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'59 Cave mount question

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#1 Guy Earle

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Posted 28 June 2020 - 09:40 PM

Evening, all:

 

About a year ago I posted my first imaging pics of the '59 Cave Astrola 10" f/7.1 that I restored, and I have a question regarding the mount itself, please. The OTA is 52.8 lbs and the counterweight 34.8 lbs. Can the 1.5" shaft of this old beefy beast handle an additional 30 lbs of OTA and 20 lbs of counterweight? I know the 12.5" Cave has larger shafts, but this thing is so seemingly overbuilt I'm wondering what are the weight limits.

 

Thanks,

 

Guy



#2 CHASLX200

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Posted 29 June 2020 - 06:10 AM

I don't see how it could. Last 1.5" Cave mount i had was so bad that any touch of the 10" F/6 OTA sent it shaking for 8 secs after the touch. There was something wrong with that mount.  Seems the 10" size is the max for the 1.5" mounts. But Cave did sell the 12.5" on the same mount. 



#3 Jeff B

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Posted 29 June 2020 - 12:29 PM

Guy, my experience is similar to Chas's. 

 

I've owned or had direct, hands on experiences with all of the Cave mounts, at least a dozen of them, by either direct ownership or those that came in our store (Astronomy New England), used, in the early, mid 80's as trades-ins or for consignment sale..  And the 10" scope is really about the max I would go with the 1.5" shafted mounts. 

 

It's not the shafts that introduce that vibrations, it's the combined flexures in the castings (RA, DEC and saddle), top cap-to-RA joint, legs to pier joint along with the necessary slop in the rotating rings and, especially, the worm to wheel fit and clutch adjustments.  And then there are those casters, great for moving the scope, terrible for observing.  Each area of flexure requires attention.  For example, eye bolt/turnbuckle arrangement between the bottom of the motor box casting and the pier wall as well as between the leg tips and pier wall and even the arms of the saddle.  Then, very careful adjustments to the rotating rings and drive system, especially the clutch pre-loading of worm/wheel assembly.  If you address each of these areas, you can extend the payload and moment arm range a bit to allow for focusing at high power.  However, unless you have the bigger drive gear associated with the bigger "transportable" series scopes, I bet the stock drive system will bee your "pinch point".

 

Jeff



#4 icomet

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Posted 29 June 2020 - 05:59 PM

I just recently put this together.

10" f/7.5 

84" tube

Cave rings, and all of the other stuff, with a 3-fan bank for the primary/tube currents.

 

It sits on a 1981 Meade DS-16 mount, that I took the 16" f/4.5 scope off of.

Here's an image of it to compare sizes. This mount has 1.5" shaft, and the pier, etc.

is very light, well compared to my 12.5" model "D", it's like, weightless. 

 

I haven't had a chance to set it up outside yet. It's next on my list, after it quits raining. 

In the image it has all the counter weights on it. That was for the "press release photos".

I only need the 40# wt. on it, all the way to the top.

 

I'm sure that these mounts might be comparable. Not seeing a 1.5" Cave mount

before, I'd think that the Cave would be heavier, per my Cave mount which is 2" shaft and

not 2.5".

 

It had that 16" scope on it, and a 19" diameter, 1/2" thick, or so, sonotube.

Hope by seeing this, it might help you out.

 

Clear Skies.

Attached Thumbnails

  • tube mounted sm.jpg

  • tim53, Mr Magoo, Jeff B and 5 others like this

#5 Jeff B

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Posted 29 June 2020 - 09:21 PM

Nice!  I love the F7.5 focal ratio for newts.  What's that under cover in the background?



#6 bjkaras

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Posted 01 July 2020 - 04:11 PM

I just recently put this together.

10" f/7.5 

84" tube

Cave rings, and all of the other stuff, with a 3-fan bank for the primary/tube currents.

 

It sits on a 1981 Meade DS-16 mount, that I took the 16" f/4.5 scope off of.

Here's an image of it to compare sizes. This mount has 1.5" shaft, and the pier, etc.

is very light, well compared to my 12.5" model "D", it's like, weightless. 

 

I haven't had a chance to set it up outside yet. It's next on my list, after it quits raining. 

In the image it has all the counter weights on it. That was for the "press release photos".

I only need the 40# wt. on it, all the way to the top.

 

I'm sure that these mounts might be comparable. Not seeing a 1.5" Cave mount

before, I'd think that the Cave would be heavier, per my Cave mount which is 2" shaft and

not 2.5".

 

It had that 16" scope on it, and a 19" diameter, 1/2" thick, or so, sonotube.

Hope by seeing this, it might help you out.

 

Clear Skies.

I have the Parks 1.5” shaft mount for my 10”. It’s basically a clone of the old Cave mount, but I think the Parks mount is quite a bit heavier. Completely assembled, with the 10” OTA attached, it’s around 230 lbs. I love those Parks tubes though. Too bad you can’t get them any more.



#7 icomet

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Posted 01 July 2020 - 08:19 PM

Nice!  I love the F7.5 focal ratio for newts.  What's that under cover in the background?

12.5" f/7 Cave Astrola model D, 1950's circa.  (Have letter stating it was purchased before 1960. It was

replacing a 9" Braesher Refractor)

 

No mirror markings. The rings weren't designed well; unable to adjust tension properly, so I 

machined/corrected that, along with dec shaft/cradle bolt put in, rewired the whole system with

upgrades, and quick adjusters for the clutch. Also, the original mirror cell is now mo' betta.


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#8 Jeff B

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Posted Today, 09:48 AM

12.5" f/7 Cave Astrola model D, 1950's circa.  (Have letter stating it was purchased before 1960. It was

replacing a 9" Braesher Refractor)

 

No mirror markings. The rings weren't designed well; unable to adjust tension properly, so I 

machined/corrected that, along with dec shaft/cradle bolt put in, rewired the whole system with

upgrades, and quick adjusters for the clutch. Also, the original mirror cell is now mo' betta.

Yes! waytogo.gif

 

I had forgotten about that single bolt through the top of the saddle that holds it in place on the end of the Dec shaft.  One more source of wobble and flex.

 

So, let's see some pictures of the 12.5"?

 

Jeff



#9 icomet

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Posted Today, 01:24 PM

Yes! waytogo.gif

 

I had forgotten about that single bolt through the top of the saddle that holds it in place on the end of the Dec shaft.  One more source of wobble and flex.

 

So, let's see some pictures of the 12.5"?

 

Jeff

I sent a PM. Did you get it?

Attached Thumbnails

  • Cave Astrola 1sm.jpg

Edited by icomet, Today, 02:28 PM.



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