3D Adventurer [Equatorial Mount for DSLR]

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Introduction: 3D Adventurer [Equatorial Mount for DSLR]

About: I'm a French mechanical engineering student, I like to design, make things and share them here! My main hobbies are astronomy, astrophotography and 3D printing. :)

As a big fan of astrophotography and 3D printing I had to build my own equatorial mount for my DSLR.

For this project I used Fusion 360 to design all the pieces.

With this instructable you can design your own or you can use my STL files and follow the assembly tutorial.

Enjoy!

Supplies

Electric:

  • 1x stepper motor 28BYJ-48 5V
  • 1x ULN2003 driver board
  • 1x Arduino (I used nano but every arduino will work)
  • 2x push button (I used a double momentary toggle switch)
  • 2x led 3mm (1x Orange + 1x Red)
  • 1x DC jack adapter
  • wires, soldering iron,

Mechanic:

  • 2x ball bearing (10-30-9)
  • 1x metal tube 105~110 mm long with external diameter according to the bearing (here 10 mm)
  • 3D printer + PLA
  • Screws + nuts (I used M2.5 kit)
  • 1x M8 threaded rod + M8 nuts
  • Heavy stuff

Others:

  • 1x DSLR camera + lens
  • 1x Tripod (mine is a Manfrotto Compact Advanced)
  • 1x Camera ball joint
  • 1x Kodak screw to mount the ball joint
  • CAD software if you want to modify the files (fusion 360 is free for students)

Step 1: Purpose

As you know, Earth is rotating, so it is not easy to photograph stars because they leave star-trails.

In astrophotography, we use the "500 Rule" it allows to take pictures of the night sky without noticeable star trails: divide 500 by the focal length of your lens and you will obtain the maximum exposure time. However, with the crop factor of my DSLR it turns out to be the "300 Rule". My lens is a Canon 24mm f2.8 so according to the rule: 300/24=12.5 I can only shoot stars during 12.5s and that is very short to capture enough light from them.

The device I made is tracking stars, that allows to get rid of that rule and shoot as long as we need.

Fortunately the rotation of the Earth is well known, the axis is passing through the north celestial pole and the rotation speed is 1rev/23h56min4s (stellar day)

With that we can create a device that turns on a parallel axis and at the exact opposite speed as the Earth.

It is called "equatorial mount", it is commonly used with a telescope because with only 1 motor it tracks stars.

Some of them are big and really powerful in order to rotate enormous telescopes but some others are small carrying only a DSLR that is what I wanted to make.

It can also be useful to make timelapse according to earth's rotation.

Step 2: Designing

First, 1rev/23h56min4s is slow, very slow. And for my star tracker I wanted as few gear wheels as possible in order to reduce play in the mechanism that is why I didn't make a planetary gear. I decided to make a simple gear reducer with only 2 wheels, one with 10 teeth and the other with 60 teeth, that way, it divide the speed by 6 and multiply the torque by 6, perfect !

The main shaft is made from a copper tube the material is not very important but it must be a tube, you will understand why later. It has a diameter of 10mm because I had some 10-30-9 bearings (those may be oversized but it results in a very reliable revolute joint)

I used a 5VDC 28BYJ-48 stepper motor, which is not very powerful but with the gear ratio it should be enough

As I live in the north hemisphere at roughly 45° latitude I tilted the Manfrotto socket by 45° the adjustments will be ensured by the tripod head.

I designed all the parts using Fusion 360.

on the 2nd picture, pieces with a "*" are not 3D printed.

Step 3: 3D Printing

I 3D printed all the parts on my Creality Ender 3 with those settings:

  • Cura slicer
  • ICE filament 1.75mm
  • nozzle 210°C
  • bed 50°C
  • 20% infill (gyroïd)
  • 0.16mm / 0.2mm layer height
  • no supports
  • Ø 0.4mm nozzle
  • 40mm/s

the total printing duration is roughly 12h.

Here is the Cults3D link to the files: HERE (.stl and .f3d)

Step 4: Prototyping

23h56min4s is equal to 23.9344444...h

1rev/23.934444h on the main shaft --> 1rev/3.989074h on the motor shaft

4076steps/rev on the motor --> 1 step every 3.523s [3.523225s]

The DSLR stays motionless during exactly 3.523s so according to the 500 and 300 Rule : the equatorial mount will work with lens below 142mm focal length on a full frame and below 85mm on a crop sensor.

In order to drive the motor with 4076 steps, there is this Arduino library by tyhenry.

Here is the code to put in the arduino board if you live in the northern hemisphere.

/*<br>Sketch by SimonRob 
3D printed equatorial mount for DSLR
Instructables
*/

int buttonA1 = 0;
int buttonA2 = 0;
int ledOrange = 4;
int ledRed = 5;

#include <CheapStepper.h>

CheapStepper stepper;

void setup() {
  pinMode(A1, INPUT);
  pinMode(A2, INPUT);
  pinMode(ledOrange, OUTPUT);
  pinMode(ledRed, OUTPUT);
}

void loop() {

buttonA1 = digitalRead(A1);
buttonA2 = digitalRead(A2);

if (buttonA1 == HIGH){
  buttonA1 = digitalRead(A1);
  buttonA2 = digitalRead(A2);
  digitalWrite (ledOrange, HIGH);
  digitalWrite (ledRed, LOW);
  stepper.step(false);
  delay(6);
}
if (buttonA2 == HIGH){
  buttonA1 = digitalRead(A1);
  buttonA2 = digitalRead(A2);
  digitalWrite (ledOrange, HIGH);
  digitalWrite (ledRed, LOW);
  stepper.step(true);
  delay(6);
}
while((buttonA1 == LOW)&&(buttonA2 == LOW)){
  buttonA1 = digitalRead(A1);
  buttonA2 = digitalRead(A2);
  digitalWrite (ledOrange, LOW);
  digitalWrite (ledRed, HIGH);
  stepper.step(false);
  delay(3523);
    
}
} 

the member videoenquirer modified the previous code for the southern hemisphere :

Step 5: Assembly

  1. Screw the motor in place with 2x M2.5 screws + nuts
  2. Hammer the bearing on the tube, 20mm from the end
  3. Place those in the corresponding hole of the main body (red piece)
  4. Hammer the second bearing on the top
  5. Place a washer or anything that can be a spacer here
  6. Insert 4x M2.5 nuts where it is needed (here is the example on the big gear wheel)
  7. Screw the big wheel and the support on the tube, tight them enough to make a mark on the tube
  8. Remove those 2 pieces and drill 2 holes at the marks
  9. Sharpen the end of 2 screws
  10. Screw the big wheel and the support on the tube
  11. Insert the M8 nut into the support piece
  12. Screw the M8 threaded rod
  13. Screw a camera ball joint with a Kodak screw
  14. Add counterweight on the threaded rod to balance the mass of the DSLR

Step 6: The Controller

Once printed, screw in place the two PCB (Arduino + ULN2003 driver) and place the components in the box.

Solder wires according to this schematic:

Then plug the motor and clip the lid on the box

Step 7: How to Use It?

  1. Place the star tracker on the tripod (tube pointing to the north).
  2. Screw the DSLR on the ball joint, and add the counterweights on the other side.
  3. Remove the small gear wheel from the motor to release the axis.
  4. Then adjust the counterweight to balance the rotating part, and put back the small gear wheel.
  5. Look into the tube and adjust the head of the tripod the see the North Star into it (you can also use a laser through the tube).
  6. Power on the equatorial mount and enjoy !

Step 8: Astrophotography

Here is my first photography with the mount :

Here is a picture of th milky way,
Canon 750D, Equatorial mount, Canon 18-55mm stm (at 27mm), f/4, iso1600, 196s

You can see that even at 196s exposure, stars stays dots (except in the corners due to chromatic aberations) however there is a motion blur on the trees. If you want them sharp too, you will have to add a motionless picture of your foreground and mix those into Photoshop or Gimp.

on the picture we can easely notice some deep sky objects:

I also practice astrophotography with a telescope, you can see my photos on Instagram ;)

Space Challenge

First Prize in the
Space Challenge

6 People Made This Project!

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167 Comments

1
Fred_76
Fred_76

7 weeks ago

Nice idea and realisation. I have some comments.

The teeth period is 86044/60=23min54s. It means that the time between two teeth is about 24 minutes. Any default on the printing on teeth will reappear every 24 minutes. That is not a big deal because that mount will be used with small focal lengths, 85 mm or lower.

The 28BYJ-48 stepper moter has a very little torque. Only 0,034 N.m. Assuming a friction ratio of 0.6 between the 3D printed gears (especially because there is a huge interference between 6/60 gears), the net torque is 0.034x(1-0.6)x6=0.082 N.m.

The distance between the center of gravity of the camera and the rotation axis is about 15 cm. Therefore the balancing has to be good to avoid the motor to stall. Assuming the net torque of 0.082 N.m, it gives a max camera's vs counter weight unbalancing of (0.082/9.81)/0.15 ~= 50 grams. This is very little before the motor stalls...

You should better use whether a stronger stepper motor or use a larger gear ratio.

A+

Fred

0
SimonRob
SimonRob

Reply 6 weeks ago

Hi thank you for your great analysis, although I never had that issue of stalling motor.

Simon

1
Facoco83
Facoco83

8 weeks ago

Bonjour et bravo pour ce boulot Simon ! J'aimerai faire ce projet mais j'ai pas d'adaptateur manfrotto sur mon Trépied et je ne sais pas me servir de Fusion 360. Est-ce qu'il est possible que quelqu'un fasse une modification pour que le support soit universel? C'est à dire en ajoutant un pas de vis au format 1/4 pour le mettre sur n'importe quel trépied? Si j'arrive à le faire moi même je l'ajouterai sur Cults et mettrai le lien mais je ne suis pas sûre d'y arriver. Merci d'avance si quelqu'un le fait ;)

1
Facoco83
Facoco83

Reply 8 weeks ago

Au final, je crois avoir réussi en cherchant rapidement. Si ça fonctionne bien, je ferai un dépot du model. Merci

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0
mambrax444
mambrax444

2 months ago

Simon,
Project a l'air super mais le lien vers Cult 3D ne marche plus. Peuton avoir un nouveau lien, SVP?

1
mambrax444
mambrax444

Reply 2 months ago

Merci. Tres sympa de ta part.

0
wessel4
wessel4

Question 4 months ago on Introduction

Hi Simon,
Can you post some simple instruction how to adjust rotation speed because of gear ratio changes? I used GT2 gear 100:16 little bit different that original 6:1 .
Advice
Maciej

0
SimonRob
SimonRob

Answer 4 months ago

Hi! yes of course
1rev/23.934444h on main axis
6.25gear ratio (100/16)
-> 1rev/3.8295h on motor axis
4076 steps per revolution
0.0009395h/step
=3.382s/step
=3382ms/step

So just replace the delay value from the program by 3383 (instead of 3523)

:)

0
Edison 2
Edison 2

Question 4 months ago

How the manfrotto is attached to the tripod

0
ferrifilippo2
ferrifilippo2

5 months ago

Salut Simon !! Et merci de partager votre projet. À mon avis, pour chaque focale que vous utilisez, vous devez faire varier le code arduino, au lieu de 3,5 secondes pour 85 mm, si vous utilisez un 100 mm, vous devez réduire le temps de 3,5 à 3 secondes. Ceci est un exemple, je n'ai aucune idée de la variation du code. De toute façon merci.Je m'appelle Filippo et je vous écris depuis l'Italie.

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0
dparyshev83
dparyshev83

5 months ago

Thanks a lot for the tracker!
I made it with some changes to make the code more reliable.
I enclose the circuit and firmware.
Best wishes, Denis.

#include <CheapStepper.h>
CheapStepper stepper;

void setup() {
pinMode(A1, INPUT);
pinMode(A2, INPUT);
}

void main() {
while (digitalRead(A1) == LOW) {
stepper.step(false);
delay(6);
}
while (digitalRead(A2) == LOW) {
stepper.step(true);
delay(6);
}
stepper.step(false);
delay(3523);
}

Снимок экрана 2020-12-23 в 19.00.08.png
0
Arduino009
Arduino009

9 months ago

I am looking forward to my version of this. I am aiming to be able to control the stepper motor over WiFi with an esp8266. (ON / OFF) I am also wanting to make WiFi version of Manis404's Eos controller and hopefully run it off of the same arduino for full WiFi control.

Thanks for the instructable. It was the best one that I could find for a star tracker. Keep up the good work.

0
RaphaelS4
RaphaelS4

Reply 9 months ago

since you will be using wireless communication to control the tracker, you could consider incorporating a sensor with a gyroscope and compass, to have direction and head tilt information, a sensor that could be used would be the gy-80.

0
Arduino009
Arduino009

Reply 8 months ago

Great Idea! I will try to incorporate your idea into the tracker. The hardest bit at the moment is the DSLR controller part. For the moment i could just control the DSLR with something like this.
Thanks Again.

0
Spoocky
Spoocky

Question 9 months ago

Bonjour,
Merci pour ce super design, déjà tout imprimé et en train d'assembler le tout. Je rencontre toutefois un problème avec le moteur, et j'espère que vous allez pouvoir m'aider! Je pense avoir tout correctement branché en fonction du schéma (je n'ai pas mis les leds). Mais le moteur ne fait que vibrer, il ne tourne pas. J'ai même essayé un programme simple de la librairie de CheapStepper, mais uniquement des vibrations. J'ai essayé de changer l'ordre des cables, et même essayer 2 moteurs et 2 drivers, rien n'y fait... des idées? merci d'avance !

0
SimonRob
SimonRob

Answer 9 months ago

Merci ;)
Hmm c'est étrange ton problème... Si tu as essayé différents câblages, différents moteurs, différents drivers et même différents codes je ne vois pas vraiment d'où ça peut provenir, lorsque tu mets mon programme les led du driver s'allument-elles ? Si oui dans quel ordre ?

0
Spoocky
Spoocky

Reply 9 months ago

Merci de ta réponse. Je pense avoir trouvé le pb entre temps... des faux contacts sur mes pins... en changeant ces pins, j'ai bien l'ordre des leds, D/DC/C/CB/B/BA/A/AD qui se repete. Et le moteur semble bien tourner ! Merci en tout cas !

0
SimonRob
SimonRob

Reply 9 months ago

Ah super !

0
Lomic
Lomic

9 months ago

Salut Simon, comment alimentes-tu l'arduino dans ta solution ? Le boitier contenant l'arduino et la carte contrôleur du moteur pend à côté ? (et l'alim aussi?).

À quoi sert la vitesse "rapide" ?

J'ai fait un remix sur Thingiverse afin d'adapter la base à mon trépied photo ;)

Merci d'avoir partagé ta réalisation.

Hâte de voir la V2