---
title: "Choosing a guiding setup: guide scope vs off-axis"
canonical: https://stackingstarlight.com/buy/guiding
description: "Autoguiding hardware is one real decision — a **separate guide scope** or an **off-axis guider (OAG)** — plus matching a guide camera to it. The right choice depends mostly on your imaging focal length."
---

# Choosing a guiding setup: guide scope vs off-axis

> Autoguiding hardware is one real decision — a **separate guide scope** or an **off-axis guider (OAG)** — plus matching a guide camera to it. The right choice depends mostly on your imaging focal length.

## 1. The decision driver: focal length

- **Short focal length (≲500–600 mm):** a small **guide scope** is simple, cheap, and easy to get a
  star — flexure is rarely an issue at these scales.
- **Longer focal length (≳700–800 mm):** an **OAG** picks the guide star off the main optic, so any
  flexure between two separate tubes can't creep in. At long FL, differential flexure is the usual
  cause of stubbornly high error, so the OAG earns its extra fiddliness.

| | Guide scope | OAG |
|---|---|---|
| Ease of finding a star | Easy | Harder (small pickoff field) |
| Flexure immunity | Lower | High |
| Setup fuss | Low | Higher |
| Best at | Short–mid FL | Long FL |

## 2. Match the guide camera

Pick a small-pixel mono guide camera; what matters is **guide resolution** (camera pixel size vs
guide focal length) landing in a sane range so the guider sees sub-pixel motion. With an OAG the
effective guide focal length is your main scope's, so a sensitive small-pixel camera helps find a
star in the small pickoff field.

## 3. For a ~700 mm imaging setup

This is the crossover: an OAG is the safer long-term choice (flexure-immune), paired with a sensitive
small-pixel guide camera. If you'd rather keep it simple and your mount/tube are stiff, a good guide
scope can still work — but flexure becomes the first suspect if error stays high.

## 4. Budget tiers (confirm current models)

- *Entry:* compact guide scope + small-pixel guide camera.
- *Mid:* OAG + sensitive guide camera for longer focal lengths.

## A heads-up for later

If guiding oscillates or won't settle after you've chosen hardware, that's usually tuning or flexure
— see [stabilizing autoguiding](/troubleshooting/guiding-phd2).

---

Why guiding is needed: [autoguiding basics](/equipment/guiding).

---

Source: [https://stackingstarlight.com/buy/guiding](https://stackingstarlight.com/buy/guiding) · Part of [Stacking Starlight](https://stackingstarlight.com) by Michael Kalika.

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