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The Wilmington 16" Cassegrain Cave / Restore

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#26 TOM KIEHL

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Posted 21 October 2014 - 05:40 PM

Tom ,

 

 Do you get the DOME also ?


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#27 clamchip

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Posted 21 October 2014 - 05:43 PM

Wonderful! saving the telescope and being able to play with such a big serious instrument, what a dream come true!

 

Robert



#28 dgreyson

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Posted 21 October 2014 - 05:51 PM

Definitely you want the dome.   Awesome find Tom, I would love to help but that's beyond my commuting range.  Cant wait to hear what happens next.



#29 Bomber Bob

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Posted 21 October 2014 - 05:56 PM

And I thought Amazing Stories was just a TV show!

 

You are The Man, Tom!

 

Like a lot of CN/CT members, I'd love to be able to drive up there and help with your project.  Talk about classic telescope preservation -- this is off the charts!!



#30 CHASLX200

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Posted 21 October 2014 - 06:10 PM

Seems like the OTA and mount can be taken out out by two strong people.  Not sure about the pier as it has to be heavy.  The mount can be broke down into parts and moved as i have owned a 2.5" Cave mount years ago.  If i lived close i would sure jump in and help.  I never get any of the fun here in FL the land of no Caves.

 

Chas


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#31 turk123

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Posted 21 October 2014 - 06:15 PM

Since it is a dual focus scope, ie a Newtonian and a cassegrain, then that means the optics should be of the classic cassegrain design with a parabolic primary and hyberbolic secondary. Making a 16" f/4 parabolic primary is not easy, especially if you do it with a Foucault tester vs other methods. Then you need to make a 4" diameter convex hyberbolic secondary. That is even a more difficult figure to get right and to get the figure correct you need to use a Hindle sphere which in this case would require a 16" f/2 spherical mirror. On top of that you need to get the baffling correct and all the Cave Cassegrains I've seen had the baffling wrong which leads to washed out image at the Cass focus. On top of all that even if you have perfect optics you have to get the spacing between the primary and the secondary correct to get the most out them. All this can be fixed but you can't assume that what is in the scope now is right. My advice is spend the same amount of time making sure the optics are right as one does making the mechanical aspects of the scope right. That way you'll have both a pretty telescope to look at and also one to look thru.
The scope is now in the best hands I know of, of giving it a new life and making what might be wrong with it, right. Good Luck Tom. Tom Cave is smiling on you from up above !

- Dave

 

David

 

I have a coating company that said they will donate their services on this one, so the surface hopefully can be brought back.  As for the alignment, I'm flying you in on this one.  It certainly will be a challenging project.  I leave the optics to the best.  You!


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#32 turk123

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Posted 21 October 2014 - 06:21 PM

Tom ,

 

 Do you get the DOME also ?

 

The dome is probably worth $30,000.  I believe the college was trying to keep it at my advice.  They can put a small 10-12" cassegrain in there, wire it up to the lab below and keep all the computer geeks happing viewing images on computer monitors and no one has to venture up in the cold dome ever again. : )   Sad to say, that is what keeps todays students interested.  This old Cave was never gonna do it.  



#33 turk123

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Posted 21 October 2014 - 06:25 PM

Seems like the OTA and mount can be taken out out by two strong people.  Not sure about the pier as it has to be heavy.  The mount can be broke down into parts and moved as i have owned a 2.5" Cave mount years ago.  If i lived close i would sure jump in and help.  I never get any of the fun here in FL the land of no Caves.

 

Chas

 

What surprised me the most was the weight of the pier.  I was dreading the thought of trying to move that bulk.  Guess what.  The pier is the lightest component on the entire scope.  It is made from sheet metal just a little thinker than that of a car body.  A few struts inside in the right places and it is surprisingly light.  I bet I will be able to carry it out.


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#34 turk123

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Posted 21 October 2014 - 06:43 PM

Does anybody know how well the system is figured?

Some years past, While looking at a 10 inch, I had been warned by a couple people not to get involved with Cave Cassigrains,

I don't know how reliable the reports were but I trusted them at the time.

What a wonderful project to have and be a part of it's history. Turk as you surely know, we never really own a Telescopes, we are

simply their guardians for a short time. That's why I hate to see the guys that don't take care of equipment. You know what I mean,

The guys that Drill & tap, leave them sit outside unprotected etc. I have a friend like that. The Spray paint King. Making it "user friendly".

You are about to become my Hero if you can pull this off in the proper way! I cant wait for updates! I'll bet it smelled like an old Hay Loft up there.

Duane

 

I've read that also.  Part of the problem is as DavidG says, Cave didn't like baffles in his scopes.  Jeff B1 use to argue with Tom about this and Jeff knows cassegrains, believe me. 

 

The large cassegrains are said to have Tinsley optics.  Pretty respectable as JPL use them for most of their optics.  I think it has more to do with configuring the distances between mirrors. It is difficult and very touchy.

 

See:

http://www.alpo-astr...sh/Cass_Equ.pdf

 

He's here now in our forum if you want to ask any questions.   :bow:      Some of his equations scared me off long ago!


Edited by turk123, 21 October 2014 - 06:46 PM.

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#35 TCW

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Posted 21 October 2014 - 07:41 PM

 

Absolutely awesome! :waytogo:

 

Rather than starting a company and obtaining workers comp and all that you should consider hiring a rigging company to help move the scope. They know how and have all the insurance needed.

 

That is a possibility I have thought of.  It will still require me removing parts from the telescope just to get it apart. The mirror has to come out.  Counter weights have to be removed.  At a certain point, walking it down the stares becomes doable.

 

Your specialized knowledge will be essential to a successful move.  I wish I lived closer and could help.



#36 turk123

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Posted 21 October 2014 - 08:05 PM

 

Seems like the OTA and mount can be taken out out by two strong people.  Not sure about the pier as it has to be heavy.  The mount can be broke down into parts and moved as i have owned a 2.5" Cave mount years ago.  If i lived close i would sure jump in and help.  I never get any of the fun here in FL the land of no Caves.

 

Chas

Disassembling it could make it a two or three man job.  A couple of days to take it apart and a half day to load it up in a truck. Your plan has my vote!

 

 

Yea, but I may have to take the 20 ton press!  You never know.

 

Actually I think it will take almost a day to clean and set rigging.  I'm hoping as you say, two days to disassemble, and one more day to pack the trailer.  Of course I should allow for another several days in the hospital.  


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#37 Bomber Bob

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Posted 21 October 2014 - 08:09 PM

Of course I should allow for another several days in the hospital.

 

I hope not -- take care of yourself!



#38 terraclarke

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Posted 21 October 2014 - 08:13 PM

Tom, as I told you last summer when you first told me about the project, just let me know when you are going to be there and I will drive up and meet you. Its only a bit over an hour away from me.



#39 rcwolpert

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Posted 21 October 2014 - 08:31 PM

Wish I lived closer. I've worked on a few large university scopes before. Would be so much fun and interesting.

 

- Bob


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#40 Datapanic

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Posted 21 October 2014 - 08:58 PM

This is going to be a fun one to watch!  Lot's of bird poop but hardly any rust!  Get a couple gallons of EvapoPoop and it'll come right off!  Too bad nobody thought to covered it up when they shut down the observatory.  There's probably only a few of the huge Cave's like this still out there, waiting to be found. 


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#41 Chuck Hards

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Posted 21 October 2014 - 09:16 PM

If there were a pantheon of Great Telescope Restorers & Historians, Tom's likeness would be a huge marble statue at the center.   Well-done!


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#42 DAVIDG

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Posted 21 October 2014 - 10:08 PM

 The issue with the old Observa dome are  the wheels. They are 3.5" diameter rubber coated over metal and the rubber peals away.  The wheels are located along the rim of the dome and motor that turns the dome has 12" rubber coated wheel also in contacted with the rim. If just one wheel fails and you try to adjust the motor to turn the dome  you put too much pressure on the rim of the dome and pull it out round. Then of dome binds as it tries to turn. This maybe  what caused the observatory to stop being used.  On the A.I Highschool observatory that I helped restore this Spring I replaced all the wheels from ones sold by Grainger. It cost about $50 and that brought the dome back into perfect operation.

  Cave had a deal with Observa Dome back in the early 60's. Cave supplied the cassegrain scope  and Observa Dome the dome as a packaged deal.  As for the pier you'll have no problem moving it. As you said it made of sheet metal and looks to be the same one used with the schools 10" Cave. If that is the case it weights less then 100lbs. You'll be able to break the scope down into  very easily movable parts. I bet it will take only a few hours. Two people should be all that is needed to remove it and you won't need a crane. You'll be able to walk  the pieces out of the building.

 

                - Dave



#43 turk123

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Posted 21 October 2014 - 10:08 PM

Tom, as I told you last summer when you first told me about the project, just let me know when you are going to be there and I will drive up and meet you. Its only a bit over an hour away from me.

 

Thanks terra, when things start to happen I will give you a call.  Wear your steel toed shoes and bring the Evapo-poop.


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#44 turk123

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Posted 21 October 2014 - 10:30 PM

 The issue with the old Observa dome are  the wheels. They are 3.5" diameter rubber coated over metal and the rubber peals away.  The wheels are located along the rim of the dome and motor that turns the dome has 12" rubber coated wheel also in contacted with the rim. If just one wheel fails and you try to adjust the motor to turn the dome  you put too much pressure on the rim of the dome and pull it out round. Then of dome binds as it tries to turn. This maybe  what caused the observatory to stop being used.  On the A.I Highschool observatory that I helped restore this Spring I replaced all the wheels from ones sold by Grainger. It cost about $50 and that brought the dome back into perfect operation.

  Cave had a deal with Observa Dome back in the early 60's. Cave supplied the cassegrain scope  and Observa Dome the dome as a packaged deal.  As for the pier you'll have no problem moving it. As you said it made of sheet metal and looks to be the same one used with the schools 10" Cave. If that is the case it weights less then 100lbs. You'll be able to break the scope down into  very easily movable parts. I bet it will take only a few hours. Two people should be all that is needed to remove it and you won't need a crane. You'll be able to walk  the pieces out of the building.

 

                - Dave

 

Dave

 

there is a "handle" made of 1" rebarb at the very top of the dome (inside).  Can that be used to support a chain winch?



#45 Rich (RLTYS)

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Posted 22 October 2014 - 05:40 AM

Wow! Tom, all I can say is good luck on your newest project. You are one busy man. :waytogo:  :bow:  :cool:

 

Rich (RLTYS)



#46 turk123

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Posted 22 October 2014 - 08:42 AM

Picture on the roof.

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#47 roscoe

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Posted 22 October 2014 - 09:32 AM

Wowza!!!  So will this monster be set up at NEAF next spring???  wouldn't THAT attract some attention!!

 

So very good of you to undertake this project!!!!  Thank you!  and, watch out for your back, don't be hurting yourself carrying big stuff down those stairs....remember, that's what block-and-tackles are for.....

 

R



#48 DAVIDG

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Posted 22 October 2014 - 09:37 AM

Tom,
I won't try hanging anything off the Dome it is not that strong. I moved bunch of heavy stuff in my life including telescopes and I'll bet when you break the scope down, you'll find that the heaviest part is going to be the Dec housing and the counter weights and both the these can be hand carried by two guys.
If it was me I would take the scope apart in this order

1) Pull the OTA off the mount.
2) Pull the primary mirror cell with the primary out the OTA
3) Pull the counter weights off the Dec shaft
4) Pull the dec shaft/tube cradle out the Dec housing
5) Unbolt the RA housing from the pier
6) Unbolt the pier from the base

All the parts should now be less then 100lbs each. You might run into a problem getting the counter weight off the Dec shaft. If that happens, I would take the RA drive off and pull the Dec assembly with the RA shaft attached. That would you be the heaviest part and still two guys can handle it.
If the school wants to restore the dome, like I said we did the same one at the local highschool for about $200 which included all new wheels and painting the inside. As I said Grainger sells the 3.5" wheels. I unbolted the old ones, removed the new wheel from their brackets and installed them in the old brackets. We used a 6' bar to left the dome up at each wheel position and then slipped in two blocks of wood to hold it up It took about two hours to replace all the wheels. Once that was done we recentered the dome on the building and adjusted the wheels that push on the inside of the rim so the dome was round again. Then I adjusted the 12" rubber coated wheel and motor so the dome would rotated smoothly.
As for the shutters, two of the pulleys had failed. It seems that they used metal pulleys but the pulleys had a fiber type material as the center hub which just fell apart. I replaced them with heavy duty garage door pulleys and reinstalled the cabling. You just have to adjust the cabling so that door open and close uniformily.

- Dave

#49 turk123

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Posted 22 October 2014 - 10:31 AM

That all sounds easy David but we are dealing with 100 lb. items 10 feet in the air let alone that they have not been apart since 1964.   If I can remove the guide rings and focusers from the OTA and get a strap on the tube, it would be nice to lower it to the ground slowly with a winch.  The dome is double walled aluminum or galvanized steel.  You don't think it would hold the chain winch and a hundred pounds?   I do have a call into observa-dome to ask their opinion.  

 

Alternatively, I could bring a few 2 x 4's with me, assemble them onsite (double them up to 4 x 4's)   to support the top of the dome.  I just feel that a winch will give me more flexibility with less injury to me and my workers.

 

 

There is a steel rolling stepladder in the dome.  I'm on it in this picture looking down at my friend David.

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Edited by turk123, 22 October 2014 - 10:32 AM.

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#50 orion61

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Posted 22 October 2014 - 10:38 AM

You are going to have to come up with a good Nick Name for it when done..




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