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Telescope Field of View Calculator

Calculate the angular field of view of telescopes and eyepiece combinations for astronomy observations

Calculate Telescope Field of View

×

Telescope-eyepiece magnification power

°

Angular diameter visible through eyepiece alone

Field of View Results

0.000°
Degrees
0.0'
Arc Minutes
0"
Arc Seconds

Field of View Area

0.000000 sq°

Total sky area visible

Moon Comparison

0.0 Moons

Moon diameters that fit (31' diameter)

Formula: FOV = Apparent FOV ÷ Magnification

Calculation: 0° ÷ 0.0× = 0.000°

Field of View Analysis

Field of View Quick Reference

Ultra-Wide (>4°)
Finder scopes, star clouds
Wide (2-4°)
Large nebulae, open clusters
Medium (1-2°)
Most deep-sky objects
Narrow (0.5-1°)
Planets, double stars
Very Narrow (<0.5°)
Planetary details, lunar

Common Object Angular Sizes

Sun/Moon~31'
Jupiter (max)50"
Saturn (max)20"
Mars (max)25"
Orion Nebula85' × 60'
Andromeda Galaxy3° × 1°
Pleiades110'

Observation Tips

🔭

Start with wide field eyepieces to locate objects

⭐

Use higher magnification for planetary details

🌌

Wide fields show nebulae and clusters best

🌙

Medium fields are ideal for lunar observation

✨

Exit pupil should match your eye's pupil

Understanding Telescope Field of View

What is Field of View?

The field of view (FOV) is the angular diameter of the observable portion of the sky visible through a telescope-eyepiece combination. It determines how much of the sky you can see at once and is crucial for planning observations.

Why Does It Matter?

  • •Determines which objects fit entirely in view
  • •Affects ease of finding and tracking objects
  • •Influences the observing experience and detail level
  • •Helps choose appropriate eyepieces for targets

Field of View Formula

FOV = Apparent FOV ÷ Magnification

FOV = Apparent FOV ÷ (ftelescope ÷ feyepiece)

  • FOV: True field of view (degrees)
  • Apparent FOV: Eyepiece's apparent field of view (degrees)
  • Magnification: Telescope focal length ÷ Eyepiece focal length
  • ftelescope: Telescope focal length (mm)
  • feyepiece: Eyepiece focal length (mm)

Note: Apparent FOV is marked on the eyepiece (typically 30°-110°) and represents the angular width you'd see looking through the eyepiece alone.

Telescope Types & Characteristics

Refractors

Use lenses to collect light. Excellent for planets and double stars.

Reflectors

Use mirrors to collect light. Great for deep-sky objects.

Schmidt-Cassegrain

Compact design with both lenses and mirrors. Versatile for all objects.

Eyepiece Types & Apparent FOV

Plössl: Good all-around52°
Kellner: Budget option45°
Orthoscopic: Sharp views45°
Wide Field: Comfortable viewing82°
Ultra Wide: Immersive experience110°

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