23 replies to this topic

[No N in collimation]

I have a German equatorial mount -- an Orion AstroView EQ mount -- and am thinking about getting a motor drive so I can be lazy. But it turns out the "EQ-3M" motor drive doesn't have clutch! If you want to point your telescope at something new over there, you have to uncouple the coupler with an Allen wrench (!). Am I missing something? That sounds like a terrible design. That sounds like even more work than I am doing! I can imagine fumbling around in the dark, dropping the wrench, etc. What a bummer. Am I missing something? There has to be a better way. 

 

This is for visual observing. 

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Edited by No N in collimation, 23 February 2021 - 07:55 PM.

[wcoastsands]

In this situation, I disengage the RA axis clutch and move the scope by hand to where I want it, slightly overshooting the target in RA to allow it to drift into the center of view before turning the motor back on. The motor drive I use with my CG-3 has a potentiometer that can adjust speed. If I need, I’ll speed it up momentarily to help recenter the target.

[hcf]

Losing the slow mo control when attaching a RA motor is indeed a problem.

 

https://www.cloudyni...-place-to-rant/

 

You could replace the set screw on the coupler with a bigger head screw which makes it easy to uncouple.

http://www.scopestuff.com/ss_eq3sk.htm

 

Another creative example of unlinking the motor here

https://www.cloudyni...ve-on-vixen-gp/

 

In case you want to try to build your own motor drive ....

 

I built my own motor drive for an entry level EQ mount and was suprised to find, that for some steppers, the shaft rotates when the motor is powered off.  So I now just turn off power to the motor and use the slow motion knob which is mounted on the other side as the motor.  My project also added guiding support which you don't need.

 

https://www.cloudyni...-nano-eq-mount/

 

Nowadays you don't even need to solder like I did. You do need to be able to use a multimeter, and be able to fabricate a bracket for the motor (drilling holes in a L bracket).

Edited by hcf, 23 February 2021 - 09:09 PM.

[No N in collimation]

Your drive has a clutch, wcoastsands? The Orion EQ-3M does not. It has 2 screws that you have to loosen with a hex wrench instead. Grrr.

[Jon Isaacs]

With the Astroview mount, both axes have levers that serve as locks. These can be adjusted so they will slip. Or you can release them to point the scope.

 

The controller has buttons and switches so you center the object using those.

 

I recommend the single axis drive, the declination can be adjusted with the manual slow motion control.

 

Jon

[wcoastsands]

Your drive has a clutch, wcoastsands? The Orion EQ-3M does not. It has 2 screws that you have to loosen with a hex wrench instead. Grrr.

The drive doesn’t. It’s always engaged with the worm screw, but the axis itself has a clutch that allows me to move it independent of the worm. The down side of having the motor in place is that you loose the manual worm control. Have to disengage the axis clutch and move the scope by hand into position before re-engaging the axis clutches.

[PeterAB]

Hi,

 

I have the Celestron CG-4 version of this mount.

 

The only thing you loose with the RA motor attached is the fine motion hand knob.   You can still release the RA axis with the lock lever and point the telescope at will.    You do fine adjustments with the motor and the hand controller.    The down side is the movements with the motor are slow.   You need to unlock the RA axis to move across the sky.   I think tracking is well worth the loss of the hand knob.

 

I agree with the previous poster who recommends a single axis motor.     I had dual axis motors and took the declination motor off.  

 

Peter

Edited by PeterAB, 23 February 2021 - 09:42 PM.

[radiofm74]

Hi,

 

I have the Celestron CG-4 version of this mount.

 

The only thing you loose with the RA motor attached is the fine motion hand knob.   You can still release the RA axis with the lock lever and point the telescope at will.    You do fine adjustments with the motor and the hand controller.    The down side is the movements with the motor are slow.   You need to unlock the RA axis to move across the sky.   I think tracking is well worth the loss of the hand knob.

 

I agree with the previous poster who recommends a single axis motor.     I had dual axis motors and took the declination motor off.  

 

Peter

Thank you for your post: I have the exact same mount, plan on buying the humble "Astromaster" RA motor and was having second thoughts…

[Jon Isaacs]

Thank you for your post: I have the exact same mount, plan on buying the humble "Astromaster" RA motor and was having second thoughts…

 

How are you planning on mounting the Astro-Master drive?

 

My comments and others too were based on the assumption you would be using a true track drive with a controller,  this allows centering with the controller. The Astro-Master drive has a single speed control so if you speed it up to center the object, you will have to slow it down and readjust it each time.

 

Jon

[radiofm74]

How are you planning on mounting the Astro-Master drive?

 

My comments and others too were based on the assumption you would be using a true track drive with a controller,  this allows centering with the controller. The Astro-Master drive has a single speed control so if you speed it up to center the object, you will have to slow it down and readjust it each time.

 

Jon

The thought of getting the Astromaster comes from the fact that many of those buying the CG-4 motor report only engaging the RA axis, that apparently the Astromaster also works on the CG-4 (https://www.cloudyni...motor-for-cg-4/), and that it's simpler and much cheaper. 

 

To your question: the idea was to use the speed knob, center my object and then reduce / increase speed until I'm happy. It will be at least initially only for visual use, and I was assuming it could work. But if you think otherwise, Jon, pray do tell! I think I can afford getting the CG-4 motor if it's worth it.

[Tony Flanders]

I own the Orion SkyView Pro, which is similar. It works fine with the motors engaged, but it takes a while to get the whole thing hooked up, and the batteries are a fair bit of extra stuff to carry. Therefore I use the motors only when attempting astrophotography or hosting a star party. Otherwise, I find it easier just to reach out and twist the RA knob whenever needed.

[Jon Isaacs]

The thought of getting the Astromaster comes from the fact that many of those buying the CG-4 motor report only engaging the RA axis, that apparently the Astromaster also works on the CG-4 (https://www.cloudyni...motor-for-cg-4/), and that it's simpler and much cheaper. 

 

To your question: the idea was to use the speed knob, center my object and then reduce / increase speed until I'm happy. It will be at least initially only for visual use, and I was assuming it could work. But if you think otherwise, Jon, pray do tell! I think I can afford getting the CG-4 motor if it's worth it.

 

I have not used the Astro-Master drive on a CG-4.  I have used the true track type drives on several mounts.  With those, centering is done with buttons, tracking speed is constant.

 

Ralph discussed tracking with the Astro-Master but did not discuss centering, at least I didn't see it.  If the drive speed is adjusted to center the object, then it would need to be adjusted to track again.  The speed control adjustment is somewhat coarse so I don't really know how practical that is.

 

Jon

[radiofm74]

I own the Orion SkyView Pro, which is similar. It works fine with the motors engaged, but it takes a while to get the whole thing hooked up, and the batteries are a fair bit of extra stuff to carry. Therefore I use the motors only when attempting astrophotography or hosting a star party. Otherwise, I find it easier just to reach out and twist the RA knob whenever needed.

 

 

I have not used the Astro-Master drive on a CG-4.  I have used the true track type drives on several mounts.  With those, centering is done with buttons, tracking speed is constant.

 

Ralph discussed tracking with the Astro-Master but did not discuss centering, at least I didn't see it.  If the drive speed is adjusted to center the object, then it would need to be adjusted to track again.  The speed control adjustment is somewhat coarse so I don't really know how practical that is.

 

Jon

Food for thought! Thanks to you both!

[Mrcloc]

I'm starting a project to make my own controllable RA motor drive. It won't be a problem, because as said, you can just loosen the RA clutch if you want to move it manually. You can't anyway move the telescope if the clutch is locked, with or without a motor because of the worm gear. I'm planning on tightening the clutch enough that it can be moved slightly to align, but that the motor will still move the axis along.

[RobertMaples]

The thought of getting the Astromaster comes from the fact that many of those buying the CG-4 motor report only engaging the RA axis, that apparently the Astromaster also works on the CG-4 (https://www.cloudyni...motor-for-cg-4/), and that it's simpler and much cheaper. 

 

To your question: the idea was to use the speed knob, center my object and then reduce / increase speed until I'm happy. It will be at least initially only for visual use, and I was assuming it could work. But if you think otherwise, Jon, pray do tell! I think I can afford getting the CG-4 motor if it's worth it.

If the Astromaster drive can be fitted it will work, but in my experience they are rather aggravating - better than manual, but not a lot better.  The stepper drive types are a lot better, but also a lot more expensive, especially the dual motor ones.  It's too bad they don't have a single stepper version for the CG-4, at least I don't see one.  I have an Orion EQ-1 mount and the single stepper drive that they sale, still quite a bit more than the Astromaster type drive (which I got first), but not as much as a dual stepper drive and you're not paying for a second motor that you really don't need.

 

Again, yes, the non-stepper version will work, but if you can afford it I would suggest the stepper drive, it's just so much better

[radiofm74]

If the Astromaster drive can be fitted it will work, but in my experience they are rather aggravating - better than manual, but not a lot better.  The stepper drive types are a lot better, but also a lot more expensive, especially the dual motor ones.  It's too bad they don't have a single stepper version for the CG-4, at least I don't see one.  I have an Orion EQ-1 mount and the single stepper drive that they sale, still quite a bit more than the Astromaster type drive (which I got first), but not as much as a dual stepper drive and you're not paying for a second motor that you really don't need.

 

Again, yes, the non-stepper version will work, but if you can afford it I would suggest the stepper drive, it's just so much better

Apologies for my abysmal ignorance in the matter:

1. What is a difference between a non-stepper and a stepper motor? Does this relate to Jon's characterization of some motors as "true track drives"?

2. As we're discussing this… I'm still on visual, but might eventually want to dabble in astro-imaging. I think I understood that the Astromaster RA motor would only allow limited exposure time even assuming good polar alignment. Would the dual-axis CG-4 perform better in this respect?

 

Sorry for the silly questions, and I hope that they may be of interest the OP as well! Not my intention to hijack the thread and if you think I'm doing that send me a PM and I'll cease + desist!!

[wcoastsands]

I have the AstroMaster drive on the CG-3. It came as a kit with the AstroMaster 130EQ-MD. It is a bit fiddly, but it will do the job of working the worm so you don’t have to keep working it manually just to track. Does the job good enough for visual, but wouldn’t consider it for photo.

The potentiometer for speed control is smooth, but what you’re doing is basically adjusting voltage applied to the motor. You’ll need to adjust it to best estimate to maintain the target in the center of view, but will also need to adjust as the voltage level of the battery drops. But that second part is considerably less of a concern.

I’ve gotten to be pretty quick with it. It’s purely for visual observing, and I only use light weight scopes like the AstroMaster 130 and Meade 290-P 60/900mm. Once aligned and the speed of the motor is dialed in, which I can usually do by sound, it’ll stay on target without the need to recenter for a good 10min or so.

[RobertMaples]

Apologies for my abysmal ignorance in the matter:

1. What is a difference between a non-stepper and a stepper motor? Does this relate to Jon's characterization of some motors as "true track drives"?

2. As we're discussing this… I'm still on visual, but might eventually want to dabble in astro-imaging. I think I understood that the Astromaster RA motor would only allow limited exposure time even assuming good polar alignment. Would the dual-axis CG-4 perform better in this respect?

 

Sorry for the silly questions, and I hope that they may be of interest the OP as well! Not my intention to hijack the thread and if you think I'm doing that send me a PM and I'll cease + desist!!

The non-stepper drives use a DC motor controlled by voltage and they are not accurate.  It's hard to get the voltage set to accurately track and any variations in friction in the mount or supply voltage throw it off.

 

Stepper motor drives (which the "true track drives" are) use motors that are controlled by a controller that sends "steps" to the motor, so they are very accurate. The drive moves a precise amount for each step, so knowing the gear ratio of the mount the controller knows how fast to send the steps to accurately track.

 

One advantage of the DC drive is it can be used on different mounts by tuning the voltage, whereas the stepper drive is configured for a gear ratio and will only work good on a mount with that ratio; although some people have used them on mounts they weren't designed for by replacing a crystal on the circuit board to adjust the drive frequency.

 

For basic astrophotography the stepper drive would be much better.

[dmgriff]

In my experience the Astro Master will fit on a Celestron CG4, but, depending on your ota it may not have the "oomph" to push along the ra axis. Did not have enough power for my ED100 f/9 along the RA when I used it on the mount. Maybe handle something with a shorter moment arm such as a 150/750 newt, etc. Probably handle any light weight. Dont know. I had more success on a EQ1 with a 114/900mm newt, which is the class of mount they are designed for.

 

I am not a fan of dual axis drives any more. Single axis RA and controller is really all visual use requires for me. EQ5 Synta single axis RA (with clutch) and controller drives used to be available. I purchased one from a Canadian supplier a few years ago for my EQ5 gems. Not sure if they are still available in US/Canada or anywhere else.

 

Good viewing,

 

Dave

Edited by dmgriff, 24 February 2021 - 12:16 PM.

[hcf]

One advantage of the DC drive is it can be used on different mounts by tuning the voltage, whereas the stepper drive is configured for a gear ratio and will only work good on a mount with that ratio; although some people have used them on mounts they weren't designed for by replacing a crystal on the circuit board to adjust the drive frequency.
 
For basic astrophotography the stepper drive would be much better.

These days it is easy to build your own RA drive controller. A decent motor costs around $22 and an arduino and driver kit around $15. There are many examples of open source controller code for the arduino, which can be adapted for a particular RA gear ratio. The advantage of this setup is that you can use it on other mounts, with just a small software change.  The only problem is that you have to make your own brackets to mount the motor. It is not trivial, but I did mine with L brackets and a hand drill.
 

Apologies for my abysmal ignorance in the matter:

1. What is a difference between a non-stepper and a stepper motor? Does this relate to Jon's characterization of some motors as "true track drives"?

2. As we're discussing this… I'm still on visual, but might eventually want to dabble in astro-imaging. I think I understood that the Astromaster RA motor would only allow limited exposure time even assuming good polar alignment. Would the dual-axis CG-4 perform better in this respect?

 
The accuracy of the Astromaster drive is fine for visual. The problem with the Astromaster DC motors for AP is that it is very hard to get the accurate tracking rate needed or AP. I still was able to take 20-30second shots using it for short durations. But a lot of time is spent tweaking the potentiometer.
https://www.astrobin...332430/?nc=user
 
With the stepper, maintaining accurate speed is much easier. However depending on the mount and the scope it might still be very hard to go past 30s-1 min exposures. This is due to periodic error on the RA axis. You will have to add guiding, so you might as well plan for it.
 
Options for guiding (on a manual mount) are:
1. Build your own RA drive. ONSTEP is good path to follow, if you are build one of their compatible designs, all the software is available. You get GoTo as well with this setup. You can do a simpler drive without ONSTEP, but connecting it to existing AP tools can be tricky.

https://www.cloudyni...-nano-eq-mount/

2. Some of the dual axis drives, can be easily modded to add a ST-4 guiding port. No GoTo, but you can guide.
3. Get a GoTo dual axis drive with a guiding port. Not sure if one exists for the CG-4, though.

[SteveG]

I have the AstroMaster drive on the CG-3. It came as a kit with the AstroMaster 130EQ-MD. It is a bit fiddly, but it will do the job of working the worm so you don’t have to keep working it manually just to track. Does the job good enough for visual, but wouldn’t consider it for photo.

The potentiometer for speed control is smooth, but what you’re doing is basically adjusting voltage applied to the motor. You’ll need to adjust it to best estimate to maintain the target in the center of view, but will also need to adjust as the voltage level of the battery drops. But that second part is considerably less of a concern.

I’ve gotten to be pretty quick with it. It’s purely for visual observing, and I only use light weight scopes like the AstroMaster 130 and Meade 290-P 60/900mm. Once aligned and the speed of the motor is dialed in, which I can usually do by sound, it’ll stay on target without the need to recenter for a good 10min or so.

I put one on a Polaris mount. Same experience as you. It works, but you constantly will be playing with the speed control as the 9V battery slowly drains. The RA stepper motor and a controller is the way to go. Single axis drives are preferred for visual. KISS.

[wcoastsands]

One thing to consider when using a 9V battery is to use a rechargeable Li-ion battery. While Alkaline batteries will tend to have a linear drop off in voltage over the life of the battery, the Li-ion battery will dip in voltage initially but maintain close to the same voltage for most of the remaining battery life before a steep drop at then end. You won’t have to fiddle as much with speed adjustment.

[hcf]

One thing to consider when using a 9V battery is to use a rechargeable Li-ion battery. While Alkaline batteries will tend to have a linear drop off in voltage over the life of the battery, the Li-ion battery will dip in voltage initially but maintain close to the same voltage for most of the remaining battery life before a steep drop at then end. You won’t have to fiddle as much with speed adjustment.

For home, if you have an outlet nearby you can also get a 9V power adapter and connect it to the Astromaster battery connectors. Some people also macgyver multimeter contacts to the Astromaster motor to know/set the correct voltage for the drive rate.

https://www.youtube....h?v=DZDT_scDQSA

 

The stepper motors based drives do need a 12V supply/ larger Battery bank than the Astromaster DC motor.

[csrlice12]

Bought the tracking drives on the CG4.... didn't take long to replace them with slomo hand controls.  Hated losing the RA slomo, and the RA motorboard is too exposed and fragile....mine broke just snagging my jacket.  And, truthfully, it was a PIA to get it all hooked up, the twisting wires, messing with the controller, etc.....While I would like a nice tracking or go-to drive, the CG4 drives aren't it.

Edited by csrlice12, 25 February 2021 - 01:10 PM.