CGEM-DX mod

[miki63au]

Hello everyone,


A report of how I modified my CGEM-DX after I run it over with

my UTE :sadeyes::scared: ...was very depressing to be such an idiot :mad2:
Still, I learned a lot...


I bought a drive system from EQDRIVE (no association with the seller in Ukraine). Initially I intended to use it with my work-in-progress-for-eva'

Byers EQ mount.


However the accident forced me to reconsider, and installed the stepper driver with my friends help. 3d printed flange, adapters etc.
Cut the story short, it works :D


Lots dead-end try and mistakes... software issues... learning EQMOD etc.
The ASI 120MM guide cam tricked me and went on the wrong tangent for a while .... I use 224mc now.


Tracking, go-to is great.


The pics I took is not worth publishing ... just share it what the mod can do.
Some reason the narrow-band filters not combine well... the Ha is wrong size/angle/offset? Not sure what I did wrong... the tracking was great and I think focus was spot on, see Ha pic. Have to work on how to merge narrow-band files :screwy:


Cheers,
Mick

[miki63au]

See pic for a 3:1 belt drive stepper motor ...
Cables thrue the RA shaft, and the eq head is on a pier.

M

[ChrisV]

Nice mod Mick, even if the reason for doing it wasn't so good.

How did you attach the pulleys to the worm drive shafts?
And are they 12/60 tooth pulleys? What steppers have you used?

[miki63au]

Thnx Chris,
The pulleys are 16:48 (I think :screwy:)


I bought big steppers with the EQDRIVE unit. Initially I made a 3d printed interface to attach the motors direct to worms.
Did work, but had issues.

One is to ballance the mount... with that much weight in offset, was never perfect.
And then I had that unpredictable jump with guiding. I decided it may be for the flex-coupling between motor-shaft and worm extension. The CGEM has a worm shaft with flat bit sticking out just enough to attach the coupler.
Then I bought two smaller Nema17 motors and installed the motors inside with the 3:1 drive. Friend mashined interface pulley to worm.
Nice and quiete...
But, it turned out the 120MM ASI camera had issues... so the jumping PHD2 guide stopped when I swapped over to a 224mc ASI. Go figure.


That test night I had RMS 0.3" with p-p around 1" ...happy with that.
And no coffe-grinder noise when do go-to :)


Still learning EQMOD ... bought a game-pad to control the mount. Works like a charm.:thumbsup:


Cheers,
Mick

[miki63au]

See att pics or PHD2 with current arrangements. Steppers inside and pulley to worm.
The other pics illustrates the direct drive with a bigger motors. I believe it would work and not need the bigger motors, but fiddly to balance the mount.

M

[ChrisV]

Very nice. Necessity is the mother of ... etc
Wish my guiding accuracy was as good. So - what sort of truck should I use ??

[miki63au]

Truck?

[miki63au]

Oh... I get it :rofl:(a bit slow, busy with life issues)

No, don't use truck... I did damage to the RA worm gear.
As a gamble swapped to the DEC.
Did the job, as you can see.
In my humble opinion, the CGEM's biggest issue is the gair-train in the motors. Servo drive needs reduction gear. The CGEM has a 50:1 ... using cheap tiny sprockets. With lots of noise, superimposed to the tracking.
The benefit of the stepper based system is the lack of this gairtrain... the drawback is the lack of position feedback.
Sync near by stars rectify that.

M

[ChrisV]

Agreed. The step down gear in the motor is not great. That's where a pile of the backlash comes from too.

I've added steppers and belts/pulleys to an EQ5 and it's quite amazing what it can do for live imaging. The CGEM mod seemed a step too far for me though - I'm mechanically limited