Adaptive Optics Near Infrared System (COME ON/COME ON+)

Developed by ESO and the Observatoire de Paris in 1993, ADONIS was the first “user friendly” Adaptive optic system (AO) attached to the ESO 3.6-m telescope at La Silla.

ADONIS is the evolution of the instruments COME ON and COME ON+. They were used to demonstrate that ground-based telescopes could correct for the distortions in the images caused by atmospheric turbulence. Moreover, this three-stage evolution instrument showed that a VLT AO system was feasible.

The idea behind the instrument was simple, but revolutionary in the 1980s: Real-time analysis and correction of the distortion of the stars. The information was obtained by ADONIS thanks to a series of lenslets. This lenslets were used to create individual stars images. The differences in each image were detected and compared. Then this data was used to control the shape of a small flexible mirror, which was moved by actuators — just like in active optics, another technology created by ESO. This movements applied to the small flexible mirror “neutralized” the distortion of the atmosphere.

At the beginning, COME ON had 19 actuators and performed corrections of the mirror 100 times per second. COME ON+ added more actuators (52) and doubled the speed of the corrections. The next step was a series of upgrades to the software and hardware, but for the developers the most important thing was to have a system with no specialist operator on site, and ADONIS achieved that goal.


This table lists the global capabilities of the instrument. The authoritative technical specifications as offered for astronomical observations are available from the Science Operations page.

Location: La Silla
Telescope: ESO 3.6-m telescope
Focus: Cassegrain
Type: Infrared imager
Wavelength range: 1–5 um
Spatial resolution: 8”
Spectral resolution:
First light: ESO
Science goal:

Solar System
Stellar Astronomy
Circum- and interstellar Matter

Images taken with the instrument: Link
Images of the instrument: Link
Press Releases with the instrument: Link
  • ESO
  • Observatoire de Paris