One formula · your inputs
Telescope magnification calculator
Magnification is the telescope focal length divided by the eyepiece focal length, then multiplied by any entered optical multiplier.
The number describes image scale only. It does not decide whether the atmosphere, aperture or optics can support that magnification.
Formula
How it is calculated
magnification = telescope focal length ÷ eyepiece focal length × multiplier- Use the telescope’s effective focal length.
- Enter the eyepiece focal length in the same unit.
- Set the multiplier to 1 when no Barlow or reducer is present.
What the result represents
A ratio of two focal lengths, with a separate user-entered multiplier.
The page keeps every decision-bearing quantity visible as an input. It does not look up a product catalogue, current market value or hidden recommended preset.
Limits of the model
The result is an idealised optical or geometric estimate from user-entered values. It does not model seeing, optical quality, central obstruction, transmission, distortion, focus error, tracking or sensor calibration.
Use the number to compare transparent scenarios. Verify critical observations, equipment combinations and coordinates independently.
Questions about this calculation
Does this magnification calculator choose equipment for me?
No. It evaluates only the displayed formula with the numbers you enter and does not make a purchase, compatibility or safety decision.
Why can the observed result differ?
Real optics and observing conditions add obstructions, transmission losses, aberrations, seeing, focus and measurement uncertainty that are outside the arithmetic model.
Can I use the result for navigation or safety-critical work?
No. SkyClock tools are transparent planning estimates, not certified navigation, engineering or safety instruments.
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