How to Pick the Proper Telescope Eyepiece: A Beginner’s Guide

Introduction

Choosing the right eyepiece can feel overwhelming when you're starting out. Your telescope probably came with one or two basic eyepieces, but which ones should you add to your collection? How do focal length, magnification, and field of view actually work together?

This beginner-friendly guide explains exactly what you need to know to choose eyepieces that match your telescope and observing goals—without wasting money on the wrong ones.

Understanding Eyepiece Basics

What Eyepieces Do

Eyepieces magnify the image created by your telescope's primary optics. Unlike the telescope itself (which has fixed focal length), eyepieces are interchangeable, allowing you to change magnification simply by swapping eyepieces.

Key Specifications

Focal Length (mm)

The number printed on every eyepiece (6mm, 10mm, 25mm, etc.) is its focal length. This determines magnification when paired with your telescope:

Magnification = Telescope Focal Length ÷ Eyepiece Focal Length

Examples:

• 700mm telescope ÷ 25mm eyepiece = 28x magnification (low power, wide views)
• 700mm telescope ÷ 10mm eyepiece = 70x magnification (medium power)
• 700mm telescope ÷ 6mm eyepiece = 117x magnification (high power for planets)

Apparent Field of View (AFOV)

Measured in degrees, AFOV describes how wide the view appears when you look through the eyepiece. Common ranges:

• 40-50° – Standard (like looking through a tunnel)
• 60-70° – Wide-angle (more immersive, easier to observe)
• 80-100° – Ultra-wide (premium eyepieces, "spacewalk" effect)

Wider fields of view make it easier to locate objects and keep them centered as Earth rotates.

Barrel Size

Eyepieces come in two standard sizes:

• 1.25" (31.7mm) – Most common, fits nearly all beginner and intermediate telescopes
• 2" (50.8mm) – Larger barrel for wider fields of view, typically used with longer focal length eyepieces (25mm+)

Check your telescope's focuser to determine which size it accepts. Most accept 1.25", while many also accept 2" with an adapter.

Choosing Magnification for Different Targets

Low Power (25-40mm eyepieces)

Best for:

• Finding and centering objects
• Large star clusters (Pleiades, Beehive Cluster)
• Wide Milky Way sweeps
• Full Moon views
• Comets

Recommended: Vixen NPL 25mm Eyepiece ES39207 – 1.25″ Plössl Eyepiece

Medium Power (10-15mm eyepieces)

Best for:

• Lunar craters and features
• Bright galaxies (Andromeda, M81/M82)
• Nebulae (Orion Nebula, Ring Nebula)
• Double stars
• General-purpose observing

Recommended: SVBONY 68° Wide Angle 15mm for excellent field of view

High Power (6-8mm eyepieces)

Best for:

• Planetary details (Jupiter's bands, Saturn's rings, Mars' polar caps)
• Lunar close-ups
• Tight double stars
• Small planetary nebulae

Important: Only use high power on nights with steady atmospheric conditions (good "seeing"). Poor seeing makes high magnification views blurry and frustrating.

Recommended: Vixen NPL6mm Eyepiece ES39202 – 1.25″ Plössl 6 mm

Maximum Useful Magnification

Your telescope has a maximum useful magnification limit determined by its aperture:

Rule of thumb: 50x per inch of aperture (or 2x per millimeter)

Examples:

• 4-inch (102mm) telescope: ~200x maximum
• 6-inch (150mm) telescope: ~300x maximum
• 8-inch (203mm) telescope: ~400x maximum

Beyond this limit, you're just magnifying blur without revealing additional detail—called "empty magnification." Atmospheric turbulence typically limits practical magnification to 150-250x on most nights, regardless of aperture.

Eyepiece Designs Explained

Plossl (Most Popular for Beginners)

Characteristics:

• 4-element design
• 40-52° apparent field of view
• Excellent image quality
• Affordable
• Comfortable eye relief in longer focal lengths

Best for: Budget-conscious beginners building a versatile eyepiece collection

Available: Vixen NPL 8mm Eyepiece ES39203 – 1.25″ High-Power Plössl Eyepiece

Wide-Angle (60-70° AFOV)

Characteristics:

• More immersive viewing experience
• Easier to keep objects centered
• Better for tracking without motorized mounts
• Slightly more expensive than Plossls

Best for: Observers who want more comfortable, immersive views

Available: SVBONY 68° Wide Angle 15mm

Zoom Eyepieces

Characteristics:

• Variable focal length in one eyepiece (e.g., 7-21mm)
• Convenient for quickly adjusting magnification
• Eliminates need to swap eyepieces
• Narrower field of view than fixed focal length eyepieces

Best for: Beginners who want flexibility without carrying multiple eyepieces

Available: SVBONY SV135 7-21mm Zoom Eyepiece

Building Your Eyepiece Collection

Essential 3-Eyepiece Setup (Budget: $100-150)

1. Low power (25-32mm) – For finding objects and wide views
2. Medium power (10-15mm) – All-purpose observing
3. High power (6-8mm) – Planetary details on good nights

This covers 90% of observing situations and provides magnification flexibility for any target.

Alternative: Single Zoom Eyepiece (Budget: $50-80)

A quality zoom eyepiece like the SVBONY SV135 (7-21mm) covers medium to high magnification in one package—perfect for beginners who want simplicity.

Expanding Your Collection

As you gain experience, consider adding:

• Ultra-wide eyepiece – For immersive deep-sky views
• Specialty eyepieces – For specific targets (planetary, deep-sky)
• 2" eyepieces – For maximum field of view at low power (if your telescope accepts them)

Using Barlow Lenses to Multiply Your Collection

A Barlow lens multiplies your eyepiece's magnification (typically 2x or 3x), effectively doubling your eyepiece collection:

Example with 2x Barlow:

• 25mm eyepiece becomes 12.5mm (2x magnification)
• 10mm eyepiece becomes 5mm (4x magnification)

Advantages:

• Cost-effective way to add magnification options
• Increases eye relief at high magnification
• Quality Barlows maintain image sharpness

Disadvantages:

• Adds an extra optical element (potential for reduced contrast)
• Cheap Barlows degrade image quality—invest in quality

Recommended: Vixen 2X Barlow Lens 

Accessories to Enhance Your Eyepieces

Moon Filters

The Moon is extremely bright through a telescope, causing eye strain and washing out subtle details. A moon filter reduces glare and improves contrast, revealing more lunar features comfortably.

Color Filters (Planetary Observing)

Color filters enhance contrast on planets, making subtle features more visible:

• Red/Orange – Enhances Mars surface features and Jupiter's Great Red Spot
• Blue – Improves Saturn's cloud bands and Venus details
• Green – Enhances polar ice caps on Mars

Available: SVBONY SV227 SHO Narrowband Filter Set 5 nm 1.25" (H-Alpha / OIII / SII)

Eyepiece Storage

Protect your growing eyepiece collection with a quality storage case that keeps optics safe from dust, moisture, and impacts.

Common Beginner Mistakes to Avoid

Buying Too Many Eyepieces Too Soon

Start with 2-3 quality eyepieces covering low, medium, and high power. Learn what you actually use before expanding your collection.

Prioritizing Magnification Over Quality

A quality 10mm eyepiece will outperform a cheap 6mm eyepiece every time. Invest in good optics rather than chasing maximum magnification.

Ignoring Eye Relief

Eye relief is the distance between the eyepiece lens and your eye. Short eye relief (under 10mm) is uncomfortable, especially if you wear glasses. Look for eyepieces with at least 15mm eye relief for comfortable viewing.

Buying Incompatible Barrel Sizes

Always check your telescope's focuser size before buying eyepieces. Most beginner telescopes accept 1.25" eyepieces; some also accept 2" with an adapter.

Quick Eyepiece Selection Guide

For Your First Eyepiece Purchase:

If your telescope came with only one eyepiece: Add a complementary focal length. If you have a 25mm, add a 10mm for medium power.

If you want maximum versatility: Get a zoom eyepiece (7-21mm range)

If you want the best value: Buy a Plossl eyepiece

By Observing Interest:

• Planetary observers: Focus on 6-10mm eyepieces with good eye relief
• Deep-sky observers: Prioritize wide-angle eyepieces (15-25mm) with large apparent fields
• Lunar observers: Get a medium power eyepiece (10-15mm) plus a moon filter

Conclusion

Choosing the right eyepieces doesn't have to be complicated. By understanding focal length and magnification, matching eyepieces to your observing targets, starting with a versatile 3-eyepiece collection (or quality zoom eyepiece), and avoiding common mistakes, you'll build a collection that enhances every observing session.

Remember: quality matters more than quantity. Three excellent eyepieces will serve you better than a dozen mediocre ones. Start with the basics, learn what you enjoy observing, and expand your collection as your interests develop.

Telescope Wolves offers carefully selected telescope eyepieces and accessories from trusted brands like SVBONY and Vixen, helping you get the most from every night under the stars.

Clear skies and sharp views!