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hand controller question

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#1 solshaker

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Posted 11 March 2008 - 11:58 AM

will the hand controller for a an eq3/cg4 drive kit work on a cg5? going by the instructions with the eq3 kit it should, as there are instructions for mounting on a cg5, with the only difference being the brackets used to mount the ra motor and the size of the dec gear.

can anyone advise?

thanks in advance.

#2 John Carruthers

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Posted 11 March 2008 - 01:01 PM

Depends mainly on how many teeth are on the crown wheel (worm wheel), if they're the same you may be in luck. Connect it up and time the worm rate, multiply that by the number of teeth on the wheel and see if it comes out near 86 164.0905 seconds.

#3 solshaker

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Posted 11 March 2008 - 02:52 PM

thanks for the reply, John. a few questions as im fairly ignorant to mount terminology.

which wheel should i be timing and counting the teeth on? im guessing the worm rate would be the time it takes A to make a full rotation? or is the worm wheel a different one (B or C)?

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#4 ccs_hello

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Posted 11 March 2008 - 05:34 PM

For CG5/EQ4/EQ5/SVP the worm ("B") to worm gear ("C") reduction is 144:1.

For EQ3-2, RA is 130:1 while DEC is 65:1.

So the simple answer: the EQ3-2 handbox is not compatible with CG5.

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#5 solshaker

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Posted 11 March 2008 - 11:30 PM

thanks for the reply ccs. let me just make sure i have this right. the two B s confuse me. was that a typo?

so one rotation of the A and B gears travels 144 teeth on C? so the difference between the mounts is the number of teeth on C. the handbox tells the motor how fast to turn to achieve the correct ratio for the given mount.

i was thinking that the electronics in the box gave out a standard signal, and the gears on the motor would achieve the correct speed to make a given mount track correctly since all the motors look to be the same.

#6 ccs_hello

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Posted 11 March 2008 - 11:53 PM

I just corrected my typo, now it's read "B" and "C".

This type of simple design is a simple stepper-based design.
Handbox generate stpeer motor driving pulses, stepper follow the pulses (one to one mapping) to rotate. The stepper then go through a gearbox (typically in 100:1 ~ 130:1 range) onto its final output shaft "A".
Everything is prearranged for the precision timing and teh handbox determines that.
I'm almost certain that (non re-flashable) firmware code inside the handbox determines the correct output pulse rate for the mount system it is pairing with.

"C" will rotate one 360 degree once every sidereal day (86164 sec).
For CG5, "B" will rotate once every approximately 10 minutes (86164/144=598.36 sec).

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#7 solshaker

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Posted 12 March 2008 - 12:04 AM

got it. thanks for the great explanation. :bow:

#8 ccs_hello

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Posted 12 March 2008 - 12:18 AM

You are welcome.

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#9 Dodgy Geezer

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Posted 16 March 2008 - 08:38 AM

I noted this interesting discussion. CCS, where did you get the final drive ratio information? Would the ratio be the same for a Celestron CG4 as for an EQ3-2?

I ask because I have the opposite problem to solshaker - I have a CG4 mount and EQ4/5 drives/handbox. I could get the drives to connect to the final worm with a bit of bodging and some aluminium brackets, but of course the RA drive ratio will be an issue.

A simple method of sorting this would be to make another handbox - I have a circuit using two PICS which will cost very little to make up, but of course I will need to confirm the final drive speed.

#10 John Carruthers

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Posted 16 March 2008 - 10:16 AM

My apologies, I haven't been keeping up with this thread.
Here's a list of some common crownwheel ratios.

Super Polaris mount 144:1 (~10 minutes per rev)
GP / GP-DX mount 144:1
EQ5 mount 144:1
HEQ5 mount 135:1
EQ6 mount 180:1
Fullerscopes usually 359:1 (~4 minutes per rev)
Orion Optics(UK) 288:1 (~5 minutes per rev)
Beacon Hill Telescopes 287:1 and 360:1
Intes Micro ALTER D6 200:1 (RA)

#11 Dodgy Geezer

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Posted 16 March 2008 - 05:34 PM

John,

Very kind of you to reply so promptly, and with so much information. Do you have any data on the Celestron CG4? It looks like an EQ3-2, and it will be comparatively simple for me to drive the motors at a slightly slower speed than an EQ4/5 set, if only I knew what the different ratios were!

Incidentally, this data is not commonly advertised, but it would seem to be a good indicator of the quality of a mount. I assume the higher the final gear ratio, the more accurate it is likely to be?

#12 John Carruthers

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Posted 17 March 2008 - 08:57 AM

Sorry I don't have the CG4 numbers, when we get one in I'll count it and put it on the list.
The number of teeth need not be a sign of excellence,but often is. (Byer's gear sets for instance). They're more often chosen for easy manipulation in the control sets and available gearboxes. I found this in an old file, any use?

>> The mounts Celestron 93522 and 93523 drives can be adapted to (with varying amounts of work) include:

CG-4 drive, 93522 1/11 RPM:

Celestron CG-4

CG-5 drive, 93523 1/15 RPM:

Vixen Great Polaris, Super Polaris, Celestron CG-5<<


(Not sure where it came from or how accurate the info is.)
To be sure, count the teeth :-)

#13 Dodgy Geezer

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Posted 17 March 2008 - 11:49 AM

Jc,

Thanks again for your information (by the way, your web site is most impressive!). Please don't go to any trouble on my behalf - I only wondered if there was a standard place on the web where this information existed.

The figures you have provided are interesting. 1/11 rpm is near-as-**** 130 when multiplied by 1440, so it seems as if the CG4/EQ3-2 has 130 teeth. But the CG5 (presumably the same as the EQ4?) would seem to have 96 teeth if the drive moves at 1/15 rpm? I thought this mount had 144? I would expect a CG5 drive to do 1/10 rpm.

I didn't want to dismantle a working mount if I could help it, so I am happy to work on 130 teeth. If the ratio turns out to be incorrect it's an easy alteration to a PIC program!


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