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Losmandy G11 head, cables, power box, panel, hand controller, and counter shaft. Good condition, but is just gathering dust in the observatory, as I have another G11 in operation. The reason for the sale, is I want to get a bigger mount, so my other G11, would be for a mobile/second mount. Ive not a clue how to price this, ive done some research, but its very hard to find a second hand price. Mount works very well, used it the other day for some solar observing, and tracked good. Ive used it for imaging, using the shoestring astro GPUSB hub for autoguiding via the hand controller and splitter. It doesn't come with tripod, I brought it straight for the pier in my observatory. Obviously collection only as its heavy, and best to see it working. Asking around the £500 mark, ONO. Any questions ask away...….
I've made a video on how to setup an equatorial mount.
Hope this is useful, tips are welcome!
So my birthday just past so money to splash on astro stuff , i will have my 1000D modded by juan at cheapastrophotography and also have ordered an autofocuser from deepsky dad https://deepskydad.com/autofocuser i know they can be done DIY but this is a neat package and costs about the same as a SW autofocuser and a hitechastro focusmaster and i`m no electronic wizard and pavel seems to have a good product and works with ascom and confirmed it works with APT i will update in a few weeks time when hopefully i will have received and tried out .
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.
Repairing a Tal MT3A Mount STEPPER MOTOR Help...
Before anyone says "why bother" let me just answer because I'm not ready to pick up a Losmandy at the moment...
So I have a Tal 200K which I have enjoyed quite a lot. I have always known that the single motor MT3A mount was less than ideal but it works and if nothing else, an 8" Russian made Kletsov catadioptric scope on a super solid peer mount is a pretty good conversation starter, and some of the views I've seen of Jupiter, especially with a 16mm Nagler - well they were amazing...
So a few months ago the mount stopped tracking and slewing at a star party. I could hear that the motor was spinning or making noise, but the mount was definitely not moving under the motor control. I might have just waited and bought something else, but I've had some major expenses plus I'm expecting another due to a large move about to take place so I can't justify spending the money at the moment, BUT I would really like to have a working mount for the Mars opposition in July. So I decided to tear it down and take a good look.
I was able to pull the mount casing apart ... and kept going, largely thanks to the PDF AndyH so kindly shared with me that had all the great teardown photos .. despite the native German which apparently translates into comical English with Google Translate ("Loosen the maggot whisk and the grub screws..." is that right??? )
The part that took me some time was realizng after removing the screws holding the case together and removing the setting circles and springs, that it was pretty difficult to unscrew the collar holding the drive shaft in the mount casing. For that I had to use a long screw placed into a hole in the collar as a kind of spoke to get some leverage to unscrew it. Once it started it was easy. Next I was more apprehensive about the drive shaft- The shaft fits through 2 bearings that had not seen freedom in 15 years, so I had to wack the shaft pretty darn hard from one end to break it free. I did this (again thanks to the photo in the pdf) using a block of wood over the end of the sharft - hitting the wood with a small hammer, and then a larger hammer. Like the collar once it was freed up it was easy to slide it through.
From there I just took stuff apart until I got into the drive gearbox. The small clock-like gear assembly was not difficult to remove and finally I got a good view of the stepper motor. At first I thought the gear was slipping on the shaft but it winds up being more serious. I removed the gear (loosened the 2 grub screws.. or were the maggot whisks?.. ;-) Of course I kept all the little screws in a secure place and tried to keep them attached to their mating parts when possible. But I think I'll be able to reassemble things..
I don't see any broken gears. My idea is to clean them up and lubricate them with a good quality lithium grease.
THE STEPPER MOTOR
I hooked up power and the controller and I clearly saw the drive gear is not slipping, but the motor is slipping, - internally. So I need to either repair the motor which no longer has the torque needed to drive the mechanism, or replace it. There's no way I can get the original motor (Tal is out of the astronomy biz and in Russia), and I don't know the specs about the motor to know how to ID it properly with an equivalent. It may be a type NEMA 17 with 6 leads. They aren't that expensive but will it fit? (looks pretty darn similar) Will the gear fit? Does it take the same signals/control voltages? etc. Alternatively Can the motor be repaired? I don't know much about stepper motors so I have non idea..
I know that stepper motors measure steps in degrees, and I imagine there's a spec that specifies the rate of spin, but I' don't know how to find this out for the motor in the MT3S. I have seen a NEMA 17 stepper motor in Amazon and it's less than $20, has 6 leads and has a 1.8 degree step. I might just take a chance and buy the motor and see if I can figure out the wiring.. if it's the same voltage...??...
I've attached an image of the printing on the motor and a short video showing it's unfortunate behavior.
If anyone has any suggestions how I can move forward I'd really appreciate it.