Eyepiece Selection Guide
What This Guide Tells You
Choosing the right eyepieces for your telescope can be overwhelming. This guide calculates recommended eyepiece focal lengths for different viewing purposes based on your specific telescope, helping you build a well-rounded collection.
Your Telescope
Recommended Starter Set
These three eyepieces cover most viewing needs and make an excellent starting collection:
Large clusters, extended nebulae, Milky Way
Globular clusters, smaller nebulae, galaxies
Planetary detail, double stars, lunar detail
Complete Eyepiece Range
| Purpose | Eyepiece | Mag | Exit Pupil | Best For |
|---|---|---|---|---|
| Finder / Widest Field | 42mm | 29x | 7.0mm | Finding objects, scanning, rich star fields |
| Low Power | 30mm | 40x | 5.0mm | Large clusters, extended nebulae, Milky Way |
| Medium-Low Power | 18mm | 67x | 3.0mm | Most deep sky objects, general viewing |
| Medium Power | 12mm | 100x | 2.0mm | Globular clusters, smaller nebulae, galaxies |
| Medium-High Power | 6mm | 200x | 1.0mm | Planetary nebulae, lunar overview, planets |
| High Power | 4mm | 300x | 0.7mm | Planetary detail, double stars, lunar detail |
| Maximum Power | 3mm | 400x | 0.5mm | Splitting close doubles, best seeing nights only |
Eyepiece Selection Tips
- Start with 3-4 eyepieces - Cover low, medium, and high power. Add specialty eyepieces later as you learn what you observe most.
- Invest in quality - A few good eyepieces outperform many cheap ones. You'll keep eyepieces even when you upgrade telescopes.
- Consider a Barlow lens - A 2x Barlow effectively doubles your eyepiece collection by providing additional magnifications.
- Match AFOV to your preferences - 52° Plössls are affordable; 68-82° wide-fields are more immersive but cost more.
Eyepiece Types to Consider
Plössl (50-52° AFOV)
Affordable entry point with good optical quality. Eye relief can be tight in short focal lengths. Best for mid-range focal lengths.
Wide-Field (65-72° AFOV)
More immersive views with better eye relief. Good value for quality and a popular all-around choice.
Ultra-Wide (80-84° AFOV)
Provides "spacewalk" experience. Excellent for deep sky viewing with great eye relief, but at a premium price point.
Zoom Eyepieces
Multiple focal lengths in one eyepiece. Convenient for travel with some optical compromise. Good for beginners exploring magnification ranges.
f-Ratio Considerations
Your telescope is f/6.0, which is considered moderate.
- Fast scopes (f/4-f/5): Require quality eyepieces to avoid edge distortion. May need coma corrector. Short focal length eyepieces have tiny exit pupils.
- Moderate scopes (f/6-f/8): Most forgiving. Wide range of eyepieces work well.
- Slow scopes (f/10+): Any eyepiece type works. May need longer focal length eyepieces for wide-field views.
Common Mistakes & Misconceptions
- "I need every focal length" - Start with well-spaced focal lengths. Too many similar eyepieces is wasteful.
- "Cheap eyepiece sets are a good deal" - Often includes useless focal lengths and poor quality optics. Buy fewer, better eyepieces.
- "Short focal length = high power" - True, but unusably short eyepieces (<5mm) are uncomfortable with tight eye relief.
- "Same eyepiece, same view on all scopes" - A 25mm gives different magnification on different telescopes. Calculate for your scope.
Related Calculators
- Telescope Magnification Calculator - Find magnification for any eyepiece
- Exit Pupil Calculator - Check if your eyepiece gives appropriate brightness
- True Field of View Calculator - See how much sky each eyepiece shows