Telescope Exit Pupil Diameter mm
Computes telescope exit pupil in millimeters from objective diameter and current magnification.
resultado
—
Telescope Exit Pupil
The exit pupil is the width of the cone of light that leaves the eyepiece and lands in your eye. You work it out with exit pupil (mm) = objective aperture (mm) ÷ magnification. Take a 150 mm telescope running at 75×: its exit pupil comes to 150 ÷ 75 = 2.0 mm. Crank the magnification up and the exit pupil shrinks; back it off and the exit pupil swells.
Why care about this number? Because your own pupil opens to something like 5–7 mm once your eyes adapt to the dark, and that ceiling drops as you get older. When the exit pupil is wider than your eye’s pupil, part of the light you collected just spills past the edge and goes to waste. At the other end, a tiny exit pupil under about 0.7 mm marks the highest magnification still worth using; push beyond that and the image dims while floaters in your eye start showing up.
Applications
Observers reach for the exit pupil when matching an eyepiece to whatever they are pointing at. A 2–4 mm exit pupil handles most deep-sky and lunar work. Somewhere near 5–6 mm hands you the brightest image you can get on faint nebulae under truly dark skies. And 0.7–1 mm sits at the high-power end for planets and double stars.
FAQ
What is the ideal exit pupil? That comes down to your target, though 2–3 mm tends to be a comfortable, do-everything range for general observing.
Can the exit pupil be too large? It can. Once it goes past your dark-adapted eye pupil (about 7 mm) the surplus light gets clipped at the edge and effectively thrown away.
How does it relate to magnification? The two move in opposite directions. Double the magnification and, at the same aperture, the exit pupil drops by half.
Related Tools
Telescope Resolving Power Diameter mm
Computes telescope angular resolving power in arcseconds using Dawes limit formula.
Telescope Limiting Magnitude Diameter mm
Estimates visual limiting stellar magnitude of a telescope from objective diameter in millimeters.
Binocular Exit Pupil mm
Computes binocular exit pupil in millimeters from objective diameter and magnification.
Emergency Exit Width
Calculate the required width of an emergency exit, W = (population ÷ unit capacity) × 0.55, dividing the population to be discharged by the capacity of people per exit unit and multiplying by one unit's width (0.55 m). The result, in metres, sizes doors, corridors, stairs and ramps of escape routes by the exit-unit criterion of fire safety codes. The capacity per unit varies with the type of exit (door, stair, ramp) and the occupancy. Enter the population and the capacity per exit unit.
Evacuation Time
Estimate the evacuation time of a space, t = N ÷ (F × width), dividing the number of occupants N by the product of the specific people flow F (people per minute per metre) and the total exit width (m). The result, in minutes, is the movement time for everyone to pass through the exits — part of the total egress time used in escape route design and fire safety verification. Adequate exit widths and flows ensure evacuation occurs before conditions become untenable. Enter the number of occupants, the specific flow and the exit width.
Minimum Hamster Wheel Diameter by Species
Looks up the smallest safe running wheel for dwarf, Chinese and Syrian hamsters, 21, 25 and 28 cm, so the spine stays flat instead of arching.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.