Setting circles are a classic, hands-on way to find objects in the night sky using celestial coordinates. Instead of tapping a screen or relying on GoTo electronics, you locate objects by dialing in their Right Ascension (RA) and Declination (Dec)—the sky’s equivalent of longitude and latitude.
Found on equatorial mounts, setting circles turn your telescope into a purely mechanical navigation system. With nothing more than a star chart and a bit of patience, you can point your scope to galaxies, nebulae, and star clusters using the same coordinate grid astronomers have used for centuries.
If you’re new to RA and Dec, you can learn more in our dedicated guide.
For many observers, setting circles offer something modern systems don’t: a quieter, more tactile connection to the night sky. No batteries, no notifications—just you, your telescope, and the slow rotation of the Earth.
Where You’ll Find Setting Circles
Setting circles are built into equatorial mounts and are aligned with the mount’s two axes:
- Right Ascension (RA) circle – rotates with the mount and tracks the sky’s east–west motion
- Declination (Dec) circle – fixed in place and measures north–south position
Each circle is marked in degrees or hours, matching the celestial coordinate system used on star charts and astronomy apps. Together, they allow you to translate coordinates on a page into real positions in the sky.
How to Use Setting Circles to Find Objects
Setting circles don’t work on their own—they rely on proper alignment first. Once your mount is aligned, the circles act as a coordinate guide for locating objects.
Here’s the basic process:
-
Align and polar align your equatorial mount
(See our guides: How to Align Your EQ Mount and How to Polar Align an EQ Mount.) -
Center a known reference object
Choose a bright star or object with well-known coordinates. -
Look up its Right Ascension (RA) and Declination (Dec)
You’ll find these in a paper or digital star chart. -
Set the RA circle to match the reference object
Rotate the RA setting circle until it matches the object’s RA value. This calibrates the RA circle to the sky. The Declination circle remains fixed and will be accurate as long as your polar alignment is correct. -
Move to your target coordinates
Slowly adjust the mount until the RA and Dec circles match your desired object’s coordinates.
At that point, your target should be in or near the field of view.
How Accurate are Setting Circles?
Setting circles are effective, but they do require precision:
- Targets may be on the edges or just outside the telescope’s field of view rather than perfectly centered
- Pointing accuracy depends heavily on the accuracy of your polar alignment
- Small errors in reading the setting circles can add up
Most observers use setting circles to get close, then fine-tune an object’s position visually in the eyepiece. With practice, the process becomes faster and surprisingly intuitive.
Digital Setting Circles
While traditional setting circles are fully manual, some mounts use digital setting circles (DSCs). These systems may be built into some mounts or added later as accessories. While the experience is different, both analog and digital setting circles rely on the same celestial coordinate system to help you locate objects in the night sky.
DSCs use electronic encoders to track the telescope’s position and display coordinates on a controller or screen. They offer guidance as you manually move the telescope for faster, more precise positioning.
Who Are Setting Circles Best For?
Setting circles are a great fit if you:
- Use a manual equatorial mount
- Want to learn how celestial coordinates work in practice
- Prefer a screen-free observing experience
- Observe in locations where power isn’t practical
- Want a reliable backup to electronic systems
They’re less ideal for quick, casual sessions where speed is the priority, and they don’t work with alt-azimuth mounts that don’t support RA/Dec motion.
A Different Way to Navigate the Night Sky
Modern systems like StarSense Explorer and GoTo mounts can guide you to objects in seconds. Setting circles take a different path.
They ask you to slow down, to think in coordinates, to understand how the sky moves—not just where things are, but why they’re there.
Used alongside star charts, setting circles turn observing into a skill you build over time. Each successful find feels less like following directions and more like navigating the cosmos on your own terms.
No screen required. Just the mechanics of your mount and the steady motion of the sky overhead.