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For example, American baseball star Mark McGwire is widely reported to use contact lenses that improve his 20/500 vision to be better than 20/10 5.ĭistinguising details at 150ppd would require 20/8 vision. However, corrective eyewear can often achieve this level. Anecdotally, my eye doctor told me that in all of his 20+ years in practice he has only seen one person (a teenager) who measured at this level without glasses. The graph on page 489 of 1 shows that only one or two individuals in the 100+ of tested 17-18 year olds got close to this limit (shown as -0.3 logMAR). Seeing details at 120ppd is equal to "20/10" vision (or "6/3" in Europe). Visual acuity peaks at around 25 years old and then slowly declines, but even then the average 75 year old has better eyesight than 20/20. While visual acuity changes per person and over time, the average acuity in adults is about 1.6 times better than 20/20, roughly 20/15 vision, or 80ppd. This is defined as the "normal" visual acuity for adults, but it is actually not the average. "20/20" vision (or "6/6" in Europe) corresponds to being able to resolve details 1 arcminute in size, or 60 pixels per degree. limit of high contrast feature detection 4 limit of alignment detection (hyperacuity) 4Īpprox. Visual Density pixels per degree (ppd) at center (~ 123 at edge)Ģ0/10 vision practical upper limit of visual acuityĢ0/8 vision theoretical upper limit of visual acuity 3Ģ0/4 vision approx.Astronomical Distance Travel Time Calculator computes the time to travel to distant parts of space at different velocities.The perceived "visual density" of a screen-and thus the amount of anti-aliasing possibly needed to make computer graphics look convincing and smooth-is dependent on the pixel density of the screen (the "ppi") and the distance from the user's eyes.Īdjust values below to calculate the visual density, or select a different value to control and instead enter the desired ppd.Sun, Moon, planets, stars, Milky Way's Center and Edge, Andromeda Galaxy) Astronomical Distance Calculator provides the distance from the Earth to numerous astronomical bodies (e.g.Exoplanet Calculator contains formulas for studying planets outside of our Solar System.Astronomy Calculator contains basic formulas for a college level Introduction to Astronomy.Kepler's 3 rd Law Calc has Kepler's 3 rd law solved for each parameter.Distance from absolute and apparent magnitude.Blackbody Temperature from Peak Wavelength.Wavelength Shift from Wavelength and Speed.Velocity from shift in Wavelength and Unshifted Wavelength.Relative Luminosity from Relative Temperature and Size.Relative Temperature from Relative Size and Luminosity.Relative Size from Relative Temperature and Luminosity.

Mass of extra-solar planet from mass and velocity of star and velocity of planet.Mass of extra-solar planet from mass of star, radius of star orbit and radius of exoplanet orbit.(S) - size or diameter of astronomical object.(R) - separation distance between the two objects.The formula for the resolving power of a telescope is: The resolving power α in arc seconds of a telescope with diameter D in meters that is collecting light of wavelength λ in nanometers equals is given by this formula. The resolving power of a telescope is the angular distance between two stars that are just barely visible through the telescope as separate images. Resolving Power (α): The calculator returns the Resolving Power in arc seconds. INSTRUCTIONS: Choose units and enter the following: The Resolving Power of a Telescope calculator computes the angular distance between two stars on the limit of visibility for a telescope.