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Great Polaris Question

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#1 mcwolfson

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Posted 23 August 2012 - 08:02 AM

Just picked up a used EQ mount which I think is an older GP. It has encoders and motoros and clutches, but no hand control. The cables look to be 7 pin DIN. Anyone know what kind of hand control will work with this, e.g. DMD-1 or 2 or 3? If so, would anyone have a spare hand control? Thanks much -- Michael

#2 gnowellsct

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Posted 23 August 2012 - 04:52 PM

Just picked up a used EQ mount which I think is an older GP. It has encoders and motoros and clutches, but no hand control. The cables look to be 7 pin DIN. Anyone know what kind of hand control will work with this, e.g. DMD-1 or 2 or 3? If so, would anyone have a spare hand control? Thanks much -- Michael


Picture of the mount, to verify it is in fact a GP, and with a close up of the motors, is needed. Greg N

#3 Geo.

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Posted 23 August 2012 - 06:25 PM

7 pin DIN are the later stepper motors. Certainly not the DMD-1. The answer is an expensive one.

#4 mcwolfson

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Posted 23 August 2012 - 06:36 PM

Actually, I made a mistake. The DIN plugs have 7 pins around most of a circle, plus one pin in the middle. I'm trying to add a photo... Thanks -- Michael

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#5 jrcrilly

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Posted 23 August 2012 - 06:54 PM

Actually, I made a mistake. The DIN plugs have 7 pins around most of a circle, plus one pin in the middle. I'm trying to add a photo... Thanks -- Michael


Sounds like the MT-1 motor. SD-1 (single) or DD-1 (dual) controller.

#6 TONGKW

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Posted 23 August 2012 - 09:49 PM

I have also acquired a Vixen SP mount head with a faulty RA motor and control box for a very low price.
I bought a single axis EQ3 single axis motor drive from China for about US$60. I removed the internal parts from the old electric motor and fitted the internal electrical parts from the EQ3 reusing the old gears. My friend modified the electronics of the EQ3 control box a bit for me to suit the gear ratio. It works but I have to remember the 6-volt electrical supply has now to be center pin positive.
Here is this SP eq. mount adapted to fit onto a old Gitzo photo tripod and with a vintage Astro 3” f/18 achromatic refractor. This set up is a favorite at star parties.

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#7 orlyandico

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Posted 24 August 2012 - 12:03 AM

You can also buy the drive for the Orion Sky View Pro. This fits the GP and the whole thing (motors, drive controller, the works) costs $120. Much less than the cost of a DD-1!

You could even sell the two MT-1's that you have (which are worthless without a DD-1) for $50 a pop. That would take you most of the way to an Orion drive.

Or if you are handy with an Arduino (or similar) you can make your own stepper controller for the MT-1's and add fancy stuff like ST-4 autoguiding and Periodic Error Correction. Google "starjar MT-1" for the pinouts. The motors are Nippon Pulse 48 pulse per rev, unipolar steppers, with a 120:1 gearbox. Dead-simple to drive, if you're anywhere handy with electronics.

#8 mcwolfson

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Posted 24 August 2012 - 09:32 AM

Thanks for these thoughts! Perhaps a crazy question: any chance that an older DMD-1 with 5 pin DINs could simply be rewired to 7+1 pin DINs, or is the circuitry designed for another stepper motor entirely?

#9 SteveInNZ

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Posted 24 August 2012 - 05:15 PM

It works but I have to remember the 6-volt electrical supply has now to be center pin positive.

On my SP mount, I put a bridge rectifier inside the hand controller. Using the wrong power lead was too high a risk for me. Now it's 12V like everything else and there was space to put a reasonable sized capacitor in there too.






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