How to estimate distance by a telescope

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Discussion Overview

The discussion revolves around the methods of estimating distance to a target object using telescopes, particularly in historical contexts such as sailing. Participants explore various calibration techniques and instruments that assist in distance estimation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant questions whether telescopes can be used to estimate distances and suggests that calibration is necessary for accurate measurements.
  • Another participant proposes that knowing the size of an object, combined with its apparent size through the telescope and the telescope's magnification, can help determine distance.
  • A third participant mentions the use of stadia marks in surveyors' theodolites, which provide a distance factor when viewing a ruler or staff, and references specialized instruments called tacheometers for distance measurement.
  • Another participant expresses interest in the mathematical curve that relates target viewing size to distance and requests information on how it is calculated.
  • One participant notes that some rifle scopes and golf scopes have calibrated reticles to assist in estimating distances based on known object sizes, although such scopes are not allowed in professional golf.

Areas of Agreement / Disagreement

Participants present multiple competing views and methods for estimating distance using telescopes, with no consensus reached on a single approach or technique.

Contextual Notes

Some discussions involve assumptions about object sizes and the specific calibration methods used, which may not be universally applicable across different types of telescopes or contexts.

zli034
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Guys

I don't know if people could estimate distance to a target object by looking through a telescope. I believe telescopes for this kind use must be calibrated some how. When the time people sailed in the ocean and when they spotted another boat by the telescope, how did they tell the distance?

thanks
 
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Well, if you know how big a boat is, and you know how big it looks in a telescope... combining that with the magnification of the telescope tells you how far away it is.

Maybe I'm unclear on what you're asking.
 
Some rifle scopes have calibrated reticles (typically with spacing conforming to the body size of a deer or similar) to help with aiming (elevation). Golfers have scopes calibrated to standard flag-pin heights so that golfers can estimate the distance to the hole and make their club selections. These are forbidden in pro golf so golfers have to rely on their caddies' notes and experience instead.
 

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