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Equipment Discussions >> Classic Telescopes

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John Higbee
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Reged: 07/17/12

Loc: Virginia
Re: Another Cave 12.5" reporting aboard! new [Re: Datapanic]
      #5428397 - 09/18/12 10:23 PM

Dan - thanks! I feel lucky and very fortunate to have gotten this scope...and owe a big "thank you" to Stan Lopata and his wife Terry for making it possible for me to own it (we had a nice visit with them when we drove up to pick up the scope).
Different topic - I can rotate the OTA within the rings, but it takes some effort to do so...is there anything I should check that might make the rotation easier?

John


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tim53
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Reged: 12/17/04

Loc: Highland Park, CA
Re: Another Cave 12.5" reporting aboard! new [Re: John Higbee]
      #5428407 - 09/18/12 10:30 PM

As Meade was actively putting cave out of business, I heard all kinds of stories of ways cave got scopes completed after his suppliers stopped supplying things like fiberglass tubes and such. All the late caves seem to have Meade focusers and finders on them, though Meade only labeled Japanese imports themselves. I hope that drive wasn't assembled that way at cave, but it might have been!

Tim


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CHASLX200
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Reged: 09/29/07

Loc: Tampa area Florida
Re: Another Cave 12.5" reporting aboard! new [Re: John Higbee]
      #5428761 - 09/19/12 06:09 AM

Quote:

Dan - thanks! I feel lucky and very fortunate to have gotten this scope...and owe a big "thank you" to Stan Lopata and his wife Terry for making it possible for me to own it (we had a nice visit with them when we drove up to pick up the scope).
Different topic - I can rotate the OTA within the rings, but it takes some effort to do so...is there anything I should check that might make the rotation easier?

John




I would check all the hex heads on the outer rings and make sure they are not too tight.

Chas


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Calypte
Pooh-Bah


Reged: 03/20/07

Loc: Anza, California
Re: Another Cave 12.5" reporting aboard! new [Re: John Higbee]
      #5429774 - 09/19/12 07:34 PM

Quote:

And a picture of the drive with the case off...note that the RA axis gear and the drive worm are hardly engaged, and that the adjustment bolts with springs that I've seen in every other Cave drive aren't present here...the three bolts have what look like two split collar washers, and a nut on the other side...with everything "tightened up". Any thoughts on that?



I don't have an answer to your question, but I do notice something about your RA drive. In 1993 I bought a consignment Cave 12.5-inch f/5 with the lighter mount, like yours. Almost in the center of your picture is a brass thrust bearing for the worm, and it's held in place by the lip of a small round-head Allyn screw. As you move the scope around in RA, the entire mass of the scope pushes on the tiny contact of that screw and thrust bearing. On my scope, the force of moving the scope would rip the screw head right through the flange of the thrust bearing. I found a local hardware store that stocked those thrust bearings, and I went through a boatload of them. Eventually I replaced the drive with a Byers 9-inch drive. The mount is still too small for the scope, but the Byers drive turned a nightmare into something usable.


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Calypte
Pooh-Bah


Reged: 03/20/07

Loc: Anza, California
Re: Another Cave 12.5" reporting aboard! new [Re: John Higbee]
      #5429779 - 09/19/12 07:37 PM

Quote:

John - here's the "down the OTA" shot!



On mine (my scope was made in 1978), the spider was way too light. The diagonal would sag as the scope was moved, making accurate collimation impossible. I replaced the spider with a Novak spider, which is orders of magnitude more rigid than the original.


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John Higbee
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Reged: 07/17/12

Loc: Virginia
Re: Another Cave 12.5" reporting aboard! new [Re: Calypte]
      #5429844 - 09/19/12 08:20 PM

Calypte - thanks for the information and advice on the drive and the spider...if repositioning the "crooked leg" of the spider to a right angle position dosn't give me the necessary stiffness, I'll be looking for a replacement quickly. As for the drive, I'll be on the lookout for the behavior you experienced once I get it realigned and operating. John

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John Higbee
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Reged: 07/17/12

Loc: Virginia
Re: Another Cave 12.5" reporting aboard! new [Re: CHASLX200]
      #5429937 - 09/19/12 09:15 PM

Chas - took your advice - backed all eight hex heads in the outer rings out 1/2 turn, and the tube spins smoothly! Thanks, John

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CHASLX200
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Reged: 09/29/07

Loc: Tampa area Florida
Re: Another Cave 12.5" reporting aboard! new [Re: John Higbee]
      #5430395 - 09/20/12 06:15 AM

Glad that helped.

Chas


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John Higbee
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Reged: 07/17/12

Loc: Virginia
Re: Another Cave 12.5" reporting aboard! new [Re: PiSigma]
      #5434332 - 09/22/12 12:12 PM

It's Saturday, and I've begun taking the primary and secondary mirrors out of the OTA (so, Jon, should have the data for the registry soon).

Once that's done, I'll begin realigning the drive.

If I need to clean the mirrors while they're out (and I won't do it unless they're a lot dirtier than they look), what would you recommend as the best way to clean the primary?

John


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amicus sidera
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Reged: 10/14/11

Loc: East of the Sun, West of the M...
Re: Another Cave 12.5" reporting aboard! new [Re: John Higbee]
      #5434788 - 09/22/12 05:20 PM

Quote:


If I need to clean the mirrors while they're out (and I won't do it unless they're a lot dirtier than they look), what would you recommend as the best way to clean the primary?






FWIW, this page from P. Clay Sherrod's Arkansas Sky Observatory website might prove of interest to you: The Cleaning of Optical surfaces: Mirrors...YMMV.



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John Higbee
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Reged: 07/17/12

Loc: Virginia
Re: Another Cave 12.5" reporting aboard! new [Re: amicus sidera]
      #5435045 - 09/22/12 08:27 PM

thanks, Fred! John

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John Higbee
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Reged: 07/17/12

Loc: Virginia
Re: Another Cave 12.5" reporting aboard! new [Re: tim53]
      #5435917 - 09/23/12 11:22 AM

Well - I've begun my effort to realign the drive, and now things are getting interesting.
Tim - Per your comment, I think the condition of the drive IS as it was assembled at Cave; the gears all look pristine (no wear on any of the gear surfaces).
I dismounted the worm gear assembly to get more room for working on the clutch/axis drive gear assembly. The clutch/drive assembly was held on by 1 allen head set screw in the upper plate hub...is that the normal configuration?
After taking the set screw out, I was able to work the assembly off the polar axis. I took out the three machine bolts (each with two lock washers and a nut). Jon - turns out that the machine bolts were undersized..the upper plate was indeed tapped for a larger machine bolt. I've replaced the original hardware with three stainless steel cap head machine bolts of the right size, with a stainless steel lock washer and regular washer installed on each. So far, so good...
I took out the new hardware, so I could separate the three parts of the assembly...and so far, haven't been able to get them apart to check the teflon ring (remember that the original bolt/nut hardware was found "tightened up").
So - two questions:
- how can I get the three disks apart without damaging the axis drive gear?
- If I find the teflon ring trashed (or not there), what thickness/type of teflon should I use to repair it?

thanks, John


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Datapanic
Carpal Tunnel
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Reged: 10/17/09

Loc: Tucson, Arizona
Re: Another Cave 12.5" reporting aboard! new [Re: John Higbee]
      #5435982 - 09/23/12 12:01 PM

Soak the whole thing in warm soapy water for a while - the grease has probably dried up and it just needs to be worked loose.

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John Higbee
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Reged: 07/17/12

Loc: Virginia
Re: Another Cave 12.5" reporting aboard! new [Re: Datapanic]
      #5436339 - 09/23/12 03:11 PM

Dan - your suggestion worked like a champ...all three components are apart...congealed brown grease (very sticky - more like an adhesive than a lubricant) on all the edges. First step now is to get that stuff off...once it's off, what sort of gear lube do you use to replace it?
The teflon strip is intact, but seems very thin...would you reuse it, or replace it? If replace it, who sells teflon sheets?

thanks for the help, John


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Datapanic
Carpal Tunnel
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Reged: 10/17/09

Loc: Tucson, Arizona
Re: Another Cave 12.5" reporting aboard! new [Re: John Higbee]
      #5436445 - 09/23/12 04:04 PM

I would first clean up the teflon strip with some dish soap and reuse it - it should be okay.

For lube, I've gone with "Super Lube" brand Synthetic Grease "With Syncolon" over petroleum based lubes and it seems to work just fine. It has a wide temperature range and doesn't start dripping off the gears and making a mess during hot weather.

Once the teflon strip is cleaned up, coat it as well as the ring gear and the area where it rotates on the front and back of the assembly.


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John Higbee
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Reged: 07/17/12

Loc: Virginia
Re: Another Cave 12.5" reporting aboard! new [Re: PiSigma]
      #5437116 - 09/23/12 10:35 PM

Jon - just got the mirror data (with the help of my son...that mirror cell is heavy)...
Cave Optical Co
M793839
F/6 75 1/8 F.L.
Mar 27 1979

Picture will follow tomorrow once my son sends it off his phone.

John


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John Higbee
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Reged: 07/17/12

Loc: Virginia
Re: Another Cave 12.5" reporting aboard! new [Re: Datapanic]
      #5438593 - 09/24/12 06:26 PM

Dan - thanks - lube both sides of the teflon strip, or just the side in contact with the inner hub of the ring gear? (sorry for the stupid questions...just want to get it right).
John


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Datapanic
Carpal Tunnel
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Reged: 10/17/09

Loc: Tucson, Arizona
Re: Another Cave 12.5" reporting aboard! new [Re: John Higbee]
      #5438603 - 09/24/12 06:35 PM

Both sides - just a thin coat by putting a dab on your fingers and pulling the strip between them.

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John Higbee
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Reged: 07/17/12

Loc: Virginia
Re: Another Cave 12.5" reporting aboard! new [Re: John Higbee]
      #5438914 - 09/24/12 10:50 PM Attachment (15 downloads)

...and here's the mirror engraving...John

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John Higbee
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Reged: 07/17/12

Loc: Virginia
Re: Another Cave 12.5" reporting aboard! new [Re: John Higbee]
      #5516438 - 11/12/12 06:14 PM Attachment (13 downloads)

Well, it's been a while since the last post (what with work and Superstorm Sandy), but I've made steady progress on my Cave 12.5 in the interim. Thought I'd provide some pictures of what's been done, as well as one of my latest challenge. So, here goes:

First, I've realigned and overhauled the drive. If you compare this drive picture with the one I took early on, you'll see that I've aligned the drive gear/clutch assembly with the worm gear, after taking that assembly apart, cleaning it and relubing it with lithium grease (many thanks to Jon (PiSigma) and Dan (Datapanic) for walking me though the process). When I reassembled the drive gear/clutch, I got rid of the "funky" undersized machine bolts and nuts, and substituted the original design cap head machine bolts with lock washers (stainless steel)...they fit perfectly in the existing threads machined into the "upstream" disk.
On the test run, everything ran well...the Synchron motor was smooth and almost silent throughout. The tube now holds position in RA...no more "freewheeling".

I'm pretty sure now that the "as received" condition of the drive was the way the drive left the Cave shop in 1979, as Tim theorized earlier.

Edited by John Higbee (11/12/12 06:16 PM)


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