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 [email protected]