyes as well as many others. Being the largest amateur scope in the area for many years, I was constantly hauling it to Star Parties, hosting open house backyard observing sessions,etc..

It wasn't 1/10 wave for sure, but wasn't at all bad either. It just took a bit of collimation, every single time out, to get it tweaked just right. Most nights were always seeing limited, and were spent observing DSO's, it's forte, but on those rare occasions when it was really steady, it did an awesome job on fine planetary details.

"Back in the Day", it was an unbeatable bargain !


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Philler
sage


Reged: 07/15/13

Loc: Kansas, USA
Re: Coulter Dobsonians new [Re: 17.5Dob]
      #6620661 - 07/06/14 11:07 PM

I still own and use the 10.1" Coulter red. I will eventually either upgrade it or maybe buy like a Meade 12" strut model Lightbridge.

The tricks I have learned with collimating the 10" Coulter primary with the as provided cell with the 3 adjustment screws and the 3 "lock" (washered) screws, is to elevate the scope resting on like 3 small stools to sit up high enough. I use these 3 collapsable stools from Home Depot that can be transported and are each rated at 300 lbs. For the secondary strut, I loosen the side bolts for vertical adjustment and then the center bolt behind the secondary mirror for the side to side adjustment and only enough so they are just snug enough to control the adjustment and center the secondary in the focuser tweaking the bolts using a cheshire, sighting tube, or whatever you like to use. Instead of using wrenches to retighten the secondary bolts, I have found that using my fingers to re-tighten them snuggly is enough--and they have held their adjustment and I have not had to re-adjust them recently. If you try to use a wrench to re tighten them it will probably throw your fine adjustment off. As for adjusting the primary, point the scope vertically, loosen the 3 lock screws (the ones with washers) a couple of turns. Using whatever technique and cheshire or lazer collimator you prefer, you can then turn the rear adjustment screws with your fingers to align the center spot correctly. I have never had to use a screw driver to turn the adjustment screws. When everything looks aligned properly go back a re tighten the "lock screws." But here you can go wrong an mess up your primary alignment. Only use your fingers and a small stubby screw driver and snug the lock screws just enough until they just feel snug. Don't worry about the washers being snug, they don't have to be snug; all you are trying to do is stabilize the main mirror by taking up any slack from the differences in the adjustment screws, so it will stay aligned to and at your observing session.
Using this method I have had to do very little or even no re collimation between observing trips to my DSS. And, as I have said, the secondary has stayed adjusted since I reinstalled it and the primary last December after I got them back from being recoated.

Please note: the above is not a tutorial on all the details of collimation; but is simply some tricks I have learned on how to deal with the as-shipped red Coulter 10.1 " scope with its primary cell and secondary strut, and what has worked well for my collimating it. And using the three small folding stools is an aid for collimation in the field.
If you have one of these scopes certainly improvements can be done: removing the primary mirror and cutting cooling holes in the existing cell, and even rigging up a cooling fan for the rear cell, standard veined spiders are available to replace the strut. Replacing the primary cell can be done , but can introduce some new problems like mirror location and balance issues. Also, if you are really concerned about the quality of your Coulter mirror, I think I read that Novak, Owl, or one of these optical companies that re-coat mirrors will test your primary and can even re-figure it if you wish.

Edited by Philler (07/07/14 10:03 AM)


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Philler
sage


Reged: 07/15/13

Loc: Kansas, USA
Re: Coulter Dobsonians new [Re: Starman1]
      #6621007 - 07/07/14 08:28 AM

Quote:

Quote:

Quote:

Is it possible to collimate the secondary on the Coulter?





A hammer worked splendidly. Only had to do it once; thereafter, the Odyssey Compact gave wonderful views of Saturn, Jupiter, and lunar landscapes.



The "bar" can be turned with a large crescent wrench. The secondary can be turned in the other axis with a plastic washer between the plate and bar and a box end wrench on the nut.
Not exactly fine tune adjustments, however.




My 10" Coulter compact had sat idle covered in my shed until I decided to get the mirrors recoated last fall. I found that the middle bolt holding the secondary to the strut was stuck and wouldn't budge no matter how much wrench torque I applied. I took the strut outdoors on the deck and carefully sprayed the bolt with Liquid Wrench. After a few hours I was able to turn the bolt to remove the secondary. Happy ending, no hammer needed.

Edited by Philler (07/07/14 08:30 AM)


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Philler
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Reged: 07/15/13

Loc: Kansas, USA
Re: Coulter Dobsonians new [Re: Howie Glatter]
      #6621082 - 07/07/14 09:46 AM

Quote:

>. . I saw only one adjustment.

There are two - loosen the two bolts on the ends of the bar(outside the tube) for tipping the secondary up and down.
Loosen the single bolt holding the secondary bracket at the center of the bar for side-to-side adjustment.

My first scope was from Coulter in 1990, a 10.1" red tube Oddessy Compact ($299), and for sentimental reasons I don't think I will ever part with it. The mirror is decent, although a bit rough. The original aluminum coating is still good. The only modifications I've done were moving the altitude bearings for better balance, and replacing the focuser with one made from a Leitz camera lens barrel with helical focus.
The fact that the tube fits across the back seat of a small automobile makes a 10.1" f/4.5 wonderfully portable.




I have what you have; a 10.1" f/4.5 Coulter Compact red. I ordered it in 1992 and received it months later.
I agree with you, the optics on mine are decent, but not top of the line. I continue to be amazed at the detail in deep sky objects I am seeing with it. And I disagree with the Coulter critics who are saying these scopes are inferior.
I too use the back seat method of transporting my 10". I will strap it to a two wheeler and transport it to my 4 door Focus and carefully place it cross ways in the back seat. And then, as a precaution, use the 2 nylon adjustable moving straps to wrap around both front part and back part of the tube and tightened around each of the two rear seat head restraints. This acts like 2 seat belts for the scope traveling to my observing site.
I, too, replaced the original pipe and PVC focuser with a Lumicon helical focuser. This kind of focuser works well and is precise, and is especially nice if you use parfocal eyepieces.

Edited by Philler (07/09/14 01:54 PM)


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