How to Choose Eyepieces for Your Astronomy Telescope
- 1. Overview
- 2. Essential Eyepiece Specifications
- 2.1 Focal Length
- 2.2. Apparent and True Field of View
- 2.3 Barrel Size and Field Stop
- 2.4 Exit Pupil
- 2.5 Eye Relief
- 3. Key Considerations for Choosing an Eyepiece
- 3.1 Maximum, Minimum, and "Optimum" Magnifications
- 3.2 Telescope Focal Ratio
- 3.3 Observing Interests and Personal Preference
- 3.4 Price
- 4. Choosing Eyepieces for Your Telescope
- 4.1 Case Study 1 -- Choosing Eyepieces for a 4" ED/Apochromatic f/7 Refractor
- 4.2 Case Study 2 -- Choosing Eyepieces for an 8" f/10 Schmidt-Cassegrain Telescope
- 4.3 Case Study 3 -- Choosing Eyepieces for a 10" f/4.7 Dobsonian Telescope
- 4.4 A Word About Zoom Eyepieces
- 5. Summary
- 6. References
Figure 1 – Eyepieces for astronomical telescopes. From left to right, the Starguider 25mm eyepiece, Nikon 17.5mm 72-degree eyepiece, 9mm Nagler eyepiece, and the Explore