DSLR Star tracker

I set out to create my own design for a basic star tracker. I decided against a barn door design, in favour of a more compact gear driven design. This is still a work in progress.

Here are the parts I printed. I printed them all using standard PLA at 0.2mm on an Ender 3, with exception for the worm gear. I ended up printing it with a resin printer, however I had previously printed it at 0.08mm and it worked okay too.

 

Parts print list

Filename	Quantity to print
Ball head mounting plate.stl	1
Gearbox A.stl	1
Gearbox B.stl	1
Gearbox C.stl	1
DIN RA adapter.stl	4
Bearing base.stl	1
Bearing cap.stl	6
Worm gear.stl	1
Worm wheel.stl	1

 

Parts list

Component	Quantity
M6 nut	50
M6x10mm Button head	15
M6x16mm Countersunk	3
25x160mm Aluminum bar (1/8" thickness) (OPTIONAL, but reccomended)	5
6003-2RSL bearing	1
605ZZ bearing	6
M3x20mm Raised cheese head	12
M3x8mm Raised cheese head	4
NEMA17 42-34 stepper motor	1
DRV8825 stepper driver (or equivalent, needs to have 1/32 microstepping)	1
5mm LED	3
Radial Electrolytic capacitor (min.100 μf)	2
Raspberry pi pico, with header pins	1
GT2 20T and 60T 200mm pulley combo	2
5x60mm metal rod	1
5x120mm metal rod	1
Tripod ball head adapter	1
Custom PCB for electronics* (see more below)	1
M6x80mm coach bolt	1
M6 penny washer	3
3/8″ 16 pitch UNC bolt for tripod ball head	1
JST XH 2 pin connectors male and female	2
JST XH 4 pin connectors female	1
LM7805CV 5V linear regulator	1
Diode	1
A tripod or wedge mount for equitorial tracking	1
DIN Rail 300mm	2

 

*Regarding the PCB, I have attached the ZIP file to upload to JLCPCB/similar to have my design made. As an alternative, you can use your own design for a PCB. The PCB design files can be found here: https://github.com/WaylonGao/picoStarTracker

The key thing is that the stepper motor makes a 1/32 microstep every 1/79.5872 seconds. 

 

Does it work?

Yes! I tested it recently, and it works!

Milky way without tracking:

Milky way with tracking:

I also captured a photo of Deneb and the surrounding area:

Raspberry pi pico code

https://github.com/WaylonGao/picoStarTracker

To upload the code, I used Thonny (https://thonny.org/). I am using Micropython on the Raspberry pi pico.

""" Raspberry pi pico based DSLR star tracker Waylon Gao 2024 https://github.com/WaylonGao/picoStarTracker """ import machine from machine import Pin import utime #Define INPUT pins: adjDown = Pin(0, Pin.IN, Pin.PULL_DOWN) adjUp = Pin(1, machine.Pin.IN, Pin.PULL_DOWN) reverseDir = Pin(2, machine.Pin.IN, Pin.PULL_DOWN) enable = Pin(3, machine.Pin.IN, Pin.PULL_DOWN) fault = machine.Pin(4, Pin.IN) #Define OUTPUT LEDs: pwrLed = machine.Pin(5, Pin.OUT) stepLed = machine.Pin(6, Pin.OUT) errorLed = machine.Pin(7, Pin.OUT) # Define the onboard LED led = machine.Pin(25, Pin.OUT) # Define STEPPER DRIVER pins: resetPin = machine.Pin(8, Pin.OUT) sleepPin = machine.Pin(9, Pin.OUT) stepPin = machine.Pin(11, Pin.OUT) enablePin = machine.Pin(10, Pin.OUT) dirPin = machine.Pin(12, Pin.OUT) m2 = machine.Pin(13, Pin.OUT) m1 = machine.Pin(14, Pin.OUT) m0 = machine.Pin(15, Pin.OUT) T = 1.0 / 79.5872 #rotate at sidereal rate on = 1 adjustment = 0.01 #adjustment to T for button presses def setup(): for i in range(9): print("boop") led.toggle() pwrLed.toggle() stepLed.toggle() errorLed.toggle() utime.sleep_ms(50) pwrLed.toggle() stepLed.toggle() errorLed.toggle() utime.sleep_ms(50) pwrLed.value(1) print("Setup done") setup() #turn on enable pin enablePin.value(0) dirPin.value(1) m0.value(1) m1.value(1) m2.value(1) #Max microstepping resolution (32 bit) # Main loop resetPin.value(1) sleepPin.value(1) errorLed.value(0) pwrLed.value(1) led.value(0) while True: stepPin.value(1) stepLed.toggle() utime.sleep(T/2) stepPin.value(0) utime.sleep(T/2)

 

This is still a work in progress! If you have any questions, criticisms or suggestions, please let me know! My email is gaowaylon@gmail.com