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12.5" F6 Cave

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#51 65&Counting

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Posted 23 June 2019 - 10:14 AM

I'm definitely 'old school' but that was always a huge part of the fun of it all. Just like restoring this scope.

 

One of the guys with the astronomy club where I picked up the scope has his own observatory/dome, paramount drive with super-scope, automated everything, and can sit in his house and run all of it on computer - astrophotography - everything. Plop down $50,000+ and you can have everything - and it doesn't appeal to me.

 

I mean - the hobby isn't intended to be a computer toy - is it? Another video game? If so I'm not so interested. I get the appeal - it's just not for me

 

I used to build my own go-carts - now you can plop down $500-1000 and buy one - which is more fun? I got more thrill getting an ancient Briggs washing machine engine running and the cart moving on its own. I guess it's either in your soul or it ain't.


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#52 65&Counting

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Posted 27 June 2019 - 12:36 PM

Another question for the experts,

 

How does a Cave mount wire up without a Dec drive? Just curious.

 

Why is there a resistor soldered into the light on the 12.5?

 

Electrical is my downfall :-(

 

But I'm trying to learn - I can copy stuff but looking at an electrical diagram is like hieroglyphics.



#53 starman876

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Posted 27 June 2019 - 03:33 PM

Another question for the experts,

 

How does a Cave mount wire up without a Dec drive? Just curious.

 

Why is there a resistor soldered into the light on the 12.5?

 

Electrical is my downfall :-(

 

But I'm trying to learn - I can copy stuff but looking at an electrical diagram is like hieroglyphics.

The resistor is there to limit the current and most likely the voltage to the bulb.   


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#54 65&Counting

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Posted 27 June 2019 - 03:44 PM

I felt the Cave mount had some issues so I put mine on a Parks Superior mount with 6.6" OpticCraft drive. Much more stable on the Parks. With a Mototrak V drive corrector I tried a little autoguiding with PHD and it did fine.

Rolo - what focuser do you have on your 12.5" F6" - I'm looking for one and want both functional and 'original' form fitting tube look - thanks.



#55 PiSigma

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Posted 28 June 2019 - 06:52 PM

Another question for the experts,

 

How does a Cave mount wire up without a Dec drive? Just curious.

 

Why is there a resistor soldered into the light on the 12.5?

 

Electrical is my downfall :-(

 

But I'm trying to learn - I can copy stuff but looking at an electrical diagram is like hieroglyphics.

The Dec and RA are actually wired completely separate. Here is a diagram that has been floating around the interwebs for a while. My 1971 10" f/6 Custom Super Deluxe is wired exactly the same except for the ground shown on the RA diagram.

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#56 John Higbee

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Posted 29 June 2019 - 05:29 AM

Rolo - what focuser do you have on your 12.5" F6" - I'm looking for one and want both functional and 'original' form fitting tube look - thanks.

Thought I'd chime in, since I have a 1979 vintage 12.5" f/6...

 

Mine came with a Meade rack and pinion focuser (accommodates 2" eyepieces, and 1 1/4" eyepieces with an adapter).  It's sturdy and serviceable.

 

I also have a Sky Micro Giant (2") focuser, which is a step up from the Meade in its construction...it's a rack and pinion focuser which also provides fine focusing via helical adjustment.  To the best of my knowledge, these were not stock on Caves...they were upgrades from a separate vendor.  I plan to install this the next time I maintain the scope.

 

They haven't been made for decades, but will (very infrequently) show up for sale in Astromart / Cloudy Nights.  They usually disappear within hours of posting.

 

If maintaining the '70s configuration is not a priority, there are many good choices for current focusers that you can retrofit.


Edited by John Higbee, 29 June 2019 - 05:52 AM.

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#57 tim53

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Posted 29 June 2019 - 09:23 AM

Sky Micro focusers were an accessory upgrade in the Cave catalogs.


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#58 65&Counting

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Posted 29 June 2019 - 03:27 PM

Thanks for all the help from everyone.

 

I really like the 'form fitting' wrap around the tube type style focuser base that I always remembered seeing in the Cave pix - and also thinking this will help keep dust out - I do have a Meade style 2" that fits but don't like the exposed gap on the sides.

 

Most vendors don't really say what tube O.D. is optimal but just give a range. The ability to handle some weight would be nice but not necessary. ScopeStuff and others have some options & I see some Chinese venders on eBay - decisions decisions. That Sky Micro Giant looks neat John - I also love your Cave restoration story and has been an inspiration!

 

Speaking of vendors I talked to a super-nice helpful (youngster) at High Point Scientific about proper tube size AstroZap dust covers & the 14" RC fit perfectly - I'm really surprised that vendors list almost no useful info as to dimensions of things (like screws & misc parts) on-line or whether they're talking about mirror sizes or tube O.D. sizes. It's like everything is marketed for one commercial product only when things might have multiple uses. High Point won a customer!

 

About the wiring - my 12.5 came with the R.A. and Dec wired to one plug with the toggle switch for R.A. - appreciate the diagram with them split and explains a lot. Ordered G.E. NE-51 spare neon bulbs with resistors - had no idea these were neon! Project just keeps getting better. Am a bit confused about what resistor is best though - the diagram says 115k ohm but an original G.E. manual I found says 220k ohm for the NE-51 - I guess the latter will be dimmer but last longer?



#59 ltha

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Posted 01 July 2019 - 11:27 PM

I have a Cave 12 3/4” custom made for Dr Henry Paul who published several books on telescopes and astronomy. The primary is quartz and was tested by the head optician at Mt Palomar before it went to Dr. Paul. Tested a few years ago by one of the finest mirror makers in the US who pronounced it an excellent mirror. Mine is mounted on a Schaefer which carries it quite easily. 

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#60 ltha

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Posted 01 July 2019 - 11:33 PM

My friend and mentor Larry Myers, who formerly owned Mountain Instruments and made MI-250 mounts, helping me dial it in.  

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#61 ltha

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Posted 01 July 2019 - 11:48 PM

I put a dual speed Moonlite on mine. The adapter fit the tube almost perfectly. Not OEM but incredibly functional. 

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Edited by ltha, 01 July 2019 - 11:50 PM.

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#62 John Higbee

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Posted 02 July 2019 - 02:11 AM

I have a Cave 12 3/4” custom made for Dr Henry Paul who published several books on telescopes and astronomy. The primary is quartz and was tested by the head optician at Mt Palomar before it went to Dr. Paul. Tested a few years ago by one of the finest mirror makers in the US who pronounced it an excellent mirror. Mine is mounted on a Schaefer which carries it quite easily. 

what a beautiful telescope!



#63 65&Counting

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Posted 02 July 2019 - 11:53 AM

I put a dual speed Moonlite on mine. The adapter fit the tube almost perfectly. Not OEM but incredibly functional. 

Ahhhhh - that looks nice - is the low profile ever an issue and can extender tubes be purchased for these?

 

The one I have (also the one on my Star-Liner DeLuxe) seems to have around 4 inches of travel or so.

 

Don't want to redrill any new holes in the beautiful fiberglass tube!



#64 65&Counting

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Posted 02 July 2019 - 12:09 PM

Here's a question for the older Cave folks (and really about any older style newtonian 'T' mount out of date).

 

I've always wondered why the weakest part of the equatorial mount seemed to be the basic design of relying on larger shafts (more weight) for stability of large size OTA when the entire design could have been fairly easily reconsidered.

 

The answer always seemed simple (to me) and is the way Byers, Astro-Physics, Paramount, etc. etc. do it - like the way Dr. Henry Paul's mount is made. Just weld the larger round mating plate onto the Dec casting and meet the like-minded on R.A. where all the weight is really carried - not unlike an 'upgrade' to some Byers Drive but instead of hanging way off the end of the R.A. casting - do this design - seems simple and much more stable.... and, kinda obvious? Perfect place for the R.A. drive motor/gear also.

 

What wasn't this the standard way to do things? A large facing thrust bearing at the junction of the R.A. & Dec and you've got gobs of stability? Even Astro-Physics mounts have a smaller screw on shaft for weights/balancing which is obviously essential no matter what - but isn't an integral part of the mount's overall stability?

 

Just curious after seeing this on his seemingly modified older-style mount.


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#65 tim53

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Posted 02 July 2019 - 03:00 PM

Here's a question for the older Cave folks (and really about any older style newtonian 'T' mount out of date).

 

I've always wondered why the weakest part of the equatorial mount seemed to be the basic design of relying on larger shafts (more weight) for stability of large size OTA when the entire design could have been fairly easily reconsidered.

 

The answer always seemed simple (to me) and is the way Byers, Astro-Physics, Paramount, etc. etc. do it - like the way Dr. Henry Paul's mount is made. Just weld the larger round mating plate onto the Dec casting and meet the like-minded on R.A. where all the weight is really carried - not unlike an 'upgrade' to some Byers Drive but instead of hanging way off the end of the R.A. casting - do this design - seems simple and much more stable.... and, kinda obvious? Perfect place for the R.A. drive motor/gear also.

 

What wasn't this the standard way to do things? A large facing thrust bearing at the junction of the R.A. & Dec and you've got gobs of stability? Even Astro-Physics mounts have a smaller screw on shaft for weights/balancing which is obviously essential no matter what - but isn't an integral part of the mount's overall stability?

 

Just curious after seeing this on his seemingly modified older-style mount.

That idea dates back at least to the late 19th century, and is commonly depicted in Russell Porter's drawings in the ATM articles in Scientific American during the 20s and 30s.  Tom's mount was designed by Bill Schaefer beginning in the 50s and extending throughout his life into the early 90s.  Of the commercial mount makers of the 60s, I would point to Optical Craftsmen.  Though they also used long heavy steel shafts and put the RA drive at the south end of the polar axis like most other manufacturers did from Cave on through Star Liner, OC had moderately large thrust surfaces at the junctures of the RA and Dec axes that really help with stability.

 

More modern mounts use short, hollow shafts, which is better still.


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#66 ltha

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Posted 02 July 2019 - 05:35 PM

Ahhhhh - that looks nice - is the low profile ever an issue and can extender tubes be purchased for these?

 

The one I have (also the one on my Star-Liner DeLuxe) seems to have around 4 inches of travel or so.

 

Don't want to redrill any new holes in the beautiful fiberglass tube!

The kit that came with my Moonlite included several spacers in addition to two radiused blocks. One block was nearly a perfect match for the old Cave tube. Between the block and spacers I was able to easily match the height of the old school 2” focuser the scope came with. I decided to leave it a tad shorter and use a 2” extension as needed which allowed an even wider range of eyepieces to reach focus. Interestingly, Dr Paul specified the 1.25” Sky-micro focuser. The 2” was added after the scope left Dr Paul. Since it was not original, I was not bothered by going to the newer Moonlite.

 

 Rolo owned the scope before me and gave me a glowing report about its performance. Knowing him as well as I do, particularly his ability to judge optical performance, I was expecting a real winner. One night I had it out side-by-side with my TEC200ED in very good+ seeing. The Cave was definitely better on the planets and nebulae. The TEC is a superb scope and matches seeing more often than the big Cave. Plus, you can observe seated and easily switch to a binoviewer. But if the seeing is there the Cave is amazing. Looking at M42 in both I could not believe the 3-D luminescence through the Cave. It was so amazing I forgot I was two steps up and took an unexpectedly long step back to the ground.....


Edited by ltha, 02 July 2019 - 05:36 PM.

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#67 bjkaras

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Posted 08 July 2019 - 01:37 AM

I have a 10" f/5 Parks, but I think it's the same as

the 1.5" Astrola mounting. It's the equivalent of the

Model C Astrola. It takes about two seconds  

to damp out. At f/5 the tube is short enough that

it has a low moment of inertia so it doesn't put too

much stain on the mount, but there is some wobble while 

the vibrations damp out. It's easier to handle than 

the 12.5", d I don't have to struggle too much, but 

it's about the largest scope that one person can handle

easily. I'm really happy to have those casters! 


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#68 bjkaras

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Posted 10 July 2019 - 01:54 PM

Rolo, I have a similar setup for my 10" f/5. The Parks Superior mount handles it fairly well, but I want to upgrade the drive system. How do you like the Opticcraft drive? I'm looking at one of this since Ed Byers is retiring and isn't making any more drives. Can you give me some input into your drive? Do you also have a dec drive from them? How do you control it? My dec motor needs to be rewired, but instead I think I'll just replace the whole drive system. Since no one seems to make synchronous drives any more, I'm interested in what you think of yours.

 

Brian


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#69 dhferguson

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Posted 14 July 2019 - 12:39 PM

Hello Brian,

 

You may want to have a look at my post on installing Byers drives on my 1.5" Astrola mount for ideas. My understanding is that OptiCraft Machining drives are quite decent.

 

You have three choices as to motors:

(1) synchronous AC motors: reliable, easy to wire, but may require an AC drive corrector if you want to do astro-imaging. There is one company in the UK that still makes drive correctors but maybe it's best just to buy used on CN or AM--they come up periodically. Typically, for a 9" drive, the gear will have either 359 (pure sidereal rate) or 360 (nice interface w/Losmandy stepper controller, see (2), below). BTW, this is the solution I chose due to parts availability: those AC Hurst motors (see their website) have been available for decades,

 

(2) DC stepper motors: many prefer this solution. A stepper motor and controller board are required for each axis. Various options exist for controller boards. Some use the Losmandy controllers. Others buy this-or-that controller and optimize it for their system (requires a bit of electronics knowledge). This solution will also allow you to make your scope "goto", BTW,

 

(3) servo motors: this is the Cadillac solution and often used in much larger mounts. SciTech sells controllers and motors. However, I am concerned that, when eventually SciTech disappears (this is, after all, a hobby industry with few semi-permanent vendors), so too will availability of boards/ICs, etc.

 

BTW, the old Hurst motor wiring on my old (pre-Byers) Dec drive also became frayed and dangerous, and I had to replace the motor some years ago. These particular Hurst motors are rather expensive.

 

Regarding controlling the drives, given that I used AC synchronous motors, the wiring was similar to the Cave diagram someone posted above. I also wired in a hand controller for really smooth slow motion control.

 

Happy observing always,

 

Don


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#70 photoracer18

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Posted 19 July 2019 - 02:45 PM

Thought I'd chime in, since I have a 1979 vintage 12.5" f/6...

 

Mine came with a Meade rack and pinion focuser (accommodates 2" eyepieces, and 1 1/4" eyepieces with an adapter).  It's sturdy and serviceable.

 

I also have a Sky Micro Giant (2") focuser, which is a step up from the Meade in its construction...it's a rack and pinion focuser which also provides fine focusing via helical adjustment.  To the best of my knowledge, these were not stock on Caves...they were upgrades from a separate vendor.  I plan to install this the next time I maintain the scope.

 

They haven't been made for decades, but will (very infrequently) show up for sale in Astromart / Cloudy Nights.  They usually disappear within hours of posting.

 

If maintaining the '70s configuration is not a priority, there are many good choices for current focusers that you can retrofit.

I don't see a startup capacitor on the RA drive on that diagram? Does the Bristol motor have one internally? All Synchronous AC motors have to have one and which leads you put it on determines which direction it turns (all Hurst motors came with the capacitor). That is how the Schaefer mounts work with dual motors, on both ends of the worm shaft, with the caps across alternate leads. My Cave early 60's 12.5" Convertible Cass/Newt came with Sky Micro Giants on both positions, although I don't know if they are original (I suspect so) since the original Cave primary was swapped out for one from Optical Craftsman in around the late 60's.


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#71 photoracer18

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Posted 19 July 2019 - 03:12 PM

A lot of makers used AC synchronous motors on both RA and DEC axis (Cave and Schaefer certainly did). As far as I know the only commercial drive controllers available that way were made by Vista. 95% of all the other controllers on the market were designed instead for DC motors on the DEC axis so they could be used on later mounts, including Celestron and Meade SCTs and Meade GEMs, the later because they all drove the tangent arm DEC with small DC motors (bigger market). This includes drive controllers from Orion/Geiseller (Accutrack) and Vogel (Digitraks). All the others sold were usually rebadged from those 2, including Lumicon and others. A tangent arm DEC does not require a very large motor to run properly. My mount collection includes a custom remodeled Meade DS-16 with a Byers 11.3" driven by a large geared stepper in RA and the DEC driving the same little tiny DC motor that came with the Meade mount originally, all controlled by a Byers controller w/hand-paddle.

My Schaefer AT-9 has AC on both axis and finding an all AC controller has not been possible (previous owners have just driven the RA with a single axis controller) At this time I am planning to rewire it to DC on the DEC as I have a couple of AC/DC controllers from each vendor. I could likely just drive it with the motor from a Celestron or JMI DEC kit, but I want to use a motor with more torque.



#72 erbyers

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Posted 22 July 2019 - 09:20 AM

I certainly will be retiring, however I still have several drives left in my inventory after over 67 years in the business.

 

Ed Byers

 

 

Rolo, I have a similar setup for my 10" f/5. The Parks Superior mount handles it fairly well, but I want to upgrade the drive system. How do you like the Opticcraft drive? I'm looking at one of this since Ed Byers is retiring and isn't making any more drives. Can you give me some input into your drive? Do you also have a dec drive from them? How do you control it? My dec motor needs to be rewired, but instead I think I'll just replace the whole drive system. Since no one seems to make synchronous drives any more, I'm interested in what you think of yours.

 

Brian


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#73 65&Counting

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Posted 22 July 2019 - 11:18 AM

Another question regarding the 1 rpm Bristol motor on stock Cave drives - it seems a bit 'puny' with a long shaft and the spur gear on the end.

 

I know Byers or some such is the ultimate way to go but would a 1 rpm Hurst (they're larger and much more substantial) work better with the stock Cave spur 144 tooth setup?

 

The shaft size is larger on the Hurst though an extension could be added to fit the stock 10 tooth gear.

 

Anyone fooled with this?



#74 bjkaras

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Posted 31 July 2019 - 01:46 AM

I have one of the old Vista drive correctors. It still works pretty well, but my dec drive needs either to be required or just replaced. The Parks scope originally included a single axis control box for the dec drive, so I just removed the capacitor and installed it in the Vista box. It worked just fine. The RA is still good, so I just have to deal with the Dec axis. It has a Hurst CA motor, but I think that one is OOP. Maybe rewriting is the way to go. We shall see.



#75 65&Counting

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Posted 07 August 2019 - 02:21 PM

Question - does the larger drive case on the 12.5" (three screws at the end of the R.A. casting) interchange with the holes on the Cave 10" (and 8") 1.5" shaft mountings?

 

I bought a larger (around 6" diameter) worm gearset that apparently came stock on some Cave's over the 4 1/4" that's on my 12.5 - I also have a 10" mount and want to play with some different setups but it has a smaller case that won't accomodate a 6" worm gear but the 12.5" will - anyone know if they're interchangeable?




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