Viewing Distance Calculator
How big does something look when it may be hundreds or thousands of
kilometers away? How far away before you can't see it at all?
This calculator determines the approximate angle that a distant object
occupies in your field of view. You can compare the angles for various
objects and try to determine when such an object would no longer be visible to
your naked eye.
The calculator returns two figures for subtended angle. One is based on
Distance being a line from the view to the edge of the object; the second is
based on Distance as a line from the viewer to the center of the target.
These values should be very similar if Distance is much greater than the width
of the object.
Usage Notes:
- Your browser needs to support JavaScript 1.5 for this form to work properly.
- At some ratios, one calculation or the other may return an
invalid number.
- A large distance:object-width ratio is also preferable because the
calculator treats the object as two dimensional; any deviation that such
treatment causes will be reduced as the distance to the object increases.
Some comparisons:
- The moon is 384,400 kilometers from Earth; its subtended angle is 0.5181
degrees.
- At 10 meters, a 2cm marble occupies 0.1146 degrees of your view; a 20m
diameter asteroid occupies the same subtended angle at a distance of 10
kilometers.
How well could you see a marble from 10 meters (33 feet) away?
- At 1000 kilometers, a 20m asteroid occupies 0.0011 degrees; a basketball
occupies the same subtended angle at a distance of 13 kilometers.
How well could you see a basketball from 13 kilometers (8 miles)
away?
Get
the equations