Choosing an Eyepiece

Your telescope's eyepiece plays a major role in determining how much of the night sky you see and how much magnification you achieve. Swapping eyepieces can completely change your observing experience, making them one of the most worthwhile telescope accessories you can buy.

How Eyepieces Work

Eyepieces are measured by their focal length in millimetres (mm).

  • Lower numbers (e.g. 5mm–10mm) provide higher magnification.

  • Higher numbers (e.g. 25mm–40mm) provide lower magnification and a wider field of view.

The ideal eyepiece depends on what you're observing and the telescope you're using.

Which Eyepiece Should I Use?

Low Magnification (25mm–40mm)

Perfect for:

  • Star clusters

  • Large nebulae

  • Finding objects

  • Sweeping the Milky Way

Medium Magnification (12mm–20mm)

Ideal for:

  • General observing

  • The Moon

  • Bright galaxies

  • Many deep-sky objects

High Magnification (4mm–10mm)

Best for:

  • Jupiter

  • Saturn

  • Mars

  • Lunar detail

  • Double stars

Eyepiece Sizes

Most modern telescopes use either:

  • 1.25" eyepieces

  • 2" eyepieces

Always check which size your telescope accepts before purchasing.

Our Advice

Rather than buying lots of inexpensive eyepieces, start with two or three high-quality options that cover low, medium and high magnification. A good eyepiece can dramatically improve your observing experience for many years.