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Turning Star Adventurer 2i into a Go-To?

Sky-Watcher Star Adventurer 2i - WiFi Harmonic Mount GoTo
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Alien_Enthusiast avatar
Alien_Enthusiast avatar
Dear AstroBinners, 

I managed to connect my SA2i to NINA! 

Super happy about it!  

So now I need a controllable Dec to turn it into a proper Go-To 

Here is my question; what is the easiest way to motorize the Dec?  

Are there any custom Dec brackets that have a built-in motor that could be attached to SA2i?  

If not, how hard would it be to try modifying the Dec bracket? I could buy some RC components and attach a motor to the slow control output, and then somehow connect the motor to my PC and tell NINA that it is responsible for Dec. 

Any suggestions?

Has anyone done this before? 

I know it may sound silly but I’m willing to try
Engaging
Oscar avatar
Oscar avatar
yikes, turning a star tracker into a GoTo mount sounds complicated

just buy the Planewave company for a couple million bucks and you're good to go!

you could mount that Evoguide 50 to the Planewave L500 gimbal, it would be a pretty pair! heeeehehehehe!! 

I honestly don't know that much about star trackers; up to now, for whatever reason, I was thinking all star trackers already had GoTo; so based on that, you know you can't trust me when it comes to star trackers.

But I found these videos, which might help (they sound related): https://www.youtube.com/watch?v=JfTsTZkUOjo, https://www.youtube.com/watch?v=tNPIMKOB9k4
GTom avatar
GTom avatar
I am not sure if platesolving / astap could give you indication which way to turn the DEC button?
Quinn Groessl avatar
Quinn Groessl avatar
The easiest way to turn a Star Adventurer 2i into a go-to is to sell it and buy a Star Adventurer GTI.
Well Written
Lynn K avatar
Lynn K avatar
Unless you are a expert machinist with thousands intvesed in equipment , this is a bad idea. There is no adequate DEC  gearing on the Star Adventire to accommodate a GoTo mechanics. The included worm gear is only good enough for slow motion sewing.  For what ever it will cost you to modify the dec, that amount would purchase a GTi with the difference. It will not  be as simple as mounting a bracket and motor. 

The Ra is not GoTo capable. It will take hours to slew to an object at RA rate. How do you plan to alter the circuit bord to communicate with the dec motor. How will a simple electrical DC motor going to communicate with the circuit boards to N.I.N.A. 

Lynn K.1.
Tom Gray avatar
Tom Gray avatar
I had thought about this - not for ‘goto’ but to assist with final alignment and better guiding. I made a bracket, and have a waveshare Hat for my RPi4 (for an autofocuser)  but don’t have the coding skills to adapt/make this work.  

It is of course easier just to buy an off the shelf solution / a SA GTi as some do, but not half as much fun, or necessarily affordable for everyone. I have shelved this project until I retire and have more time. Have fun, and share the solution if you manage to do it.
GTom avatar
GTom avatar
That's exactly the kind of "solution" I also had in mind. The great part is that constructing your own drive kit, you have total control on quality, backlash, etc, you can service your gear, replace components anytime, while AZ GTI's and SA GTI's go to the BIN because of their worn planetary gearboxes…
Alien_Enthusiast avatar
Alien_Enthusiast avatar
Tom Gray:
I had thought about this - not for ‘goto’ but to assist with final alignment and better guiding. I made a bracket, and have a waveshare Hat for my RPi4 (for an autofocuser)  but don’t have the coding skills to adapt/make this work.  

It is of course easier just to buy an off the shelf solution / a SA GTi as some do, but not half as much fun, or necessarily affordable for everyone. I have shelved this project until I retire and have more time. Have fun, and share the solution if you manage to do it.

Wow thats amazing! Where can I buy one?
Tom Gray avatar
Tom Gray avatar
The waveshare is a commercial HAT for RPi4 which can run 4 stepper motors. I use one to work my focus system using code shared on indi forums. It works but added too much weight to my SA 2i. I made the bracket (photos at the link). 

Lots of folks have done similar with Arduino. PHD2 sends pulses via ST4 so in theory it ought to be possible to direct these to a stepper motor, but I doubt guiding accuracy would be great - hopefully good enough for a widefield lens.
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Alien_Enthusiast avatar
Alien_Enthusiast avatar
Tom Gray:
The waveshare is a commercial HAT for RPi4 which can run 4 stepper motors. I use one to work my focus system using code shared on indi forums. It works but added too much weight to my SA 2i. I made the bracket (photos at the link). 

Lots of folks have done similar with Arduino. PHD2 sends pulses via ST4 so in theory it ought to be possible to direct these to a stepper motor, but I doubt guiding accuracy would be great - hopefully good enough for a widefield lens.

Could I order one from you? What would the price be?
Marko avatar
Marko avatar
Alien_Enthusiast:
Are there any custom Dec brackets that have a built-in motor that could be attached to SA2i?

I designed such a thing and 3D printed it. It ended up on my pile of to be finished projects for the time being. Basically I took a stepper motor and a belt on the DEC axis. I used a rotary encoder to get feedback of the position and it worked more or less fine in a sense that I could make it rotate and should be as precise as the 12 bit encoder allows. The nexts steps would be to design a final circuit board and somehow integrate that into software. My plan was to make a little hand controller with a display which just shows the angle, but I wonder if it would be possible to write a driver to use it with real astro software.
However, in the end I just decided to go for a SA GTI and ended up with an AM5 mount instead. But if you want, I could check if I find the STEP files for the design.

EDIT: Forgot to mention: One reason why I did not proceed was that I tested the Goto feature of the Skywatcher App with my Tracker and I got it working, but it made worrying noises like hell and still was painfully slow. So even with a motorized DEC axis, I guess it would not be too helpful.
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Alien_Enthusiast avatar
Alien_Enthusiast avatar
Alien_Enthusiast:
Are there any custom Dec brackets that have a built-in motor that could be attached to SA2i?

I designed such a thing and 3D printed it. It ended up on my pile of to be finished projects for the time being. Basically I took a stepper motor and a belt on the DEC axis. I used a rotary encoder to get feedback of the position and it worked more or less fine in a sense that I could make it rotate and should be as precise as the 12 bit encoder allows. The nexts steps would be to design a final circuit board and somehow integrate that into software. My plan was to make a little hand controller with a display which just shows the angle, but I wonder if it would be possible to write a driver to use it with real astro software.
However, in the end I just decided to go for a SA GTI and ended up with an AM5 mount instead. But if you want, I could check if I find the STEP files for the design.

EDIT: Forgot to mention: One reason why I did not proceed was that I tested the Goto feature of the Skywatcher App with my Tracker and I got it working, but it made worrying noises like hell and still was painfully slow. So even with a motorized DEC axis, I guess it would not be too helpful.

Sounds interesting! I guess software is the big issue here. Hardware part is somewhat doable. But integrating it into a single control software - thats a big deal. Where can I buy the motor you were using?
Alex Nicholas avatar
Alex Nicholas avatar
for the effort and cost involved, if you're only doing it to get the goto mount, sell it and buy the GTI… 

If you're doing it for the passion and learning experience, it would be easiest to do it by replacing the RA motor entirely, then building a belt driven dec axis (3d printed main wheel, motor pully, motor mounting etc, then getting an OnStep controller board. Connect up your motors to the OnStep controller, and then plug in the specifics for the SA2i RA worm/wheel and motor, and the Dec axis main pulley/drive pulley ratio and motors… From there, it should know how far in degrees you move in RA and Dec per stepper motor step (and obviously, per micro-step)… 

Once running and properly tested, you should be able to connect via USB to the OnStep board, issue GoTo commands and pulse guide via the usb cable in both RA and dec… Being a fully belt operated dec, you should experience zero backlash in dec, which should be fantastic for guiding…

That's how I would do it.. 
Though, given the time it would probably take (especially if you're not particularly hands on) and the cost (especially if you don't own a 3d printer, and all the required tools to make all this stuff work, the frustration, cost and attempts before success would FAAAAR outweight the cost of a used HEQ5 Pro, that would absolutely destroy the modded SA2i for overall results. 

Doing this in any way at all that retains the current RA drive system, but adds a declination head is going to be nigh on impossible without a VERY good understanding of writing drivers and firmware that can act as a mediator… basically it would be a software wrapper around the current RA drive motor, that exposes a dec move and ra move command, dec move commands get routed directly to the dec motor via your own arduino based controller, ra move commands would get routed via some other type of physical control that in turn speaks to the RA motor… I wouldn't want to go that route, and I'm a software engineer…
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Marko avatar
Marko avatar
Alien_Enthusiast:
Sounds interesting! I guess software is the big issue here. Hardware part is somewhat doable. But integrating it into a single control software - thats a big deal. Where can I buy the motor you were using?

It is just a standard NEMA17 stepper motor. Motor, driver, encoders, pulleys and belt, I got all from Amazon.
The whole thing looks a bit overengineered, because I wanted the hall-encoder to be coupled to a magnet I glued to the DEC axis (the second pulley, belt and dovetail clamp are missing on the photo).
For control I used a small arduino controller. For just controlling the single axis it should be possible to define a few simple commands which can be sent from a PC via a serial connection with a simple program. But a full integration to combine it with the RA axis is far beyond what I know about programming.
Helpful
GTom avatar
GTom avatar
Alien_Enthusiast:
Sounds interesting! I guess software is the big issue here. Hardware part is somewhat doable. But integrating it into a single control software - thats a big deal. Where can I buy the motor you were using?

It is just a standard NEMA17 stepper motor. Motor, driver, encoders, pulleys and belt, I got all from Amazon.
The whole thing looks a bit overengineered, because I wanted the hall-encoder to be coupled to a magnet I glued to the DEC axis (the second pulley, belt and dovetail clamp are missing on the photo).
For control I used a small arduino controller. For just controlling the single axis it should be possible to define a few simple commands which can be sent from a PC via a serial connection with a simple program. But a full integration to combine it with the RA axis is far beyond what I know about programming.

Adding motorized DEC dithering and integrate that in NINA would already be a huge achievement! If you work on a single target all night, goto slewing isn't important. Dither IS!
Rick avatar
Rick avatar
Hello would one of these be powerful enough to run the Dec axis?  I am very interested in using this.

https://astrowhat.com/reviews/gemini-eaf-electronic-auto-focuser.29/

And connecting it to the Dec shaft

Love to hear your thoughts. 

Rich