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Another Cave 12.5" reporting aboard, with pictures

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#1 John Higbee

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Posted 17 September 2012 - 10:31 PM

Well, I took the plunge and can now cross something off my "bucket list" - owning an Astrola 12.5"!

Carol and I drove up to pick up the scope on 8 and 9 Sep (7.5 hour trip from the DC area). Rented a mini-van, which turned out to be an excellent idea...taking the Cave back in our Subaru Outback would have been an interesting (and difficult) proposition!

Carol's reaction on seeing the Cave was priceless...after 34 years together, my ability to surprise her has shrunk, but this did it (wide eyes, slack jaw, mouthing "OMG").

Aside from driving through some pretty rough weather in PA on the way back to DC (we cut obliquely through a 400 mile long squall line), the trip back was uneventful, and my son helped me unload and reassemble the model D in our garage.

First impressions (this scope was manufactured in 1979 - the last year of manufacture):

- Overall: great cosmetic condition (Sonotube is sound, with several small areas of missing paint
- Mount and pier; paint is good, with only small paint scrapes on several areas; both axes are bright with very minor rust
- Focuser: 2" rack and pinion with 1.25" adapter...no helical focusing feature. Marked "Japan".
- Mirrors: both the primary and secondary have bright coatings, with minor dust.
-- Primary: No label on the back. Primary is engraved with Cave Optical Company, focal length, and a 1979 date on the side (will be providing the specific info to the Cave Mirror registry shortly).
-- Secondary: One of the vanes for the secondary spider is not at a right angle to the adjacent vanes (off by 5 - 10 degrees...looks like it came this way from the factory.) Will drill the tube to reattach/straighten it out.
- 60mm guide scope: No name on the tube (looks a lot like my old Tasco 60mm). Has a .965 20mm Kellner eyepiece.
- Finder: 8X50 - works great - comes into sharp focus!
- Mount:
-- Declination Axis - Declination set screw is a MONSTER Allen set screw!
-- RA Axis - need to tighten the clutch - scope is "freewheeling" in RA.
-- Cradle - no "knurled disc nuts" on the two bolts coming off the rings - just wing nuts (went to two local hardware stores - a Home Depot and a "mom and pop" neighborhood shop...neither had them...so I'll be looking for replacements). Collar for the Decl quadrant slow motion on the axis (under the cradle) is held on by three machine bolts with "wing nut" heads, rather than allen head bolts.
- Drives:
-- Declination "slow motion": Motor works well in one direction; labors in the other. Hand paddle appears to work (need to check connections inside).
-- RA Drive: Looks like the drive baseplate (attached to the RA Axis support) is made of wood. No separate "power on" light - instead, the top of the toggle switch has a red "grain of wheat bulb" built in, which works. Drive motor is operational (watched it turn the large gear attached to the worm gear) Need to adjust the worm gear/RA axis gear alignment - it's slightly off.

So, I'm really excited to have it! Working on the above items is a lot easier with the good info the Forum provides on recent Cave maintenance. Once I finish up on those and collimate the optics, it'll be on to "first light"...wish me luck!

John

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#2 bob midiri

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Posted 17 September 2012 - 10:38 PM

Welcome to CN and an AWESOME find. Anxious to hear your first light reports. Congrats!! Bob

#3 tim53

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Posted 17 September 2012 - 10:54 PM

Very cool! Looking forward to seeing some pix.

Generally, if you keep them below 100K or so, you shouldn't have any problem attaching them.

-Tim.

#4 Da Bear

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Posted 17 September 2012 - 11:26 PM

Photo's please......

Da Bear

#5 John Higbee

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Posted 17 September 2012 - 11:37 PM

just broke the code - picture posted!

#6 JohnRW

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Posted 17 September 2012 - 11:38 PM

That is HUGE! Way to go! I suspect you'll need a ladder, right? I keep scrolling back up to grasp the sheer size in the photo you attached. Wow!

#7 John Higbee

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Posted 17 September 2012 - 11:51 PM

Thanks, John - here's one from the other side!

John

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#8 John Higbee

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Posted 18 September 2012 - 06:40 AM

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?

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#9 chuck52

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Posted 18 September 2012 - 07:09 AM

Beautiful Cave John, would love to see some more pictures!

#10 JohnRW

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Posted 18 September 2012 - 05:45 PM

I'd like to see more pictures too! Down the OTA? I'm going to have to inspect the clock drive on my own Cave a bit more closely to see how the gears are meshing.

#11 tim53

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Posted 18 September 2012 - 06:23 PM

Looks like the whole clutch/hub/gear assembly is mounted too far up the polar shaft to line up properly with the worm.

-Tim.

#12 John Higbee

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Posted 18 September 2012 - 06:51 PM

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

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#13 John Higbee

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Posted 18 September 2012 - 06:58 PM

Tim - agree...looks like the assembly needs to move around 1/2 inch down the shaft.
The three "bolts without springs" through the shaft drive gear assembly concern me more...all the drive pictures I've seen on the Forum so far show spring tensioners (my term for it) on each bolt. So, is this a late configuration, or a mistake?

#14 John Higbee

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Posted 18 September 2012 - 07:09 PM

Chuck - more pictures as requested! We'll start with the focuser/finder...(the left hand side of the tube looks distorted, but isn't - that's a combination of late afternoon light and a piece of white trim/gutter in the line of sight)

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#15 John Higbee

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Posted 18 September 2012 - 07:11 PM

...and a closeup of the mount...

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#16 Grava T

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Posted 18 September 2012 - 08:02 PM

Looks like the whole clutch/hub/gear assembly is mounted too far up the polar shaft to line up properly with the worm.

-Tim.


I agree with Tim.

You need to loosen the screws holding the worm assembly to the plate and move the RA gear further down the shaft. The screw holes for the worm gear should be a little oversized to allow some play for the gears to mesh.

Nice Cave scope BTW.

#17 PiSigma

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Posted 18 September 2012 - 08:19 PM

John, that one looks to be in excellent condition. Great find!

Tim's right, that clutch certainly looks like it needs to be slid down so that it is centered on the worm. Getting it right can be a bit tricky.

First, be sure you have the mount and OTA under control and balanced on both the dec and polar axes. Once you loosen the RA clutch the scope is going to be free to rotate around the RA axis.

I start by loosening the screw in the center of the drive motor and turning it so the small drive gear on the motor shaft disengages from the spur gear on the end of the worm gear shaft. Then loosen the screws through the top plate for the worm gear mount a little bit so that you can move the mount around. Then loosen the set screws that hold the RA shaft clutch to the shaft and center it on the worm.

Now slide the worm gear and mounting block around so that the mesh with the clutch gear isn't too tight, the worm gear shaft is parallel with the motor shaft, and that, when you go to turn the drive motor back, the spur gear and motor drive gear line up. It takes a few tries to get this right. When the mesh is just right I can spin the spur gear in both directions with my index finger and the mount and scope will move smoothly around the RA axis with very little backlash. Rotate the motor back up so those gears mesh and you should be good.

This assumes the clutch tension is not too loose. None of my Cave clutches have springs under those three clutch screws (I've only seen springs on my Criterion RV-6). They are socket head cap screws and, like yours, have split washers under them (although only one on each of mine). Mine do not have nuts on top, the upper hub is tapped for the screws. But mine are all 8" and 10" Caves so maybe the 12.5" are different there. The tension is controlled by a teflon(?) band inside the clutch. Most of my clutch screws are snug but not tight. There is a point where just a small additional turn on the screws makes a big difference in the clutch tension and this is when it is really starting to 'squash' the teflon band.

I've not seen a Cave with a drive cover seal like yours. It looks like felt around the edge of the top plate.

Your tube end rings are also different than later Caves I've seen. Rather than being the cast aluminum pull off rings they appear to be L shaped bands with a split and little screws.

I would love pictures of the mirror engraving for the Registry. Maybe yours is later than the latest one known?

Here is a shot of one of my RA clutches. The clutch at the upper left with the big center hole is my dec. drive clutch.

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#18 John Higbee

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Posted 18 September 2012 - 08:42 PM

Thanks, Mike!

#19 Datapanic

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Posted 18 September 2012 - 08:52 PM

The older Cave's with the steel front and rear plates may have had springs - at least that's what I found when I started rebuilding the Horsetrail Cave. I think springs give a little bit finer adjustment than split washers.

While you're adjusting all the clock drive, there's also a lateral adjustment on the worm gear itself with two bolts with their heads overlapping those brass bushings. The main adjustment there is to not have any motion along the shaft the worm gear is on.

Overall - looks really nice and well taken care of - congratulations!

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#20 John Higbee

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Posted 18 September 2012 - 08:53 PM

Jon - Thanks for the detailed instructions on realigning the drive, and the exploded views of the drive gear/clutch assembly. It's exactly what I needed to do that job correctly.
You'll have the detailed data on my mirror this weekend. I plan to dismount the primary and secondary mirrors so I can give the inside of the OTA a good dusting/cleaning...so I'll take pictures of the primary and send them to you then.
The drive plate cover is not metal...looks to me to be wood, painted to match the rest of the mount (the surface of the plate has a wood texture through the paint). It does have a felt "gasket" around the edge of the plate. Could be another "late production anomaly"!

#21 John Higbee

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Posted 18 September 2012 - 09:23 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

#22 tim53

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Posted 18 September 2012 - 09:30 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

#23 CHASLX200

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Posted 19 September 2012 - 05:09 AM

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

#24 Calypte

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Posted 19 September 2012 - 06:34 PM

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.

#25 Calypte

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Posted 19 September 2012 - 06:37 PM

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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