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Equipment Discussions >> Classic Telescopes

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orion61

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Reged: 10/20/07

Loc: Birthplace James T Kirk
C8 Grounding question
      #5606092 - 01/05/13 07:58 AM

I have an early Sandcast C8 but it only has a 2 prong plug,my
others have the 3 prong shielded cable, I use a drive converter but we are still at 110V AC. outside in dewy grass, Am I going to electrocute myself?


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dgreyson
professor emeritus
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Reged: 11/06/12

Loc: South Carolina
Re: C8 Grounding question new [Re: orion61]
      #5606314 - 01/05/13 10:57 AM

oh Phui!! Man up! Touching your eye to a metal telescope thats wet with dew while standing on a good earth ground?? If your lucky you may just be severely injured.

The synchronus motor windings can overheat, swell up, short against the motor casing and connect 110 volts to the frame.

I doubt the telescope is double grounded if the gears are metal so a three prong plug is better than none. If you need to keep the integrity of your scope as is, just use a Ground fault interrupter extension cable. If you ever get your drive corrector working, you are safe if using a car battery as the power source because the output is isolated and so isnt referenced to ground like line voltage is. If you use the same AC socket, have it changed out to a gfi socket like they put in the bathroom and you can use a regular extension. You still can get a nasty shock until the gfi trips but it should interrupt the current before it gets lethal. ME, I'd use a 3 prong cord and a GFI, but that's only because I seriously plan on outliving my dog.

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apfever
Carpal Tunnel
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Reged: 05/13/08

Loc: Colorado
Re: C8 Grounding question new [Re: dgreyson]
      #5606438 - 01/05/13 11:56 AM

nice disclaimer. No comment.

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desertrefugee
Carpal Tunnel
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Reged: 08/06/07

Loc: Arizona
Re: C8 Grounding question new [Re: apfever]
      #5606823 - 01/05/13 03:21 PM

"Not the Beatles" !??

Then forget it.


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Littlegreenman
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Reged: 05/09/05

Loc: Southern California
Re: C8 Grounding question new [Re: desertrefugee]
      #5606945 - 01/05/13 04:44 PM

Maybe someone knows if running it offer a battery pack reduces any shock or electrocution risk?

Disclaimer This posts has no disclaimers.

LGM


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desertrefugee
Carpal Tunnel
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Reged: 08/06/07

Loc: Arizona
Re: C8 Grounding question new [Re: Littlegreenman]
      #5607041 - 01/05/13 05:56 PM

Quote:

Maybe someone knows if running it offer a battery pack reduces any shock or electrocution risk?

Disclaimer This posts has no disclaimers.

LGM




120VAC is still 120VAC - even if it has been inverted from 12VDC. Power delivery varies by inverter, but in general, most of the same cautions should apply. There's no current limiting in place and the unit will deliver until the fuse/breaker terminates the circuit.

As little as 10mA to the heart will stop it. That's not a lot of current. Given perfect (or imperfect) conditions, moisture, point of application, electrocution could occur.

No disclaimers. Just casual observations by one who works in the cardiac rhythm management business.


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orion61

*****

Reged: 10/20/07

Loc: Birthplace James T Kirk
Re: C8 Grounding question new [Re: desertrefugee]
      #5607066 - 01/05/13 06:06 PM

I have a newer base I could pull the forks off and mount it on that. It is 3 prong, and I wouldn't mess with the origonal base, I couldn't deface it! I'm a huge fan of restoring these old beauties, as a matter of fact I am doing one right now for a friend..
PM for details.. there is a thread about it around here somewhere...LOL


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dgreyson
professor emeritus
*****

Reged: 11/06/12

Loc: South Carolina
Re: C8 Grounding question new [Re: orion61]
      #5607129 - 01/05/13 06:36 PM

Cool, I feel the same, If its something vintage, Id rather have it factory original. Except for my corvette, I had that *BLEEP* tricked out for speed. It got 12 mpg but it would blow the doors off of anyone elses heap. when gas went above 35 cents a gallon I had to reluctantly sell it coz it was taking all my beer money.

As far as Electric shocks go, Wall voltage is different from inverted voltage. Household current is one leg of a 220v circuit that is referenced to earth ground. If you touch the hot lead, current will flow thru you to the ground and shock you. it only takes a single wire. Ive also gotten shocked from the neutral lead as well, dunno why. (used to know but forget) If you touch one leg of an inverter generated circuit, wou shouldnt be electrocuted because it "Floats" above the earth ground. You would need to touch both legs of the inverter output to make a circuit that current could flow through. Thats why I said it was Safer. you would need to bridge across the output to get a shock while AC line will kill you if you touch just one wire or the circuit has a short to the casing. If one side of the inverter output shorts to the casing, you likely would not feel a shock. I'd say you couldnt except I stopped saying absolutes when the second space shuttle blew up. Anything can go wrong.

see legal disclaimer above.


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Littlegreenman
Post Laureate
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Reged: 05/09/05

Loc: Southern California
Re: C8 Grounding question new [Re: desertrefugee]
      #5607202 - 01/05/13 07:50 PM

Quote:

Quote:

Maybe someone knows if running it offer a battery pack reduces any shock or electrocution risk?

Disclaimer This posts has no disclaimers.

LGM




120VAC is still 120VAC - even if it has been inverted from 12VDC. Power delivery varies by inverter, but in general, most of the same cautions should apply. There's no current limiting in place and the unit will deliver until the fuse/breaker terminates the circuit.

As little as 10mA to the heart will stop it. That's not a lot of current. Given perfect (or imperfect) conditions, moisture, point of application, electrocution could occur.

No disclaimers. Just casual observations by one who works in the cardiac rhythm management business.




Thanks for the reply. Now I know.

I think I'll get a gravity driven clock drive...


SL


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dgreyson
professor emeritus
*****

Reged: 11/06/12

Loc: South Carolina
Re: C8 Grounding question new [Re: Littlegreenman]
      #5607276 - 01/05/13 08:50 PM

[quote
Thanks for the reply. Now I know.

I think I'll get a gravity driven clock drive...





You would only mash your toes when you drop a weight and get gangrene. Or you could put your eye out if the mainspring broke or something. No, It's much safer if you get someone else to look thru it and describe what they see to you. You might think that if you stayed home and let them sketch it on a paper and bring it to you that would be safest but your wrong. Because their nasty germs would be on it and you may catch a desperate illness. No no.


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orion61

*****

Reged: 10/20/07

Loc: Birthplace James T Kirk
Re: C8 Grounding question new [Re: dgreyson]
      #5607302 - 01/05/13 09:06 PM

You know if some one could come up with an inexpensive Wind up Clock drive, I'd be ALL over it for general observing!
I'd even try it with go-to... just give me that BIG key
like the Robots in the 50's had in back LOL
I'm serious tho about having a visual mount with a mechanical clock drive.. they could be made...


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johntrob
sage
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Reged: 03/14/11

Loc: Georgia, USA
Re: C8 Grounding question new [Re: orion61]
      #5607377 - 01/05/13 10:05 PM

Remember the old refrigerators, grab the handle and get a charge, still alive.

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dgreyson
professor emeritus
*****

Reged: 11/06/12

Loc: South Carolina
Re: C8 Grounding question new [Re: johntrob]
      #5607581 - 01/06/13 12:00 AM

we had an old metal chest freezer on the concrete carport slab and if you forgot you were barefoot and grabbed the handle to get something it would knock the fool out of you.
I'm sure it could have killed someone under the right conditions, say wet concrete. The adults never knew it of course because they always wore shoes. But it was nowhere near the shocks I used to get from Microphones when I was in a band and they had the amp plugged in wrong so I never thought much about it or told anyone. Just part of doing business I guess.


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dgreyson
professor emeritus
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Reged: 11/06/12

Loc: South Carolina
Re: C8 Grounding question new [Re: orion61]
      #5607590 - 01/06/13 12:03 AM

Quote:

I'm serious tho about having a visual mount with a mechanical clock drive.. they could be made...




I wonder how troublesome the mechanical drives were on Unitrons? they used weights on a chain like a grandfather or a cukoo clock.

here is a thread about them
mechanical clock drives - post a picture


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actionhac
Post Laureate
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Reged: 08/09/08

Loc: Seattle
Re: C8 Grounding question new [Re: dgreyson]
      #5607640 - 01/06/13 12:48 AM

It wouldn't hurt to ground our 110V drives.
Its surprising how easy it is to kill one's self.
I guess we don't think of the danger because we can't see it.
We can buy a appliance cord with a 3prong plug and connect white-white, blk-blk, and ground the green to the drive motor mounting bolts.
Or a 6ft 3prong extension cord and cut off the female and hard wire it in the same as above.
I know its not original but it may save a life under the right circumstances.
Have I done it myself? no I haven't! I'm so lazy. No that's not really it I'm a real stickler for originality is the real reason and yes it will be chiseled onto my tombstone no doubt.
I've been shocked many times, I work with electricity in my job. Sometimes its just a little tingle and other times it has left me with a sore arm. A few times I blinded myself for the rest of the day.

Robert


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DAVIDG
Post Laureate
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Reged: 12/02/04

Loc: Hockessin, De
Re: C8 Grounding question new [Re: actionhac]
      #5608157 - 01/06/13 11:41 AM

I just checked my two old sand cast C-8 mounts with the two prong Jones plug. There is Continuity between the motor housing and the unpainted back of the mount, but none to any painted section of the mount.
While the paint is not a perfect solution it does provide some protection.
A simple solution is to make up a new cord using a three wire grounded plug. At the Jones plug, pull out the green grounding wire and attach it to one of the screws that hold the male Jones plug into the mounting base. Now the scope is grounded as long as you use a grounded outlet with hopefully a GIF on it.
I also have Criterion RV-6 and when I restored in many years ago, I replaced the original cord with a three wire molded one and attached the ground wire to one of the bolts on the motor mount.

- Dave


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tim53
Postmaster
*****

Reged: 12/17/04

Loc: Highland Park, CA
Re: C8 Grounding question new [Re: orion61]
      #5608308 - 01/06/13 12:56 PM

Quote:

You know if some one could come up with an inexpensive Wind up Clock drive, I'd be ALL over it for general observing!
I'd even try it with go-to... just give me that BIG key
like the Robots in the 50's had in back LOL
I'm serious tho about having a visual mount with a mechanical clock drive.. they could be made...




a couple years back, I bid on a drive base for a 70s C8 that was made by Optica b/c, IIRC. Very cool unit with a worm drive. Though not original to the scope, it was of the same vintage. Kind of like one of those retrofits to the C-14 drive made by Ed Byers, only this one was entirely non-Celestron manufacture.

I'm pretty sure it was 110V, though Matters little, as I lost the bidding.

-Tim.


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PiSigma
Carpal Tunnel
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Reged: 10/14/09

Loc: North Carolina
Re: C8 Grounding question new [Re: DAVIDG]
      #5608316 - 01/06/13 12:58 PM

In order to keep my scopes original (two prong plug, ungrounded) and safe I have made up a cord with just the ground wire at the AC plug and an alligator clip on the other end. I run a grounded extension cord and power strip to the scope and plug the scope and my extra ground lead into the strip, then clip the alligator clip to the scope's motor housing. Everything is then grounded and originality maintained.

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tim53
Postmaster
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Reged: 12/17/04

Loc: Highland Park, CA
Re: C8 Grounding question new [Re: tim53]
      #5608340 - 01/06/13 01:08 PM

Does anyone know of DC servo motors that wouldn't need more room than the stock Synchronous motors in the C-8 drive base?

Because, if there are, and they have encoders built in like the Pittmans (which are too big to fit the space in a Celestron drive base), I could imagine converting one to goto with all the cool software like PointXP that comes with the Sidereal Technology goto kit. Within wide limits, you can set the drive rate for specific gear ratios in software.

I did this with my Tak Em-500 mount for about a year or so before Dave Groski repaired the original non-goto controller for me (that I'd fried an IC on because I thought ALL Taks were 24V, but the old ones weren't). Worked very well, though I never used the goto feature because I used the mount for planetary only at the time. Still have the Sitech kit to put in/on another mount, but I'll probably put it on the big Springfield mount I bought a few years ago, which has no drive as yet (no motors, that is, it's got an 11" RA gear!).

I don't like dying before I'm spent, and I'm hoping that's going to be a long time from now. You guys are scaring me about these old AC drives, now. I wouldn't be averse to converting a classic to a DC system if (and only if) it could be completely reversible. Bolt-in only for me for some of these old scopes. If I made such a conversion, I'd keep the original parts - kind of like we keep those screw in sun filters that come with our classic refractors - so everything could be put back to original as the scope's value increases to warrant that.

-Tim.


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orion61

*****

Reged: 10/20/07

Loc: Birthplace James T Kirk
Re: C8 Grounding question new [Re: PiSigma]
      #5608350 - 01/06/13 01:14 PM

I remember as a Kid we used to have a lawn Mower with a big wind up crank that would turn the motor over when released.
It worked great i wonder why they stopped making them..
We have a Clock maker/Repairman who still works on the old time clocks,pocket watches and anything with gears.
I ownder if he could think of something. I'll bet
there would be a market in the Classifieds for us old timers that would appreciate such crafstmanship!
I know I would buy one in a heartbeat..


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