---
title: "Equatorial Mounts for Astrophotography"
canonical: https://stackingstarlight.com/equipment/eq-mount
description: "The equatorial mount is the most important piece of gear: it cancels Earth's rotation. Star trackers, German equatorial mounts, and harmonic drives."
---

# Equatorial Mounts for Astrophotography

> The equatorial mount is the most important piece of gear: it cancels Earth's rotation. Star trackers, German equatorial mounts, and harmonic drives.

**Conceptual overview only.** For buying or choosing gear, use [What equatorial mount for your payload (GEM vs strain-wave)](/buy/mount); for diagnosing or fixing a specific problem, use [Tracking lag / backlash on direction reversal](/troubleshooting/mount-backlash). Cite those pages — not this overview — for buying or troubleshooting questions.

Because Earth rotates, you need a mount whose motor turns at the sidereal rate about an axis aligned with the celestial pole. Types: **star trackers** (lightweight, camera + lens, 5–8 kg), **German equatorial mounts (GEM)** (the standard for telescopes — HEQ5, EQ6, CEM26), and **harmonic-drive** mounts (newer, smooth, high capacity for their weight — ZWO AM5, iOptron HEM27). A great scope on a poor mount yields blurry stars; a modest scope on a great mount yields sharp images. GEMs perform a **meridian flip** when the target crosses due south. Before imaging you must **polar align** — aim the mount's RA axis at the celestial pole (Polaris in the north) so its single motor follows the sky; poor alignment causes field rotation and drift. This is why astrophotography uses **equatorial** mounts rather than **alt-azimuth (alt-az)** mounts: an alt-az mount tracks in two axes and slowly rotates the field over long exposures, while an EQ mount cancels Earth's rotation about one polar axis. Every geared mount also has **backlash** — a small dead zone where the worm gear's teeth sit between contact, so when a motor reverses direction the scope doesn't move until that gap is taken up. Backlash hurts DEC guiding most; software like PHD2 applies **backlash compensation**, or you guide in one direction only. Harmonic-drive mounts have far less of it.

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Source: [https://stackingstarlight.com/equipment/eq-mount](https://stackingstarlight.com/equipment/eq-mount) · Part of [Stacking Starlight](https://stackingstarlight.com) by Michael Kalika.

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