Visualizing the maximum resolving power of current and future giant telescopes

On Firefox, if you get a "cannot access local images" popup, click it away and reload. The page should then work. I haven't been able to get this page to work on Chrome.

The wave nature of light sets a fundamental limit for the resolving power of any telescope. The minimum angle α that a telescope with aperture (diameter) d can resolve at wavelength λ is given by α = 1.22 λ / d . This angle is also known as the diffraction limit.

Most telescopes do not reach this maximum resolution for a variety of reasons. High-tech telescopes equipped with adaptive optics and space telescopes can come close to it though. That makes the diffraction limit a useful tool for getting a lower estimate of how big a telescope needs to be to achieve a desired resolution, and one that is 'almost' sharp for a no expenses spared adaptive optics or space telescope.

This javascript calculator lets you input an aperture (in meters) and a wavelength (in nm) and computes the corresponding diffraction limited angular resolution. It also (crudely) illustrates it by performing corresponding blur operations to show what various solar system targets (and two hypothetical exoplanets) would look like with that angular resolution from Earth. Base images are 800x800 and are limited to that resolution. Some of their viewing and illumination angles are not possible in a view from Earth.

Since the blur function used does not work correctly for blur radii > 180, even simulated 1-pixel resolution views show some detail.

Used images are: the 2010 LRO image of Tycho crater on the moon, Victoria crater on Mars imaged by HiRISE, a Galileo view of the Tiamat Sulcus region on Ganymede, a popular Cassini false-color mosaic of Enceladus (PIA06254), the Voyager 2 mosaic of Miranda (PIA01490), Voyager 2 views of Neptune and Triton, an artist's impression of Eris and self-made false color Jupiters and Neptunes to represent hypothetical exoplanets. I used Bj÷rn Jˇnsson's magnificent Jupiter and Neptune mosaics as sources.

You can enter wavelengths outside of the visible light spectrum, but the pictures will not change to represent appearance in non-visible wavelengths. The farther you stray from the visible spectrum, the more unrealistic results will get.

The exoplanet visualizations need to be taken with a grain of salt, or perhaps with two of them. Sufficient angular resolution is only one requirement for resolving surface features of an exoplanet. The others are enormous light gathering power (which interferometers typically lack, compared to a single mirror equal to the baseline), and a way to cancel out the glare of the many orders of magnitude brighter parent star. Even when technology has evolved to the point where optical interferometers with kilometer baselines are possible and economical, we may still not be able to see surface features on exoplanets.

Aperture in meters: Wavelength in nanometers:

Telescope Presets:

Here you can put in main mirror diameters and nominal wavelength for the Hubble Space Telescope, the James Webb Space Telescope, the Thirty Meter Telescope, the European Extremely Large Telescope, the (cancelled) Overwhelmingly Large Telescope and hypothetical but apparently achievable 1 and 7-kilometer baseline optical interferometers.

Object: Tycho Crater on the Moon

Image Width (km):
Distance (million km):
Resolution at distance (km)
Pixels across area:
Object: Victoria

Image Width (km):
Distance (million km):
Resolution at distance (km)
Pixels across the disk:
Object: Tiamat Sulcus on Ganymede

Image Width (km):
Distance (million km):
Resolution at distance (km)
Pixels across area:
Object: Enceladus

Image Width (km):
Distance (billion km):
Resolution at distance (km)
Pixels across the disk:
Object: Miranda

Image Width (km):
Distance (billion km):
Resolution at distance (km)
Pixels across the disk:
Object: Neptune

Image Width (km):
Distance (billion km):
Resolution at distance (km)
Pixels across the disk:
Object: Triton

Image Width (km):
Distance (billion km):
Resolution at distance (km)
Pixels across the disk:
Object: Eris
Base image credit:
ESO/L. Calšada and
Nick Risinger
(skysurvey.org)

Image Width (km):
Distance (billion km):
Resolution at distance (km)
Pixels across the disk:
Object: Hypothetical
exoplanet
with radius
200,000 km
at a distance
of 10 light
years

Image Width (km):
Distance (billion km):
Resolution at distance (km)
Pixels across the disk:
Object: Hypothetical
exoplanet
with radius
50,000 km
at a distance
of 100 light
years

Image Width (km):
Distance (billion km):
Resolution at distance (km)
Pixels across the disk:

Legal notices:

Jupiter and Neptune images ę 2014 Bj÷rn Jˇnsson, licensed and used under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.

Artist's impression of Eris ę 2011 ESO/L. Calšada and Nick Risinger, licensed and used under the terms of Creative Commons Attribution 3.0 Unported license

StackBlur javascript code ę 2010 Mario Klingemann, used under the terms of an informal attribution license.

All other work ę 2014 R. Boerner, Arizona State University School of Mathematical and Statistical Sciences, published under the intersection of the aforementioned licenses.