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Calcimator

Telescope Comparison Calculator

Compare two telescopes by f/ratio, light-gathering power, and angular resolution.

Inputs

Results

Light Gathering (A/B)

1.78×

Scope A f/ratio5.9
Scope B f/ratio4.9
Resolution A0.57 arcsec
Resolution B0.76 arcsec
How to Use This Calculator
  1. Enter Scope A Aperture (in), Scope A Focal Length (mm), and Scope B Aperture (in).
  2. Set Scope B Focal Length (mm).
  3. Review the Light Gathering (A/B) (×) result.
  4. Use Scope A f/ratio and Scope B f/ratio to inform your decision.
  5. Use the chart to visualize the results and explore different scenarios by adjusting inputs.

How the result changes with Scope B Aperture (in)

Scope B Aperture (in)Light Gathering (A/B)
4.92.67×
150.28×
260.09×
360.05×

What each input means

Scope A Aperture (in)
Primary mirror or lens diameter of telescope A in inches
Scope A Focal Length (mm)
Focal length of telescope A in millimeters
Scope B Aperture (in)
Primary mirror or lens diameter of telescope B in inches
Scope B Focal Length (mm)
Focal length of telescope B in millimeters

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Scope A Aperture (in) = 8, Scope A Focal Length (mm) = 1200, Scope B Aperture (in) = 6, Scope B Focal Length (mm) = 750 = 4 input(s) provided
  2. Calculate Light Gathering
    Light Gathering
    1.78 = 1.78
  3. Calculate Scope A f/ratio
    Scope A f/ratio
    5.9 = 5.9
  4. Calculate Scope B f/ratio
    Scope B f/ratio
    4.9 = 4.9

Engine last updated . Checked against 2 independently-derived tests — how we verify calculators.

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