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Mr Magoo's Cave

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#101 CHASLX200

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Posted 07 December 2018 - 06:45 PM

I know Cave was using any tubes they could get near the end. Paper wound tubes and Meade Fiberlites.


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#102 Mr Magoo

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Posted 07 December 2018 - 11:54 PM

Ken - no.  That is the Cave I got in 2012 from a fellow CNer in upstate New York.  It dates to March 1979...the optics are very good; the tube is a Sonotube, focuser is a 2"/1.25" Meade, the declination drive uses a segment arm, and the setting circles are Bakelite.  The mount and the pier are in excellent condition, and the legs are set up on casters...so I can roll it out of my garage on demand.

 

The Cave I've mentioned on your topic dates to mid-1975...was privately owned, then donated to a university from which I purchased it (they had used it for several decades).  Haven't star tested it yet.  The tube is a Parks product, focuser is 1.25" only, the dec drive uses a shaft mounted gear, and the setting circles are engraved aluminum.  It came without a pier or legs, but the university threw in three very large Edmund Scientific legs (probably from a '60's vintage 8" reflector that they no longer have). 

 

attachicon.gif new Cave tube.JPG

 

John

Very nice!



#103 Mr Magoo

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Posted 09 December 2018 - 12:46 AM

Well, I made a rather embarrassing mistake. As a sheet metal worker for more than 30 years I should know better than to trust someone's measurements.

 

I cleaned carpets most of the day and was relegated to the garage while they dried. To keep myself occupied I decided to finish stripping the OTA of all its accessories. As I removed the end rings I thought boy that tube looks bigger than the 14.5" that I was told. Grabbed my tape and lo and behold it is 15 5/16" O.D! I felt pretty darn stupid at that point and checked it a few more times. I figured out that they were measuring the inside of the end rings.  

 

My apologies to everyone for getting it so darn wrong. Still can't believe I did that. I'm always preaching to my guys to never trust anyone's info, not even mine. Measure twice cut once right? I took two showers to get the egg off my face. 

 

So as Paul Harvey would say, now for the rest of the story. My tube is 15.3125" O.D. as I just mentioned and the I.D. of the rotating rings are about 16". Now I see why they had to use the 16" rings. My question now is is this normal to have a tube over 15" O.D. with the rings 16" and a bunch of shims? Mine was shimmed with some sort of white plastic about 3/16" and 1/4" thick cork. 

 

What I think I will do when I put it back together is to fabricate a shim from aluminum flat bar and attach it either to the tube or the ring and then use a strip of cork to fill the rest. I thought that if I attached the flat bar ring to the OTA then I could put the rings on without the worry of marring the tube. 

 

Oh and I haven't counted them yet, but there are a bunch of extra holes in this tube. The oddest ones are on the rear end in line with the mirror cell holes, but more than 12" away from the end. Maybe they had a shorter focal length mirror in it at one time, who knows. 

 

I have identified what a lot of the others are for. I am missing one counterpoise bracket. Don Rothman may have one in his warehouse of stuff. 


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#104 Geo31

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Posted 09 December 2018 - 08:55 AM

Ken, the tube diameter you have is not standard,  As others have said, apparently Cave had to get more creative in sourcing in the later years and I suspect that is the issue here.

 

The shims you describe should work fine.  I assume you’ll add some curvature to them.

 

I would assume the second holes for the mirror cell were for imaging (move the mirror up), but 12” seems extreme.  How far up are the “normal” holes?


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#105 CHASLX200

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Posted 09 December 2018 - 09:31 AM

Ken, the tube diameter you have is not standard,  As others have said, apparently Cave had to get more creative in sourcing in the later years and I suspect that is the issue here.

 

The shims you describe should work fine.  I assume you’ll add some curvature to them.

 

I would assume the second holes for the mirror cell were for imaging (move the mirror up), but 12” seems extreme.  How far up are the “normal” holes?

I saw a late 70's 12.5" F/5 Cave with a spiral wrap inside the OTA many years ago.  I think it could have been a Meade Fiberlite tube.  Parks always seems to have a rough inside with a clean seam and have that Parks smell that not other tube maker gave us.  I know that Parks smell a mile away. Even tubes that are 50 years old have that Parks smell when ya stick your head in there and sniff.

 

Guess i am a tube sniffer. Better than glue sniffing i guess.  Seems tube OD's also would vary by maker and years that Cave used.  All in all it seemed Cave used Parks until around 1976 then it was all over the board.

 

As for extra set of mirror cell holes, 1 to 1.5" seem to be the norm that i have seen.


Edited by CHASLX200, 09 December 2018 - 09:32 AM.

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#106 Mr Magoo

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Posted 09 December 2018 - 12:44 PM

Ken, the tube diameter you have is not standard,  As others have said, apparently Cave had to get more creative in sourcing in the later years and I suspect that is the issue here.

 

The shims you describe should work fine.  I assume you’ll add some curvature to them.

 

I would assume the second holes for the mirror cell were for imaging (move the mirror up), but 12” seems extreme.  How far up are the “normal” holes?

I will get a piece of aluminum flat bar and roll it up to the correct I.D. 

 

The mirror cell holes closest to the end are right at 2". There is another set at 3.375" and then the other holes that line up with them are at 14.5" from the end. 

 

I counted all the holes (including the focuser hole) in the tube and the grand total is 65 holes! What the heck lol! So what is the best method to fill holes in a fiberglass tube? 



#107 TOM KIEHL

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Posted 09 December 2018 - 03:00 PM

 So what is the best method to fill holes in a fiberglass tube? 

 

I use this https://www.smooth-o...products/mt-13/  with blue painters tape to back up the hole on the OD. and fill the hole from inside .  Can't reach the inside ? ..... put a glob of mixed epoxy on sticky side of blue painter tape , and press into hole and smooth tape over till hard , then remove the tape .

 

 

The best part of this product is IT'S WHITE !
 


Edited by TOM KIEHL, 09 December 2018 - 03:02 PM.

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#108 CHASLX200

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Posted 09 December 2018 - 03:31 PM

I use this https://www.smooth-o...products/mt-13/  with blue painters tape to back up the hole on the OD. and fill the hole from inside .  Can't reach the inside ? ..... put a glob of mixed epoxy on sticky side of blue painter tape , and press into hole and smooth tape over till hard , then remove the tape .

 

 

The best part of this product is IT'S WHITE !
 

So how do you order it? I sure don't need a big bucket of it. 


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#109 TOM KIEHL

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Posted 09 December 2018 - 03:46 PM

So how do you order it? I sure don't need a big bucket of it. 

Duh foreheadslap.gif ohmy.gif  https://www.amazon.c...e/dp/B06XGNC42B



#110 CHASLX200

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Posted Yesterday, 06:22 AM

Perfect. Better than caulk.


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