Eq3 Dec motor

[bluemaxroe]

Hi All

 

Has anyone got any experience with replacement of the DEC motor on an EQ3 mount?   it's a standard mount, non-goto.    The RA motor is fine with only a little backlash/slop.  the DEC motor is possibly the worst I have seen..it is a good few seconds when changing direction before the gears kick in.

My question is - if I link a stepper motor directly to the worm gear rather than use the gears.....will it work with PHD guiding.   Surely PHD just calibrates dependant on, amount of movement per pulse.   

I don't think I have anything to lose as at the moment I am having to turn off the DEC guiding, as it won't calibrate at all.

 

As for brackets / physical connection.... I am fairly handy with DIY on these sorts of things.

 

thanks for any help. 

 

Andy

[drjolo]

It may work with PHD, but without additional gear box stepper may have too low torque to actually move worm gear   Just for imaging and guide you may misalign polar alignment a little, and it should force declination correction in one way only, so Dec motor will not need to reverse. 

[bluemaxroe]

I think the motor I would get would be more powerful than the standard one, but you may be right about the torque.  Trouble is, as soon as you add cogs, you get backlash.   might try it with a motor I have an see.

[Stub Mandrel]

This is my arrangement for fitting a stepper to an EQ3, pragmatic rather than pretty:

I used gears I happened to have, data from my calculations:

RA worm ratio 130:1

Gear ratios 3.33333:1 and 4.5:1

Stepper steps: 48

Microsteps: 16

Microsteps per reduction: 1,497,600

Arcseconds per step: 0.87