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Meet the Problem Child

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#1 clamchip

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Posted 07 November 2021 - 04:54 PM

Friend and fellow Cloudynighter Doug (DouglasPaul) asked me if I wanted to adopt his red tube Coulter Odyssey 10.

He'd had enough of the problem child.

"Won't hold collimation, focuser's got problems, I'm moving, no place to store it, I've had enough of my problem child."

He gave it to me, and even loaded it into my car for me !

He knows I really like Coulter's Odyssey, and I'm always up for a telescope project.

Thanks again Doug !

Doug had let me know beforehand why she's a problem, "it's the back of the mirror, it isn't flat" and now that I've seen

the problem myself it does have me scratching my head too.

Its my understanding the Pyrex came in sheet form to Coulter. The sheets were cut in 6 foot lengths, probably while still

molten, to make them easy to handle. Doug's, and now my mirror, came from the end of one of these sheets. The sheet

must get stretched or squished when the cut is made my guess.

Because of this thin side it won't contact the cell floatation pads evenly. I'm going to really need to think hard about

this, it's definitely NOT in Sam Brown's All about Telescopes ! or anywhere else for that matter !

Oh the fun, Oh the horror, I love it !

Robert

 

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#2 clamchip

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Posted 07 November 2021 - 04:56 PM

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#3 Russell Smith

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Posted 07 November 2021 - 05:46 PM

https://www.google.c...ile-gws-wiz-hp#


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#4 Sincos

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Posted 07 November 2021 - 05:52 PM

Holy “ barnyard droppings” Batman, how did the factory hold it to grind it ? Looks like someone at the factory did not calculate for the right amount of end scrap for the cuts needed. If it is anything like aluminum extrusion, you calculate how far in the deformation will go when the stretcher pinches and grabs the ends to stretch the still hot piece and still have enough usuable product to fill order.

 Got a stock Coulter 10 , my favourite scope, yours however has had many alterations and upgrades. Probably all in various attempts to placate the problem child . Maybe find some silicon or epoxy type product with close to same thermal expansion rates as glass and dam up the sides and pour a flat surface for yourself.

Good Luck and Clear Skies when it’s done.


Edited by Sincos, 07 November 2021 - 05:54 PM.

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#5 clamchip

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Posted 07 November 2021 - 07:13 PM

It could very well be when it left the factory on its particle board cell it was okay and a

previous owner upgraded the cell for other reasons. My worse fear is the uneven thickness

is creating a disfigure unless it is equalized.

It might have slipped off the test bench and out of the factory with a figure ailment unnoticed

but in the field it probably will never be perfectly equalized, ahead of the ambient temp or

chasing after it. And if that's the case even Batman won't be able to help me.

I've been studying the problem and I think I will place the thin part at 12 O' clock, and

a floatation pad at 12 O' clock, and the 3-points of this pad will almost be on the flat

area of the back. If that doesn't work I'll just keep dreaming up ideas and trying them out.

There is no time clock in my shop, I can't think of anything I'd rather be doing, so let

the games begin !

 

Robert


Edited by clamchip, 07 November 2021 - 07:33 PM.

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#6 DAVIDG

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Posted 07 November 2021 - 07:35 PM

 The problem is that the mirror is allowed to be free floating in the cell. If it was mine I would remove the mirror from the cell and set all three triangle supports to the same height. I would then apply RTV to each of the 9 contact point and lower the mirror into the cell. I would make sure the mirror doesn't tip so it is flat against the two triangle under the flat area on the back and there is enough RTV on the contact points of the triangle that is under the sloped section of the mirror to make contact

    Once the RTV has dried  the mirror can't flop around but it is still support at 9 points on the three main triangle supports and those supports are at the same height and flat  so when you adjust the mirror in  the cell will act the same as it would with a mirror with a completely flat mirror. 

   As I have said many time I would test both the mirror and the flat so you understand what you have and you don't waste time trying to correct a problem by  chasing an alignment issues when the problem is in the optics.

 

                          - Dave 


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#7 CHASLX200

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Posted 07 November 2021 - 07:42 PM

Never saw a blank like that hank. Maybe someone was drunk?  


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#8 clamchip

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Posted 07 November 2021 - 07:42 PM

Thats a great idea Dave.

You are saying allow the triangle supports to float or lock them down rigid?

I can prevent them from floating.

 

Robert


Edited by clamchip, 07 November 2021 - 07:44 PM.


#9 DAVIDG

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Posted 08 November 2021 - 09:32 AM

Thats a great idea Dave.

You are saying allow the triangle supports to float or lock them down rigid?

I can prevent them from floating.

 

Robert

 The triangle should pivot. They usually have a pivot in the center of triangle and a pin sticking  down off of one end so they can not rotate but cut swivel around the center pivot.  So you don't want to stop that motion.  Each triangle has 3 points of contacts at the ends for 9 points. So what I'm suggesting is that at each of these 9 points you place RTV to glue them to the back of the mirror. The RTV is flexible enough to still allow movement and to equalize the support of the glass put  the RTV with hold the mirror in place and keep the three triangles  from tilting too much from the one being in contact on an angle to the sloped back. The triangle under the sloped section will of course need larger amounts of RTV to fill in the difference in height caused by the slope of the back.  The key is that you glue the mirror in place with all three triangle being flat has they would if they were all against a mirror with normal flat back. I hope this makes sense.

 

               

 

                      - Dave 


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#10 clamchip

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Posted 08 November 2021 - 10:39 AM

It makes sense Dave and a very good idea.

I'm going to try the mirror and cell without RTV first, I just want to test it and look for

problems, and then I will RTV the 9 points to the mirror and let it cure a few days. 

 

Robert


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#11 clamchip

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Posted 08 November 2021 - 10:58 AM

I'm curious to try this twin semicircle curved spider.

If you click on the Ken Novak catalog page it will enlarge.

 

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Edited by clamchip, 08 November 2021 - 11:00 AM.

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#12 clamchip

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Posted 08 November 2021 - 11:05 AM

Does anyone recognize this vintage Crayford?

How about the ODYSSEY10 sticker? aren't they usually ODYSSEY COMPACT on the 10 inch?

 

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#13 ccwemyss

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Posted 08 November 2021 - 11:42 AM

I would check that the mirror has a good figure and no need of recoating before gluing it to the supports. RTV can be a hassle to cut through if the mirror needs to be worked on.

 

Can you temporarily attach a spacer with some double-sided tape? You could also cover the back with plastic wrap, make a dam around the edge, and pour resin to get a custom fill piece that's not stuck to the glass, but gives it a flat back. If it works, a dot of contact cement could hold it in place and still allow for differential expansion. 

 

Chip W. 


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#14 clamchip

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Posted 08 November 2021 - 12:49 PM

The mirror coatings are in great shape.

I'm going to test the whole scope before I glue it to the cell points.

I wish I owned a 10 inch flat, and its a bit big to use a pizza pan oil flat.

I will star test inside and outside focus, and with Jupiter and Saturn handy

I can see how good it resolves detail.

I should be able to see if the thin side of the mirror warps the figure with

a star test diffraction pattern. Its starting to get cold here and temps are

falling fast at night when it's clear. I really hope the thin side doesn't act like

a giant clamchip and curl the mirror like a potato chip, it would be just my

luck.

I'll try and determine if its the thin side or the cell if I see problems.

I'm betting the mirror is fine, Coulter never would have let this leave the factory

unless it was okay. I've owned enough of these Odysseys to know them

pretty well.

 

Robert


Edited by clamchip, 08 November 2021 - 12:54 PM.

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#15 DouglasPaul

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Posted 08 November 2021 - 01:52 PM

I wish you well on your new project Robert, will be following with interest. I don't foresee  having room for a large scope for a few years and it's nice to know the old yard cannon still has a chance to become functional.


Edited by DouglasPaul, 08 November 2021 - 01:53 PM.

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#16 DAVIDG

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Posted 08 November 2021 - 05:15 PM

 I would Foucault test the mirror just to see what the figure looks like and also test the secondary. A good primary and bad secondary can lead to confusion in a star test as to what is going on. Just like the other optics,  amateurs make the mistake that they believe the diagonal is actually optically  flat. 

   Here is  a picture of the diagonal that came out of my clubs 17" Coulter before I refigured it. Not very flat at all and after I fixed it. 

 

                      - Dave 

 

coulterdiagonalbefore.jpg

 

coulterdiagonalafter.jpg


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#17 clamchip

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Posted 08 November 2021 - 06:03 PM

I forgot about the Foucault test, I did build a tester and haven't used it yet, this might

be a good candidate.

I can test the diagonal but now I have the telescope all back together and collimated.

Its ready to go, now I just need a clear night.

Whoever built the scope, or I should say whoever did all the modifications to it, did a

fine job. The primary cell is carefully enlarged to fit the inside of the tube precisely so

the mirror is dead center. Same goes for the spider, very accurately installed and the

diagonal holder is right on center. No diagonal mirror offset, which I would expect to

see with this fast focal ratio, I will leave it on axis for now. 

I did my usual daytime test objects and the views put a smile on my face. Aperture is

a wonderful thing, that's for sure.

Robert

 

IMG_0542.jpg


Edited by clamchip, 08 November 2021 - 06:06 PM.

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#18 DAVIDG

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Posted 09 November 2021 - 03:49 PM

 The same  Ronchi tester that you have used for double pass can be used to test the primary in Foucault test setup. The  bands will curve and the shape will give an indication of the figure on the mirror. It won't tell you exactly how close to a perfect parabola the mirror is like double pass does but it will give over all indication of how smooth it is and if there are any zones. 

 

                  - Dave 


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#19 clamchip

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Posted 10 November 2021 - 11:11 AM

I'm ready to go with the scope, I just need a night with holes in the clouds.

If it fails the shakedown cruise I'm going to bench test and find out exactly why.

 

In here Rose City Astronomers Rosette Gazette November issue page 7 history of the Coulter Odyssey I

see a photo of a employee using what looks to me like ArmorAll on the azimuth bearing, I'm going to give

it a try.

I have no complaints about any of the bearings but I will welcome cutting butter with a warm knife on a

winter's morning:

https://static1.squa...696840/2006.pdf

 

Robert


Edited by clamchip, 10 November 2021 - 11:14 AM.


#20 DreamWeaver

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Posted 10 November 2021 - 11:44 AM

...

 

In here Rose City Astronomers Rosette Gazette November issue page 7 history of the Coulter Odyssey I

see a photo of a employee using what looks to me like ArmorAll on the azimuth bearing, I'm going to give

it a try.

...

A CN member had posted that he rubbed a bar of soap on the bearings.  I tried that on my blue tube 13.1 and it made a noticeable difference. 


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#21 clamchip

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Posted 10 November 2021 - 12:32 PM

The problem with ArmorAll is if it doesn't work it is difficult to remove. To try it out I

will need to do it. I have used Turtle Wax paste wax in the past and its okay, nothing

to write about though.

The side bearings on this scope are very nice, I wouldn't dare touch them with anything.

The azimuth is fine so far during daytime but high power night time might be a different

story, I read the article and saw the ArmorAll bottle and started thinking it may be the

factory recommended product.

 

Robert   



#22 Kasmos

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Posted 10 November 2021 - 03:29 PM

The problem with ArmorAll is if it doesn't work it is difficult to remove. To try it out I

will need to do it. I have used Turtle Wax paste wax in the past and its okay, nothing

to write about though.

The side bearings on this scope are very nice, I wouldn't dare touch them with anything.

The azimuth is fine so far during daytime but high power night time might be a different

story, I read the article and saw the ArmorAll bottle and started thinking it may be the

factory recommended product.

 

Robert   

ArmorAll is very slippery stuff.

I remember kind of yelling at my Dad when he thought he was doing me a favor by using it on my Harley Sportster's vinyl seat.

I felt bad about it later but had already found out the hard way how it made it very hard to stay firmly seated on a motorcycle.


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#23 izar187

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Posted 11 November 2021 - 07:47 PM

Very cool.

I believe the 8" f/4.5 were the Odyssey Compact.

The cells in at least some of the red tubes were not really flotation at all.

Three rubber pad supports with full perimeter capture by duct tape and a large hose clamp, holding the mirror to plywood disc. 

Not open at all, and with a completely masked edge, and double plywood under the mirror, with heavy sono tube ota.

Rather significantly insulated from/against dropping nighttime temperatures.

Thickness variations may not have mattered, as originally built. : )

 

And I just found the other recent Coulter and Odyssey thread, so my 2 cents here was nuttin' new to the original poster at all. : )


Edited by izar187, 11 November 2021 - 08:15 PM.

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#24 clamchip

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Posted 12 November 2021 - 11:47 AM

I don't remember seeing so much rain here in my entire years born

and living here in Seattle.

That must mean my new Coulter Odyssey is very very good.

I have it on a Harbor Freight cart and can roll it out and be observing

in 2 minutes.

Robert

 

IMG_0535.jpg


Edited by clamchip, 12 November 2021 - 12:03 PM.

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#25 DouglasPaul

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Posted 12 November 2021 - 01:24 PM

Looks like it needs a Telrad. cloudy.gif




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