Calculadora de Relación Focal de Telescopio Gratis

Calcula la relación focal (f/) de tu telescopio para determinar brillo y campo de visión.

mm
mm

Focal Ratio

6.0 f/

Focal Ratio vs Focal Length

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Fórmula

Focal Ratio (f-Number)

f/# = Focal Length / Aperture

Lower f-numbers ("faster" scopes) collect light over a wider cone and are better for astrophotography of faint objects. Higher f-numbers ("slower") give longer focal lengths for planetary detail.

  • f/4 to f/5: fast, wide-field
  • f/8 to f/10: moderate, good all-round
  • f/12+: slow, high magnification

    • Ejemplo Resuelto

    1200 mm focal length, 200 mm aperture.

    1. 01f/# = 1200 / 200 = f/6
    2. 02This is a moderately fast scope, good for both visual and imaging.

    Preguntas Frecuentes

    Why does focal ratio matter for photography?

    Faster (lower f/#) means shorter exposure times for the same signal. An f/4 scope requires 1/4 the exposure of an f/8 for extended objects.

    Does focal ratio affect visual brightness?

    For point sources (stars), no - only aperture matters. For extended objects (nebulae), faster focal ratios give brighter images at the eyepiece.

    What is a typical focal ratio?

    Schmidt-Cassegrains are typically f/10. Newtonian reflectors range from f/4 to f/8. Refractors for astrophotography are often f/5 to f/7.

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