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Thread: My motorised focuser for Astromaster 130

  1. #1
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    Default My motorised focuser for Astromaster 130



    Hi there,

    After almost 10 years gap returned to hobby. I bought Celestron Astromaster 130, but after couple uses I decided it needs motorised focuser. It was really annoying when I tried to set focus and everything was shaking, vibrating etc from the slightest touch. So here it is, few words about it first.
    Initially I though about using two servos connected together, without batteries, but then stepper motor idea shown up. Had to design few parts using tinkercad (my first ever try at 3d designing). Controller can be unplugged from focuser (uses 9 pin connectors), so optical tube can be disconnected from tripod with no wires hanging around. Power is provided through the same long cable which connects controller and focuser, almost at the end with 9 pin connector cable splits for +5V and GND from my 4s 8Ah lipo (that supplies power for NexStar, dew heaters and motorised focuser, using 12V and 5V stabilisation). It's slow, but this type of stepper motor can go up to 15rpm only using 5v, could be modified to bipolar and then use 12V, 30rpm could be achieved. But it's very accurate and can go really slow. Speed is controlled using potentiometer, direction using 2 pushbuttons. Speed can be adjusted either when one of the buttons is pressed, motor works as long as button is pressed and stops when button is released. Only 5 wires of 8 are used for remote, 5V, GND, Pot middle pin, Switch1 and Switch2. 5V common for Switch1, Switch2 and Pot.
    Helps alot with imaging, I've modified microsoft webcam so it sits in focuser instead of eyepiece.

    Parts used:
    28BYJ-48 stepper motor
    ULN2003 stepper driver
    Arduino Nano
    2x 10k resistors (have to be soldered between digital pins (one for each pin, no.2 and no.3) and GND
    10k potentiometer
    2x 9pin connectors (male and female)
    4 meters of 8 wire ethernet cable
    2x pushbutton switches
    plastic enclosure
    3d printed parts
    6mm belt, type GT2, 202mm lenght
    drive pulley 16T, GT2
    couple bolts, screws and nuts

    Here's the code for arduino:
    Code:
    #include <Stepper.h>
    
    int forward = 2;
    int reverse = 3;
    
    Stepper motor(512, 8,10,9,11);            
    
    void setup() {
      pinMode(forward,INPUT);
      pinMode(reverse,INPUT);
        Serial.begin(9600);
    }
    
    void loop() {
      int Speed = analogRead(A0);
      int RPM = map(Speed, 0, 1023, 0, 100);
      int f = digitalRead(forward);
      int r = digitalRead(reverse);
      if(f == 1 && r == 0 && RPM > 1){
      motor.step(1);
        motor.setSpeed(RPM);
        delay(.01);
      }
      if(r == 1 && f== 0  && RPM > 1){
        motor.step(-1);
        motor.setSpeed(RPM);
            delay(.01);
      }
      delay(5);
        Serial.println(RPM);
    }
    And couple photos
    Attachment 170561screenshot.png20180107_004002.jpg20180107_003925.jpg20180107_031003.jpg20180107_030807.jpg20180107_030935.jpg20180107_030915.jpg20180107_140046.jpg20180107_140113.jpg20180107_185717.jpg20180107_185712.jpg20180107_185708.jpg20180107_185735.jpg

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    Default

    That is impressive! Really cool idea and use of an arduino. Talk about colliding hobbies, astronomy and computer engineering... I started getting into arduino myself but couldn't really find useful projects. I can see the 3D printer opening a lot of doors in that respect, like in this case. Thanks for sharing!


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    MarcinM (01-10-2018)

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    Default Re: My motorised focuser for Astromaster 130

    Really nice and compact
    I have build one aswell with Arduino and Easydriver board. Mine i can controll through APT. I have a little to big and powerful stepper (nema17). But anyway it works and that is the main point
    If you want to extend the coding without doing it yourself check out on sourceforge.net where you can get pre-made coding for different applications
    Mikael
    TS-optics photoline 80 triplet+ x0.79 F&R F/4.74
    Guiding: qhy5lll APM 50mm guidescope
    Main camera: Starlight xpress H18 mono +filterwheel (Ha,OIII, SII ,LRGB baader filter)
    Mount:
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    Rowan mod
    Arduino controlled focuser with a nema17 motor
    Programs: APT, DSS, PS, Nebulosity3,Startools, Phd2, CDC Eqmod

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    MarcinM (01-10-2018)

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    Default Re: My motorised focuser for Astromaster 130

    Very creative!

    I have been considering getting a 3d printer but still holding off for a while.

    I was wondering which one you were using as your 'parts' look great! I was considering the one by Creality.
    Scopes: Orion 130mm APO Triplet, Orion 8" f4 astrograph, 10" RC Mount: Celestron CGX-L Guiding: Orion 60mm f4 scope, Starlight Loadstar, PHD2 software - Cams: Planetary: ASI120mc, DSO:Atik 383L+, SGPsoftware Processing : Regisax, Deep Sky Stacker, Star Tools, Pixinsight Assistant: One very large cat
    ~ Put your money where your mount is ~


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    MarcinM (01-10-2018)

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    Default Re: My motorised focuser for Astromaster 130

    Thank you guys for kind words
    Initially these 2 printed parts assembled together, were supposed to be printed as one, but due to "hard to remove supports" warning, I've split them in two. One of important things was to keep weight at minimum and have easy access to components, Astromaster 130 is relatively small. Otherwise I could design fully closed enclosure.
    To be honest these ABS prints aren't the best quality, pulley wheel and motor mount warped on few tries, printed at 100u resolution, not sure about infill. And I didn't print them myself, but used 3dhubs.com website. I don't feel in need for own 3d printer yet But after all I have these parts printed again in PLA, free of charge, been told they came out much better, should be with me tomorrow. I think I'll replace just the pulley and keep the rest as is.
    Regards
    Marcin
    AsteroidsRock likes this.

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    Default Re: My motorised focuser for Astromaster 130

    Micke187, I thought about nema motor in first place, but then realised how heavy they are, nema11 or 8 could do the job, but they are hard to find in UK or if anyone sells them, price is way too high. It seems that this cheap £5 stepper has more than enough torque and it's very light.
    UlteriorModem, these prints were done on TAZ 5 or TAZ 6, according to local hub info on their page.
    As last word I'd say I'm actually surprised that my measurements done before designing 3d models were perfect and everything fits together as planned lol.

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    Default Re : Re: My motorised focuser for Astromaster 130

    Hello MarcinM

    Ingenious solution to the focuser.

    I too have an Astromaster 130 and need to replace the focuser, the rubbish plastic rake has broken mainly due to me over tightening the screws and trying to line the tube with felt strips to stop the slop. epic fail. Anyway to the point and may i be so bold to ask, do you/would you consider assembling one (im no good with elec's etc) if so how much please?

    I do appreciate this is a bit bold of me to ask and if its inappropriate please ignore this and my apologies to you.

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    Default Re: My motorised focuser for Astromaster 130

    MarcinM has not been on forum in almost two years,
    The membership here has moved to www.theskysearchers.com as this site is no longer maintained.
    Feel free to join us and maybe someone has a solution that will help you.
    Refractors: Antares 105 f/15, Celestron 150 f/8, Stellarvue NHNG 80 f/6.9, TAL 100RS f/10, TS 102 f/11, UR 70 f/10, Vixen SD115s f/7.7
    Mounts: Celestron SLT w/ pier mod & EQ-3 tripod, Celestron hypertuned CG-5 w/ tracking motor & Argo Navis, Manfrotto 028B w/ Stellarvue M2C, Manfrotto 055PRO w/ 128RC, TAL-1 HD EQ, Vixen SXP w/ HAL-130 SXG & half pier
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    Amici prism, 2" Stellarvue Dielectric, 2" TeleVue Everbrite
    Eyepieces: A-Z

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    The weakest link in the optical chain is the large nut located directly behind the eyepiece/ camera. - Gabrielle
    Ya gotta keep this Apo/
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