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8" Odyssey Dob with "2 inch pipe thread mount" in the focuser hole? Mirror looks good too?

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#1 Craigar

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Posted 24 July 2021 - 05:00 AM

I'm a newbie to "serious" astronomy so please forgive my wild guesses, and I really appreciate any help and insights. Maybe they had a camera hooked up (or were thinking about using it as a small boiler tank LOL) or some kind of a (now MIA) screw on focuser? Or someone absconded the focuser and wanted to leave it looking sort of pretty? What would be a decent middle of the road focuser to use? Coulter seems long gone out of business also.

 

I rigged up a few wraps of velcro around the long barlow that came with this and tried with the included "27mm Kellner-Binocular surplusr" and "Parks K12mm" eyepeices and it seems really good, I can see Jupiter pretty clear and the moon with extreme detail.

 

The primary mirror looks really good to me (although it was dusty) and has 2 minor imperfections in the coating (2 that are smaller than a grain of fine sand and close to the edge) - even though Coulter's docs say the coating should only last 10 years? Are their obvious ways I would be able tell if the mirror needs a recoat (other than comparing to another known good similar sized newt)

20210721_170954~2a.jpg 20210715_214653~2.jpg

 

Thank You All!

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Edited by Craigar, 24 July 2021 - 07:01 AM.

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#2 Craigar

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Posted 24 July 2021 - 05:19 AM

Here's a couple of test shots using my Olympus micro four thirds with a Olympus 70mm f1.8 lens trying to focus in real time - I was in a parking lot looking towards a "Target store sign" and the 1st shot is using a 25mm lens through just the camera and the 2nd shot is the same lens up against the focuser hole (with my fingers as "suspension pads" to reach and half arse hold focus. I was using the cameara in "auto exposure/focus + IBIS stabilization" mode also, other wise my hand shake would have made it a blurry mess.

 

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#3 Sincos

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Posted 24 July 2021 - 06:05 AM

Greetings and salutations Craigar welcome to CN. The old Coulter Optical units were made of mostly pre-existing parts, like for instance your focuser. Have a close look do you recognize any of the fittings? Ever done any home plumbing like installing a new kitchen or bathroom sink, that is where the focuser parts came from, no really. Looking at yours it seems the aluminum tube that held the eyepiece is missing , it can be substituted. Check out the pics below and see how the focuser was remounted on mine. Got this one for my sister and niece but needed some work. Had to remove then reinstall focuser, now held in place by Goop ( shoe repair stuff ).  The extra unit sitting on top of scope is the IPEX  plumbing fitting that was used. Go take a walk down the plumbing fitting aisle at Lowe’s or Home Despot and see what is there to complete yours.

 Good luck , they are great scopes, have fun. Would not worry about the the coatings on mirror until you can tell they are having a detrimental effect on image. Anotherwords can you notice it when looking through eyepiece or does it show up in picture. Half arse is better than no arse.  ; )

 Clear Skies

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Edited by Sincos, 24 July 2021 - 06:40 AM.

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#4 Craigar

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Posted 25 July 2021 - 06:05 AM

Thank You Vostok 1!

 

I was almost certain it is ABS or PCV 2" pipe thread, just didn't seem like it would be "stock" but I can understand why  - because the quality of the mirrors are really good and it has been getting progressively harder to make a profit when making something really good and low priced here in the U.S. so they had to cut some corners. So does yours have some focus beyond pulling the pipe in and out i.e. do you rotate it and and have the pipe threads working as a "helical focuser"?

 

I really got a laugh out of this site being called Cloudy Nights because their sure are way more of them then I realized - and tonight was another one! I wanted to view the "buck moon" but no cigar. Soooo I decided to check the collimation using an "artificial star" - I heated up a safety pin and went through the top of a plastic spice jar lid and stuck it on top of a LED flashlight and got it about 100" away and used a 6.5mm eyepiece blurred in the positve direction - this is an image I took with my Olympus micro four thirds with a kit lens at about 40mm - so it looks like I'm out a little but I didn't want to mess with screws to adjust the primary cause I don't know what I'm doing  - looks like 3 sets of 2 screws in each, in a triangle

 

Thank You everybody!

 

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#5 Craigar

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Posted 25 July 2021 - 06:14 AM

here's a pic of the collimation taken with my cellphone

 

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#6 Sincos

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Posted 25 July 2021 - 08:08 AM

Yes Craigar, to keep the costs down these Coulter scopes did not even include a finder scope in the package. The mount did not use good plywood but rather cheaper particleboard all to keep the price of larger optics accessible to more people.

 Until you get the focuser sorted out do not try to collimate . So from your pictures the fittings that are missing are the aluminium tube that actually holds the eyepiece and the compression fitting that screws onto the existing threads on the scope. These parts when assembled become an Helical focuser , should you choose to read up on them. The missing aluminum tube is 3.25 inches long and has an inside diameter of 1.25 inches to accept standard eyepieces.  Whatever tube you choose to use in this position should have the ability to have a set screw drilled or tapped into it to hold an eyepiece in place. Notice the white “O” ring in the top of focuser this is the compression fitting that holds the eyepiece at the correct distance to focus the image. Do not know what your ability to source parts are but have heard of some people using the metal tube from a vacuum cleaner as an eyepiece holder. Anyways , hope this and the attached pictures help to sort this out for you. Post any further questions here and someone will answer.

 PS. That dark line in your collimation pictures is the secondary’s support structure, that black bar holding the secondary mirror in place.

 Clear Skies

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Edited by Sincos, 25 July 2021 - 08:11 AM.

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#7 Bomber Bob

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Posted 25 July 2021 - 08:37 AM

If it was BB's scope:

 

- I'd buy the plumbing stuff to star & sky test.

- If Good Mirrors, I'd put a nice low-profile 2" R&P Focuser on it -- looks like the hole is already wide enough for a 2" version.  I did this with my Edmund 6" F4 Newt, and Mercy!  With it's 2" Paracor, it's a blast -- wide fields with sharp stars...


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#8 Terra Nova

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Posted 25 July 2021 - 08:45 AM

Forget a telescopic finder scope. It’s begging for a Telrad! One would be perfect for it.


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#9 Sincos

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Posted 25 July 2021 - 09:40 AM

Yes , definitely Terra Nova. Telrad is the best way to go with a Coulter !


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#10 Tenacious

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Posted 25 July 2021 - 10:03 AM

Great telescope for trying out "serious" astronomy!   I think your scope is now considered a classic - do you want to keep it as close to factory-original as possible?

 

+1 for BBs suggestion.  Low profile, rack&pinion focusers are inexpensive and plentiful.  You simply need to determine how much travel above your telescope wall is required for your eyepieces to reach focus.  Most are going to be in the same ballpark, say all within about a 1/2" range.  When selecting a focuser, try to avoid having excess draw tube length extending down too far into the scope and remaining in view of the primary light path when focused.

 

Terra nailed it.  It looks like the previous owner had a Telrad on there - the black base appears to be installed in your second image.


Edited by Tenacious, 25 July 2021 - 10:08 AM.

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#11 Sincos

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Posted 25 July 2021 - 10:18 AM

Great eye for detail Tenacious , had not even noticed the base of what appears to be a Telrad mounted on the scope. So Craigar , even if you did not get a Telrad in the deal the mounting plate for one is there, so why not use it. Telrads show up here in the classifieds regularly just keep your eye open for one when it appears and snap it up.

 Since we are talking about telrads must also mention Harvard Pennington’s book on Messier Marathon worth having since it uses a telrad to find all Messier objects.

 Clear Skies all


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#12 Gil V

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Posted 25 July 2021 - 02:14 PM

Any red dot finder works. FOV is ginormous.

#13 Craigar

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Posted 25 July 2021 - 04:27 PM

Yes!, it came with a Telrad (and 3 eyepieces) which my newbie brain perceived the Telrad  as funky/cheesy (contempt prior to investigation..) - until I cleaned it up and got fresh batteries - "slicker than owl *%#$!" and got it actually reasonably aligned using the "target Store" sign (on the first night after I bought the Odyssey) but it ran out of adjustment travel - which was my 1st clue that it probably needs collamation (or the guy stuck the rails on a little skewed) -  also very cool how looking down from the top we can see the desired star and bullseye too (even though flipped - but, that matches the scopes view better too)! Just like me, it works almost as well "bassackwards"..

 

Thanks!


Edited by Craigar, 25 July 2021 - 11:24 PM.


#14 Sincos

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Posted 25 July 2021 - 06:08 PM

Hey Craigar , those circles on the Telrad are actually calibrated to aid in locating what you want to see . For instance the outer ring is a two degree circle the next is one degree in diameter and the smallest is 1/2 degree ( just fits the full moon ). Now if you are travelling old school , charts and star hopping , some charts/maps actually come supplied with see thru overlays of Telrad circles to aid in navigation,  SkyAtlas2000 for instance and the aforementioned The Year-Round Messier Marathon Field Guide. See below for example 

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#15 Craigar

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Posted 25 July 2021 - 11:21 PM

Oh yea - I'm traveling pretty old school although I got a pretty decent smart phone - but no fancy "GoTo" gear yet (don't have a burning desire but this too could change, cause a got going up this Astronomy tree "just" trying to get real good photos of our moon) - and I have a 4" Fecker newt on a EQ fork mount with a motor (that the 2 conductor AC cord was cut off, so it may have been a discard from public school (found set out by someones trash cans about 15 years ago - info on it says it's from 1954) and it's mirror is pretty good - but not as clean as this 8" Odyssey...

 

I got this Celestron Sky Map "star chart" book as part of a package deal that I got on a Celestron "Premium 80" with Alt-AZ mount on a pretty nice wooden tripod - but I don't understand it yet and really haven't had good enough skies at a time where I could check it out yet?  Very Good that they use 2 degree "Telrad" circles on the SkyAtlas2000 and The Year-Round Messier Marathon Field Guide. But I have been able to get my brain to digest / connect/ relate with much of it yet

Thanks!

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Edited by Craigar, 25 July 2021 - 11:23 PM.


#16 Craigar

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Posted 25 July 2021 - 11:36 PM

and was checking the collamation with a 45 diagonal with 3 even wraps of velcroe stuffed tight into the focuser "pipe" hole butted up against it ledge with a 6.8mm eyepiece centered on it held in alignement with a piece of packing tape wrapped around it in a "U"  so I think it's pretty good "ball park" but not precise enough to justify trying to collimate yet

 

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#17 Sincos

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Posted 26 July 2021 - 06:01 AM

Sooo , have you thought about placing a classified ad here on CN looking for the  tube for a Coulter helical focuser ? Never know your luck in the big city. Just in case you are wondering about how the focuser works,  the missing aluminum tube is held in place by the white compression ring in the missing plumbing fixture. Simply screw down the internally threaded part until it grabs the aluminium tube enough to hold it in place at the desired height . If you get it just right you can still adjust focus by lifting up or pushing down on the tube when changing eyepieces.

 Good luck and please post updates along the journey.



#18 clamchip

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Posted 26 July 2021 - 09:20 AM

Keep a lookout for the Lumicon focuser too:

https://sites.google...y/modifications

 

Robert


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#19 Sincos

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Posted 26 July 2021 - 10:53 AM

Well thank you clamchip , had not known of this site. Craigar you now have the means to accomplish what you want.


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#20 Tenacious

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Posted 26 July 2021 - 12:05 PM

Keep a lookout for the Lumicon focuser too:

https://sites.google...y/modifications

 

Robert

Nice link, Robert!  All of the modifications were thoughtful improvements over the original.  It does make me appreciate Coulter's apparent design philosophy, "..put largish aperture on a stable platform and get more people under the night sky for an entry level price..".   Very admirable.


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#21 Craigar

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Posted 26 July 2021 - 04:41 PM

Thank You Clamchip!  Nowadays I often "miss trees when looking through a forest" (I'm 65 and now have a thorough understanding of why not working 8 hour days or Retirement make sense , I'm even lucky to be able to do 3 or 4 productive hours sometimes))  cause I had found this link a week ago here at CN (when just curious about the specs, etc.) but *forgot* to check out the modification link. This has got good solutions for many of the "economy design" problems.

 

Last night I got about 3 minutes (in between little puffy clouds with one good clear opening proceeding into to a thick solid cloud blanket= done for the night) of the most detailed live moon view I've ever seen even compared to some of the deeper pixel peeps of seen on my PC  - and I imagine a lot of it is dynamic range of the actual real light and mirror - and I was using the homemade "unobstructed view aperture reducer" that came with this scope as shown in this pic! Thank You;

20210726_140554_HDR-crop.jpg


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#22 Craigar

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Posted 28 July 2021 - 08:28 AM

I learned - from the original "Odyssey 8" that this cardboard "unobstructed view aperture reducer" as I called it is actually makes a newt into a "Herschelian telescope" also known as a "OFF-AXIS APERTURE STOP"  really really good for the moon (which is already too bright.). He explains how to simply make one (for this or any newt) - once again, as often times "Less is more.." and than my eyes can adjust quicker to low light viewing, which will be best full aperture on most cases.

 

https://sites.google...y/manual-page-5


Edited by Craigar, 28 July 2021 - 03:57 PM.


#23 DAVIDG

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Posted 28 July 2021 - 06:29 PM

 A minor correction, the mask turns the scope into an offaxis Newtonian. In a Herschelian the whole  primary is tilted  to move the focal plane out of the light path. The problem is that when you tilt the primary you introduce astigmatism into the image. Your actually mis-collimating the primary.  To have a diffraction limited image the focal length must be very long and the angle that the primary is tilted is very small. In many cases 1 degree or less.

   In an offaxis Newtonian, it is using a section of a larger parabolic primary. The mirror is not tilted  to the incoming light but because it is off axis segment and  it reflects the light off to the side so the focal plane is out of incoming light path. 

  When you use an off axis mask you remove the diffraction effects of the secondary and reduce any optical error in the primary but you also reduce resolution.  

 

                 - Dave 



#24 Craigar

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Posted 30 July 2021 - 05:15 AM

Thank You DAVIDG, what you said sounds more accurate to me, I appreciate the clarification


Edited by Craigar, 30 July 2021 - 05:15 AM.


#25 Craigar

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Posted 16 August 2021 - 06:51 PM

Got a Tectron 2" R&P focuser seems very nice but maybe too big for this scope? it needs a 2-1/2" hole - I bet it is from a 12" newt? My Odyssey 8" has a 1-7/8" hole for it's friction focuser. Here's the CN ad I bought it from https://www.cloudyni...p-newt-focuser/

 

My diagonal mirror is only 2" short axis so probably max viewable image diameter is 1-5/8"? Did/do they make any popular focusing system between 2" and 1-1/4"

 

Lately I'm onto a "Meade 2045 102mm SCT" tangent partially cause my knees and back weren't used to this Dobsonian Yoga Origami workout routine and I wanted something that would some what track for astrophotography (and don't have a big budget) ... here's my take on it so far.. https://www.cloudyni...45-4-sct/page-2  and it's giving me a different type of work out and I have the "original Meade field tripod" jacked up on pans with wooden furniture wedges and 2x4's etc.cause theirs no leveling adjustments and was a little to short for my height and this relatively small scope - and the clutch in the AC drive is sketchy so I keep having to do fine tracking by moving at least 1 tripod leg ... I'm sure many of you know what I'm talking about

 

I am also  going to need to "redo" this Odyssey's dob mount so it's smoother and easier to control when chasing planets, etc. - I'll be back

Thanks!


Edited by Craigar, 16 August 2021 - 07:28 PM.



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