Orion XT10 Conversion with WEMOS R32 ESP32 and CNC Shield + some questions


Hi together,
I just finished converting my Orion XT10 Dobsonian to a GOTO with OnStep. First of all thanks for this great piece of Software to everyone who is involved in this.
From mechanical point of view, I mostly copied John K.´s built: https://onstep.groups.io/g/main/message/13894
But had to redesign all 3D-Printed parts since I was able to slice his STLs.

Here are some photos of my build:

The Parts I used:
quantity part price/piece € link
2 NEMA17 Stepper with 100:1 Gearbox 32,02 https://www.ebay.de/itm/392172995039
2 TMC2130 6,82 https://www.ebay.de/itm/274430359012
1 GT2 Belt 9mm 1360mm 6,32 https://www.ebay.de/itm/283708953451
1 GT2 Belt 9mm 784mm 5,35 https://www.ebay.de/itm/283708953451
1 WEMOS R32 D1 ESP32 5,73 https://www.aliexpress.com/item/32920335664.html
1 CNC Shield V3 5,8 https://www.aliexpress.com/item/2044795124.html
  Sum 100,88  

Although so far I had no chance to use it outside everything seems to be working fine.
Nevertheless, after using it in conjunction with the Android App I´ve got some questions:


Home Position

  • ·         It seems that I have to start the controller with the telescope pointing at Alt 0° Az 180°, otherwise I will not be able to align and the limits will be all over the place
  • ·         This is very inconvenient for me since I have to loosen the belts in order to manually move the telescope
  • ·         Is there a way for OnStep to figure out the limits after the alignment? I meat after I pointed it at one star OnStep should be able to figure out at which angle its pointing

Infinite Azimuth

  • ·         The way my telescope is built it is able to rotate an infinite amount of times, but when I tell it to go from Az 350° to Az 10° it turns 340° instead of going the short path of only 20°
  • ·         Can I somehow configure OnStep to allow this?

Offset between OnStep and Stellarium

  • ·         When I tell OnStep to track eg Mars from the OnStep App and then switch to the Stellarium App the circle that shows where the telescope is point is slightly offset from Mars. When tell is to track Mars from Stellarium directly the circle is spot on
  • ·         Since its been only cloudy nights so far I was able tell which of the two apps is right
  • ·         Does anybody know this problem?


  • ·         The ESP32 has built in WIFI which is not used by OnStep so far
  • ·         Are the any plans to implement this or should I just get an ESP8266?

Many thanks and best regards

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