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Restoring a '59 Cave 10" f/7.1

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#126 Guy Earle

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Posted 20 April 2019 - 09:25 PM

Pic 2 of 3.

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#127 Guy Earle

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Posted 20 April 2019 - 09:26 PM

Pic 3 of 3.

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#128 Guy Earle

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Posted 21 April 2019 - 05:58 AM

Okay, I have a bit more to report since I went out this morning than after sunset last night (see page 5). Ironically, I really didn't get to test the mirror until the 21st, so it really did get its 60th second light.

 

The drive works smoothly and tracks well despite the declination needing about 14 degrees adjusted. My biggest issue, that makes the scope difficult to use, is what seems to be slop in the right ascension. I have to go past an object about 5 degrees until I feel resistance, then let it fall back into view. I can slowly pull the object into view, but not in the other direction. There's no knob to tighten it down, and I was working on the balance making small adjustments on the counterweight, but it never got rid of the slop. 

 

Can you all offer suggestions? Am I just not balancing close enough? Is there something with the gears or a means to tighten it that I have not done?

 

Thanks, and I've attached a couple lunar pics I took with my phone at the eyepiece. To the eye the Moon was crisp, but the phone was being difficult through the eyepiece.

 

Guy

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Edited by Guy Earle, 21 April 2019 - 06:00 AM.

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#129 Guy Earle

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Posted 21 April 2019 - 10:45 AM

Update: so I checked this morning, doing the initial balancing and looking for anything shifting with the tube and counterweight lateral to each other. I took the cover off the motor and three screws had come nearly out on rear plate, two on top and one underneath the shaft. Tightening those up got rid a vast amount of the sloppiness. Are there only three? I see other holes, and I'm wondering if other screws had worked themselves out over the years.

 

Guy

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Edited by Guy Earle, 21 April 2019 - 10:46 AM.

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#130 KentTolley

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Posted 21 April 2019 - 12:04 PM

Those 3 screws attach the rear plate, as you call it, to the polar housing.  It is actually the cover to the clock housing  But loose you would get vibration in the mount.  To your 2nd question, yes.  Any loose screw is nfg.  Check them all.   Legs, pier, pier cap, mount, saddle, rotating rings.  Lift the tube in its rotating rings to check any looseness at the pier cap.  One9 of my scopes is loose there now and I didn't notice it till I checked for too much slack in the rings and the entire mount rotated about the big bolt and nut in the pier cap.  For 50-something years it has only been the weight of the dec axis that has held the whole thing from rattling  around.  

 


Edited by KentTolley, 21 April 2019 - 12:39 PM.

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#131 tim53

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Posted 21 April 2019 - 12:23 PM

Since the back plate supports the worm block, there will be movement of the worm block and that could easily add up to quite a lot of slop in RA.  once you get these and other mounting srews snug, make sure the scope is well balanced, and adjust the clutch for the RA until you get just enough tighness to hold the scope in position but not so much that it's hard to move by hand.  And that's pretty much it!

 

-Tim.


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#132 KentTolley

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Posted 21 April 2019 - 12:28 PM

This is the mount that can rotate about the big bolt.  This single bolt does not hold the mount securely to the pier cap.

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Edited by KentTolley, 21 April 2019 - 02:08 PM.


#133 KentTolley

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Posted 21 April 2019 - 12:31 PM

This works much better.  Even here while taking a pic I checked and sure enough one of these set screws was loose.  

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#134 KentTolley

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Posted 21 April 2019 - 12:36 PM

BTW if those 3 screws on your mount were allen heads you would be able to tighten them with the big gear and clutch plates in place. I have only disassembled 3 Cave mounts but in each case these screws were allen heads.


Edited by KentTolley, 21 April 2019 - 12:37 PM.


#135 KentTolley

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Posted 21 April 2019 - 12:55 PM

(aside)  Thinking I may have a loose screw on my 10" I checked the bolt locking the pier cap to the mount and though it felt tight I was able to further tighten it with a socket wrench and that fixed it.

 

 

Still the two set screws are better than one big bolt with course threads.  When it's convenient I'll drill the pier cap for those 2 set screws. 

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Edited by KentTolley, 21 April 2019 - 01:06 PM.


#136 Guy Earle

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Posted 21 April 2019 - 09:47 PM

Those 3 screws attach the rear plate, as you call it, to the polar housing.  It is actually the cover to the clock housing  But loose you would get vibration in the mount.  To your 2nd question, yes.  Any loose screw is nfg.  Check them all.   

Thanks for the info, as I was concerned that another had fallen out at some point. I thought I had checked them all when I fixed the cord, but I missed those. Everything is happily snug now and it seems really good. I'm getting up again tomorrow morning for another test while the Moon and Jupiter are in a good part of the sky for me.


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#137 Guy Earle

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Posted 21 April 2019 - 09:49 PM

Since the back plate supports the worm block, there will be movement of the worm block and that could easily add up to quite a lot of slop in RA.  once you get these and other mounting srews snug, make sure the scope is well balanced, and adjust the clutch for the RA until you get just enough tighness to hold the scope in position but not so much that it's hard to move by hand.  And that's pretty much it!

 

-Tim.

Tim,

 

I've checked everything you've mentioned except for adjusting the clutch for the RA. How does one do that?

 

Guy



#138 KentTolley

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Posted 22 April 2019 - 06:59 AM

Tighten or loosen the 3 screws under the springs on the round clutch plate so you can move the scope in RA by hand but tight enough to hold the scope after you point it to an object.


Edited by KentTolley, 22 April 2019 - 07:54 AM.



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