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Coulter Odyssey 8 focal ratio?

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#1 lightspeed66

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Posted 12 June 2016 - 08:35 PM

I've scored an Odyssey 8 and I know these were produced as an 4.5 and as an f7. Without any markings, how can I tell what it is? Is the focal length determined by the grind of the mirror? Thanks!

 

gallery_258703_6178_1529023.jpeg


Edited by lightspeed66, 12 June 2016 - 08:36 PM.

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#2 smeyer8015

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Posted 12 June 2016 - 08:38 PM

Measure the length of the tube If it's around 40" long, you have a F4.5. If it's closer to 60" you have an F7.

 

Scott



#3 J A VOLK

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Posted 12 June 2016 - 08:42 PM

The tube length is approximately mirror diameter x f#, thus obvious in your case (approx. 36" vs. 56")

#4 lightspeed66

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Posted 12 June 2016 - 09:12 PM

Thanks friends. It's 37" long so a f4.5 which is what I expected. Here's an iPhone / eyepiece snap of the moon just 5 minutes ago. 

 

gallery_258703_6178_110953.jpeg


Edited by lightspeed66, 12 June 2016 - 09:18 PM.

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#5 Bomber Bob

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Posted 12 June 2016 - 09:57 PM

I'd say the mirror cleaned up well - nice!

 

I know nothing about Coulter scopes - only saw a couple when I was in the Memphis club - don't recall ever looking through one.



#6 smeyer8015

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Posted 12 June 2016 - 09:59 PM

Seems like it works well...

 

 

Scott



#7 Tenacious

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Posted 12 June 2016 - 10:26 PM

Nice image.  I'll bet it delivers a pleasing view of DSOs.

 

I found an Odyssey advertisement in the November 1991 issue of S&T.  Sadly, there were no specifications listed, neither focal length nor ratio.  Instead, there were 2 testimonials.   :undecided:   "...it's worth twice what I paid, but don't raise your prices..."

 

Focal length - bring an EP to focus on some celestial target, measure from the focuser ring to the secondary, measure from the secondary back to the primary.  The sum of these should get you reasonably close.



#8 stevew

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Posted 12 June 2016 - 11:05 PM

The Odyssey 8 is a fun little scope.

I bought one about a 12 years ago for my kids. The mirror in mine needs to be re-done, so it has never been good on the planets, but that has not stopped my kids from learning the sky with it, and having hundreds of hours of pleasure using it on Messier objects..

Coulter's were never known for top flight mirrors, but I love the ruggedness of the thick Sonotube.

We put in a decent 2 inch helical focuser and last Summer we made a taller rocker box, as my kids are now taller than me..

 

Steve


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#9 lightspeed66

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Posted 12 June 2016 - 11:31 PM

That pic has basic editing with the iPhone adjustments. You can see the highlights are blown, and it's too dark now. In the eyepiece the view was WAY better than I thought it would be. When my son looked through the eyepiece he said "wow, that's high def!". Not sure if the mirror is actually decent, or if the increased f ratio (over my 4.5" f8) make the lunar view better? I look forward to pushing the mag to see what it can really do. 

 

Would making a simple aperture mask be beneficial for certain applications? 

 

Tenacious - here is a site that has the Odyssey manual on it with almost all specs listed: https://sites.google.../manual-page-13

 

The more I learn about the Odysseys, the more I think people sort of discount them as budget, or even cobbled together to make a buck scopes - when they were actually built in the spirit of John Dobson's low-cost, accessible, sidewalk astronomer, outreach mentality. The mirrors certainly have an inconsistent reputation, and I intend to find out where this one falls in the spectrum. I'll replace the focuser, and will rework the rear cell holder for ventilation and mass reduction - maybe a fan. 


Edited by lightspeed66, 12 June 2016 - 11:44 PM.

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#10 Tenacious

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Posted 13 June 2016 - 07:49 AM

 

"The more I learn about the Odysseys, the more I think people sort of discount them as budget, or even cobbled together to make a buck scopes - when they were actually built in the spirit of John Dobson's low-cost, accessible, sidewalk astronomer, outreach mentality..."

 

Yeah.   I think you found an excellent deal.

 

Have you built a base?  Pics?



#11 lightspeed66

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Posted 13 June 2016 - 11:08 AM

Tenacious - I just found it on Friday, I've only cleaned it and found info on it. Next step is focuser replacement, a finder, and a plan for redoing the mirror cell. I'm torn between removing material on the original, building a new one, or buying one like the University Optics ones. 



#12 starman876

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Posted 13 June 2016 - 12:22 PM

the moon looks good through most scopes.  Take a peak at Jupiter, Mars or Saturn and then tell us what you saw.


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#13 CHASLX200

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Posted 13 June 2016 - 06:07 PM

the moon looks good through most scopes.  Take a peak at Jupiter, Mars or Saturn and then tell us what you saw.

Coma heaven.  A Paracorr will clean it up.



#14 Terra Nova

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Posted 17 June 2016 - 12:38 PM

I am curious to know how you wound up mounting it? As I remember it, it came to you without the rocker box.



#15 lightspeed66

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Posted 17 June 2016 - 12:58 PM

Terra - It is still unmounted. I looked at the moon and Mars last night using my trusty "under the arm" mount. While unruly at best, I've grown to appreciate it's idiosyncrasies. Ha. I'm considering building a dob base for it, and still have a small ray of hope that they original owner may call after finding the original mount. 

 

Even better though, is an anonymous benefactor right here on CN has offered up an old, EQ column mount that's only missing the feet! I'm going to take up the offer and maybe use this for our Scout troop. I've ordered an inexpensive Crayford for it, and would really like to find a used 8" mirror cell to bring it into some form of usability. 


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#16 lightspeed66

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Posted 25 June 2016 - 05:27 PM

Since Terra asked, I'll follow up with the progress on the Odyssey, aka Thor.

Base in progress, everything is cut and shaped, just need final assembly and some paint. It's crude, as I did it as fast as I could outside with a jigsaw and belt sander. My regular shop is all full of audio and astronomy stuff being worked on! Also, I got the inexpensive RnP Chinese focuser installed.

 

gallery_258703_6178_691093.jpeg

gallery_258703_6178_670163.jpeg

gallery_258703_6178_1372131.jpeg


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#17 Terra Nova

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Posted 25 June 2016 - 06:36 PM

Looking good! I'm impressed!

#18 lightspeed66

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Posted 17 July 2016 - 02:21 PM

Final update in this thread instead of a new one.

 

Old Coulter 'hardware store materials' mirror cell (like 8 lbs or something):

 

gallery_258703_6178_995708.jpeg

 

And new University Optics budget cell:

gallery_258703_6178_1571361.jpeg

 

Other than some kind of decent end caps or fan or something, this is done. After I collimate it again and do some observing I'll make another post of what I find out. From what I've seen so far, I think the construction is VERY basic but solid. My gut says the mirrors and views are better than their reputations say they are, probably based on spotty quality and quality of the later mirrors. 

 

The side of the mirror has "-4" in a circle written on the side. Any mirror makers have an idea what that may refer to? 1/4 wave?


Edited by lightspeed66, 17 July 2016 - 02:21 PM.

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#19 clamchip

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Posted 17 July 2016 - 03:36 PM

In here there is a possible explanation of the edge markings:

http://www.askmister...ce.com/coulter/

 

I think the Odyssey gets a spotty reputation because the mirror is being suffocated

at the bottom of the tube, give it some air like you just did and it will reward you.

The thin Odyssey mirror curls up like a potato chip when its being tortured like that.

I'm not sure why the manufacturers sometimes choose to seal up the tube,

it doesn't make any sense to me.

They've closed up the tube in the past, and they are still doing it. If you read the

history books all kinds of ideas were tried, but its been known for a long time now that

a open tube is the way to go. I'd love to know what advantages there are to a closed

tube.

Here is a modern Orion cell, look familiar?

Robert

 

8 inch 009.JPG


Edited by actionhac, 17 July 2016 - 03:42 PM.


#20 lightspeed66

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Posted 17 July 2016 - 11:21 PM

Wow! Really? I thought that was strictly a Coulter thing. Between the plumbing focuser, the band clamp and the duct tape and staples, it doesn't seem like an optical instrument. After giving it a little love, I'm actually optimistic about it.

 

Thanks for that link. If that theory is correct, then it would be ~4% shy on focal length which ends up being ~900mm, and closer to f4.4.

 

What I'm most surprised about is that I thought these mirrors were spherical and likely 1/4 wave. Paraboloid and claimed 1/8th wave makes me even more optimistic. Feeling pretty good about my $10 garage sale find.


Edited by lightspeed66, 17 July 2016 - 11:22 PM.


#21 DozerCSX

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Posted 07 May 2020 - 11:52 PM

Just saw this - welcome to the Wonderful World of the Odyssey 8! I bought mine in 1988 and it's been my constant companion ever since. Mine is strictly the original (even with the  Telrad finder scope, which still works perfectly) I've never upgraded a thing, like a time machine (but then that's what they are, right?) The original 27mm Kellner was the eyepiece from a pair of binoculars - it has the plus and minus adjustment marks on the side! Perfect.

 

Wow, you did some real hot-rod upgrades - it would be interesting to see what kind of difference they make "where the rubber meets the road"... 

 

Here's an Odyssey trick - for planetary work, cut a piece of cardboard into a circle which matches the primary opening, then cut a 2 inch offset hole in that (which avoids the secondary mirror and supports) then hang it with a piece of velcro from the rim - voila! You now have a KILLER Herschelian unobstructed 2 inch/50mm, 800mm focal length (that's f/18 BTW) reflector, which works high power up to the limits of the alt-az stand. And it works like a dream (if, of course, your dream is a 20lb 50mm telescope!) But it slays for the moon and planets...

 

Anyway, these Odysseys are bulletproof, awesome, and at any moment put you FIVE minutes away from looking through the eyepiece.  Which you just can't beat.  This thing is a member of the family, and heck, my wife wouldn't let me get rid of it even if I wanted to!

 

It's even 100% American designed and manufactured and assembled. Good stuff.

 

Enjoy...

 

p.s. I have the original manual for the Odyssey 8 - if you're interested, let me know and perhaps I can create an e-version for you.


Edited by DozerCSX, 07 May 2020 - 11:57 PM.


#22 DozerCSX

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Posted 08 May 2020 - 03:19 AM

Here are some pix from tonight's Odyssey 8 Lunar observing in Herschelian mode:

Primary 200mm, off-axis stopped down to 65mm, 900mm focal length --> f/14

1st picture is w 17mm Plossl --> 52x

2nd picture is w 10mm Plossl + 2x Barlow --> 180x

3rd picture is Dob in Herschelian mode

 

This baby still rocks!

Attached Thumbnails

  • Moon at 52x sm.jpeg
  • Moon at 180x sm.jpeg
  • Odyssey 8 Herschelian Mode sm.jpeg

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#23 oldmanastro

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Posted 08 May 2020 - 10:55 PM

The Coulter 8 is a very good telescope. I had the f/7 version back in 94 and saw the Shoemaker-Levy comet impacts with it. The optics were excellent. It was also my first encounter with heavy tube currents. The first time I took it out stars looked like comets. At first I thought it was the optics and even talked with Coulter about it. In the end the telescope needed a long time for thermal stabilization due to its completely enclosed mirror cell. While stabilising you could place your hand inside the tube, rotate it and see the disruption of the thermal column.  After stabilization the images were as good as they can be. It was a real pain to collimate with that original and crude wood mirror cell. In the early 2000s an opportunity came up for a GP-C8 and I sold the Coulter. It was an optically very good no frills telescope and a pleasure to use. 

 

Clear Skies!

 

Guido


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#24 clamchip

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Posted 09 May 2020 - 10:01 AM

The Odyssey is one of my favorites.

I thought I'd show a simple solution for the little f/4.5 munchkin.

I miss you Stumpy!

Sorry I let you go, us humans aren't the brightest.

Robert

 

post-50896-0-82390100-1572720689.jpg


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#25 lightspeed66

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Posted 22 May 2020 - 07:51 PM

Well look at you guys, resurrecting a 4-year old post. My other hobbies have been taking over my astronomy time, but here’s an update of this OTA. Some time ago I picked up a three-vane spider to put in place of the weird Coulter fixed steel bar thing. Once I get that in, we’ll really see what it can do.

I’m still stunned looking at that moon picture I posted. That was hand holding it in my lap, and holding a phone up to the eyepiece.
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