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leo-john233/diy-harmonic-equatorial-mount

Analysis updated 2026-05-18

★ 15HTMLAudience · generalComplexity · 5/5LicenseSetup · hard

TLDR

Open-source hardware and firmware plans for a DIY harmonic-drive equatorial telescope mount using OnStep firmware on an ESP32.

Mindmap

mindmap
  root((repo))
    What it does
      Equatorial mount design
      Star tracking
      Custom PCB
    Tech stack
      ESP32
      OnStepX
      Custom PCB
    Use cases
      Astrophotography
      Connect to ASCOM INDI
      Lightweight build
    Audience
      Amateur astronomers

Code map

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What do people build with it?

USE CASE 1

Build a lightweight harmonic-drive equatorial mount as a cheaper alternative to commercial options.

USE CASE 2

Track stars accurately for astrophotography using OnStep/OnStepX firmware on ESP32.

USE CASE 3

Connect the mount to astronomy software like N.I.N.A., INDI, or ASCOM over WiFi, Bluetooth, or USB.

USE CASE 4

Machine and assemble a custom PCB with stepper drivers for precise, backlash-free tracking.

What is it built with?

ESP32-WROOM-32EOnStep/OnStepXC++Custom PCB

How does it compare?

leo-john233/diy-harmonic-equatorial-mountadguardteam/dns-sde-extensionaiecosvietnam/aiecos-social-crm
Stars151515
LanguageHTMLHTMLHTML
Last pushed—2025-01-09—
Maintenance—Stale—
Setup difficultyhardmoderatemoderate
Complexity5/52/53/5
Audiencegeneraldeveloperpm founder

Figures from each repo's GitHub metadata at analysis time.

How do you get it running?

Difficulty · hard Time to first run · 1day+

Requires machining and PCB assembly, documentation is written in Chinese.

Software is licensed under GPL-3.0 and hardware under CERN-OHL-S v2, both open licenses requiring derivative works to stay open.

In plain English

Leo-John233/DIY-Harmonic-Equatorial-Mount is an open-source hardware and software project for building a DIY harmonic equatorial mount for amateur astronomy. The description explains it was created because the author found the EQ3D equatorial mount too heavy to carry repeatedly, and commercial harmonic mounts cost too much relative to this DIY version's specifications. An equatorial mount is a type of telescope support that rotates around an axis aligned with Earth's rotation, allowing it to track stars smoothly as the sky moves. A harmonic drive reducer is a compact, high-ratio gear mechanism that provides precise, backlash-free motion, well suited for astronomy tracking. This design uses a GEM (German Equatorial Mount) configuration, driven by a 25-100 harmonic reducer combined with belt drive and a 42-stepper motor. The control system runs OnStep/OnStepX firmware on an ESP32-WROOM-32E microcontroller, which is the widely used open-source telescope controller platform. The electronics include a custom PCB with TMC series stepper motor drivers (compatible with both TMC2209 and TMC5160), Wi-Fi via an ESP07S module, Bluetooth, USB-B, and an integrated DS3231SN real-time clock chip. The mount connects to popular astronomy software including N.I.N.A., INDI, and ASCOM over Wi-Fi, Bluetooth, or USB. The README states the design achieves arc-second level RMS tracking accuracy without needing a counterweight for loads up to 20-25 kg. The estimated total build cost is approximately 2500 RMB, with machined parts under 1500 RMB. The README is written in Chinese. Software is licensed under GPL-3.0 and hardware under CERN-OHL-S v2.

Copy-paste prompts

Prompt 1
Explain how a harmonic drive reducer improves tracking accuracy compared to a standard EQ3D mount.
Prompt 2
Help me set up OnStepX firmware on an ESP32-WROOM-32E for this equatorial mount design.
Prompt 3
Walk me through connecting this mount to ASCOM or INDI astronomy software over WiFi.
Prompt 4
Estimate the total cost and parts list for building this harmonic equatorial mount.

Frequently asked questions

What is diy-harmonic-equatorial-mount?

Open-source hardware and firmware plans for a DIY harmonic-drive equatorial telescope mount using OnStep firmware on an ESP32.

What language is diy-harmonic-equatorial-mount written in?

Mainly HTML. The stack also includes ESP32-WROOM-32E, OnStep/OnStepX, C++.

What license does diy-harmonic-equatorial-mount use?

Software is licensed under GPL-3.0 and hardware under CERN-OHL-S v2, both open licenses requiring derivative works to stay open.

How hard is diy-harmonic-equatorial-mount to set up?

Setup difficulty is rated hard, with roughly 1day+ to a first successful run.

Who is diy-harmonic-equatorial-mount for?

Mainly general.

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