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I have a Helios 200p (identical to the Skywatcher) mounted on an EQ3-2.
I know it is overloaded but I find it OK for visual provided I give it a couple of seconds to settle down at high powers.
I intend to motorise the mount using stepper motors & an Arduino. It will be tracking for visual only with a possible upgrade path to GoTo.
Since I dont need fantastic precision and having read the relevant threads on this forum, I propose to drive the RA worm directly & the DEC with a simple belt drive. By avoiding a step-down gear set I will still be able to use the manual slo-mo controls without disconnecting the motors. I think that centering the target with the slo-mo's & then switching on the tracking will be nicer than using fast-forward & fast-reverse controls.
But no step-down means no torque amplification. So how much torque do you need to drive an overloaded EQ3-2. I decided to do some quick & dirty tests.
200p with 25mm Plossl & 9 X 50 Finder, payload about 9kg.
EQ3-2 with 10kg of counterweights
Improvised wooden pulley, effective radius 0.375 inch
2 X 1kg barbell weights
piece of string
For each axis ,with the clutches locked, a 1kg & then 2kg load was hung from the pulley & released. This was repeated for the opposite direction of rotation.
DEC 1kg Torque 13.5 oz.inch Rotated smoothly at about 90 degree/minute
DEC 2kg Torque 27 oz.inch Rotated quickly at about 300 degree/minute +
RA 1kg Torque 13.5 oz.inch Did not rotate
RA 2kg Torque 27 oz.inch Rotated smoothly at about 90 degree/minute
The required torque for RA would be on the limit for a (cheap, ungeared) NEMA 14 stepper but a NEMA 17 motor with a torque of 84 oz.inch should be up to it.
So now all I have to do is order the bits & learn how to use an Arduino.
As the title says. I'd prefer the RA version, not the one that does both axes. I only use paypal for small payments. I'm in the UK.
By Nick in Kent
I've been getting started with an EQ3-2 GOTO / Skymax 127 combo, and had a couple of queries / concerns about the mount; advice would be greatly appreciated.
With the clutch released, rotating on the RA axis the mount meets resistance when the counterweight bar approaches horizontal. It's enough that sometimes the motor drive can get stuck; there's no clicking from gears skipping, but movement stops. If I undo the RA setting circle screw the resistance is gone so I thought that was my error as the manual says to unscrew when locating, but as tracking is on the RA axis and the screw would normally be tightened at that point, is this an issue with the mount? I'm not expecting to use the circle so I can leave the screw loose and it seems that it'll be fine, but I'm wondering what the issue is. I've looked at badger's teardown, but I really don't want to take it apart yet as it's new and there isn't much backlash and no slop (if I understand the term correctly).
I'm also wondering whether the DEC circle is set incorrectly at the factory and needs adjusting, or is this a misunderstanding on my part. After polar aligning, I assumed that having the arrow on the side of the mount head point to 90 on the DEC circle would have the telescope pointing correctly home positioned, however with a 1 star alignment my home position was clearly incorrect, and after doing a 3 star alignment (and getting good tracking after that) and returning home the DEC circle was around 78. Using a spirit level on the head, if the edge of the mount head that's parallel to the scope mounting plate when it's tightened and horizontal , the DEC circle is around 12 (or 78 if vertical), however if the edge of the head that has the two screws that secure the plate is horizontal, the DEC circle is 0. So it seems as if the DEC circle was set based on the orientation of the side of the head that has the screws, which doesn't lie parallel to the scope mounting plate, rather than the edge that lies snug against the mounting plate. Does that sound plausible or should the DEC circle be at 12/78 when the scope is horizontal or vertical?
Good evening all.
I was on holidays in the south west of Ireland for 10 days and was clouded out for most of it. Last Friday i was lucky and a small break in the clouds allowed me to grab this.
The big blue star on the left is Altair and the orange one near it is Tarazed.
This is 220 30 second subs with the Sony A7s and Samyang 135mm.
Stacked in PI, Processed in PS.
Hope you like it.