Regarding DIY Star Tracker

[TusharBhardwaj]

Hello Everyone, I have some questions about a DIY Star Tracker. 

1. I am confused with the choice of motor i should use. I'm NOT making a Barn Door Tracker. What i wish to make is more like the trackers commercially available.
2. I understand that those commercial trackers use complex worm gear trains, and what not, to achieve the tracking speed. But i was thinking isnt it possible to make a tracker with a servo or stepper motor coupled with arduino and program the board in such a way that the motor shaft rotates at 0.0007RPM, ie, 1 rotation per day. (Looked up this conversion on google and dont have much ideas about motors).
3. I tried programming the arduino with a DC motor of 200 RPM (have 3 of those). I was sending pulses for 10ms, after every 10ms. This isnt in any way precise speed of tracking for any object. I was just trying out the codes and checking the torque. I soon realised that the torque was so low that if held between thumb and index finger, the shaft stopped. So now i know that the DC motors i have, wont work for the desired output. Thats why i am looking for options that can carry or drive at least 2kgs of stuff (DSLR+a widefield refractor).

I dont have a refractor now but i plan to buy one by December. Currently I use my Phone.

Edited June 21, 2020 by TusharBhardwaj
Removed some unnecessary details. Sorry.

[Davey-T]

Hi and welcome to SGL. it should be possible to make something that only tracks in RA using a stepper motor, pulleys and belt drive.

Do you have access to any power tools or machine tools ?

Dave 

[TusharBhardwaj]

No I dont have any kind of access to machine tools. 

 

[Davey-T]

2 minutes ago, TusharBhardwaj said:

No I dont have any kind of access to machine tools. 

 

Do you know anyone with a 3D printer ?

Dave

[TusharBhardwaj]

I dont know personally but i there must be some online service that can like take the .cad/.svg files and print them.....

[MarkAR]

I've always wondered if something like this could be used.

https://www.arceurotrade.co.uk/Catalogue/Workholding/Rotary-Tables/4-Rotary-Table-with-Stepper-Motor

They also do a larger 6" version.

[TusharBhardwaj]

I am not sure about the 3d printing service availability.... Couldnt get satisfactory answers

 

[TusharBhardwaj]

14 minutes ago, MarkAR said:

I've always wondered if something like this could be used.

https://www.arceurotrade.co.uk/Catalogue/Workholding/Rotary-Tables/4-Rotary-Table-with-Stepper-Motor

They also do a larger 6" version.

Does it rotate at the sidereal rate or is configurabble to that rate??

[Davey-T]

This might give you some ideas

Dave

 

 

[MarkAR]

1 hour ago, TusharBhardwaj said:

Does it rotate at the sidereal rate or is configurabble to that rate??

You should be able to configure the rotation rate. I have no idea about the programming side of things on how to do it.

[TusharBhardwaj]

Just now, MarkAR said:

You should be able to configure the rotation rate. I have no idea about the programming side of things on how to do it.

Ohh Okay. Thanx. 

[TusharBhardwaj]

1 hour ago, Davey-T said:

This might give you some ideas

Dave

 

 

This is nice stuff. This cleared many of my wrong calculations.   

Thanks Davey.

[TusharBhardwaj]

Guys, I found this instructables link -  https://www.instructables.com/id/Two-Axis-Star-Tracker/

I like the design of this model. Its sleek and the guy who posted has explained how it works.

But i have to make it slightly larger so that the future setup of mine can also work with it.
Thats why i asked about larger motors and larger weight/Torque capabilities.

Also, The instructables link has a link that takes us to a github repositiry. I downloaded all those files and changed their extension to .ino from .cpp so that i can read  and manipulate them on arduino. But there are modular programs in there, different file for stepper, different file for real time clock..... How do i convert those codes in a single file that can be uploaded to the board???

Was i wrong when i converted the extension to .ino from .cpp?? Does it harm the code in any way??

 

 

My phone weighs 380 grams and the phone holder is 170 grams, so i need a way to move this ~700 grams setup at the rate of movement of stars. Not only this, I am also saving up to buy a small telescope, and the one i have in mind is 1.4 kilograms. So if i couple the telescope with my DSLR camera, the weight goes somewhere around 2 kilograms. So i wish to make a tracker that can have the payload capacity of at least 3 kilograms so that the gears or the motor don't have to over-exert themselves. I know it would be overkill for my current setup but it will be perfect for the future setup i wish to have.

[TusharBhardwaj]

With help from the community at Arduino Forum, i realized i was thinking it from an inefficient perspective.

I should try to find a solution to the structure that's gonna hold the payload and it's free movement along both X and Y axis... This way motors would have to exert themselves the least while powering the movement.

 

I'll be back when i find the solution.

Wish me Luck