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Messages - RAF_Blackace

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AstroEQ Support / Re: Need help with Declination axis Stepper Motor.
« on: September 16, 2018, 01:41:28 »
good news, the 0.8 amp motor is fitted and works fine.

Everything is finished with the platform, all I need now are some clear nights. :)

I think I may have found one that may do for what I want.

I would still like to know if it is possible to use the 1.68 A NEMA 17 motor though if it is only used infrequently?


This is a picture of the current arrangement with a DC drive. This drive needs changing to a stepper motor.

AstroEQ Support / Need help with Declination axis Stepper Motor.
« on: August 27, 2018, 20:55:10 »

I am changing my DC motors on my equatorial platform to steppers but am having trouble finding one for the declination axis that conforms to the requirements.

This motor raises and lowers around 50kg through a lead screw and has an effective worm gear ratio of 1:3600

It requires around 2N/m torque to drive it reliably (1.4 N/m normally). I can use anything from 1:5 to about 1:20 gearbox for this stepper motor to get the required torque.

But the only motors that fit this are Nema 17 motors at 1.68 amps per winding.

I was wondering, since this motor seldom runs, and it should need no holding power since the platform would not move if the motor was switched off. Is there anyway I could use the DRV8825 to drive it? I know the driver would get hot, but it can supply more then the 1.2 amps if it only needs to do so infrequently.

I have no intention of slewing the drive, it's an equatorial platform after all so it's not possible to do that. All the declination motor would be required to do is to adjust the Dec axis during auto guiding. So it would probably run no longer than 10 seconds every few minutes or so.

What do you think?

Or does anyone know of a NEMA geared stepper with a gearbox anything between 1:5 and 1:20 that gives 2N/m at the gearbox output and draws around 1.2 amps a winding?

thanks for the help.

General Discussion / Re: A strange design.
« on: July 22, 2018, 18:08:47 »

I don't know if this can help you, but if you are ussing EQASCOM to interface your mount with the guiding software, then you can define the mount limits. I've atached a pdf file that I've found on internet with some explanations

regards and good luck

Thanks for the information. I can't see any reason why it would not work it theory. I just need to be aware of, or somehow disable to go-to functions as they would simply spin the motors and make the platform go nowhere. Once it's moved to a RA and Dec position I would then need a way of telling the controller it was actually there. Then the tracking would be as normal.

General Discussion / Re: A strange design.
« on: July 21, 2018, 03:48:39 »
This is a picture showing the simple RA drive train.

1. Drive shaft support.
2. Main drive wheel.
3. Simple Heath Robinson lock to lock the platform in any position.
4. Main drive shaft.
5. Link to drive motor.
6. Drive motor Mount.

General Discussion / Re: A strange design.
« on: July 21, 2018, 03:39:18 »
Just to give you an idea of how well it tracks. If I position an object in the centre of an 8mm eyepiece (0.6 degree field of view) after 1 and a half hours it is still in the field of view, albeit it has shifted slightly in declination and RA. The RA could be adjusted by trimming the speed of the RA motor but that is old school. I want to get closed loop control with a tracking camera.

Hoping to get some advice.

General Discussion / A strange design.
« on: July 21, 2018, 03:32:57 »
Hello all.

I built myself an equatorial platform for by Dob and it tracks surprisingly well. But not well enough for deep sky astrophotography. But I see no reason why I can't make it good enough to do that.

Some background. I built it from a design I found on the internet. Currently it uses a simple astromaster drive motor at 9.5 revs per hour. This tracks well but as it is a DC drive it does need adjusting as the load shifts.

I am now considering replacing this drive with a stepper motor, also I am making a declination drive adjuster that should give me +-2 degrees declination adjustment.

The ultimate aim is to use auto tracking using PHD2 guiding with guide camera.

So far from being a go-to mount, or having the capability of moving to anywhere, I simply want a solution that tracks using a guide camera.

My Equatorial platform gives me a maximum 1 and a half hours of RA tracking, currently it is incapable of Dec tracking but I'm designing a solution for it.

My question is.

Is ASTROEQ a possible design interface between the tracking camera and the drives (both of which will be stepper motors but would obviously be limited in their possible movements).

I'm at the early stages of the design and looking for help, so any would be greatly appreciated.

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