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The Ring Nebula M 57 (NGC 6720)

Date:13.04.1997 Time:1:15 UT Exposure:5 min
Field of View:7.4' x 5.0' Receiver:576 x 387 CCD Filter:IF501
Instrument: D=2m, f=5.6m Observatory: Pik Terskol, Caucasus Observer:T. Credner, T. Bonev, K. Jockers

© Copyright by the observers

Max-Planck-Institut für Aeronomie

Shown is the famous Ring Nebula M 57 of the northern constellation Lyra. It is a planetary nebula with a hot central star ionizing the surrounding gas. The image shows the light of the double ionized oxygen OIII at 501nm. The gas itself was probably blown off from the central star a long time ago.

More unknown are the weaker outer parts of this gas shell. On normal exposures just the bright inner ring is visible, but above you can also see the weak halo with structured loops. To visualize the faint and bright structures simultaneously, i.e. to stretch the visual dynamic range, a strong false color look-up table was taken together with a double logarithmic intensity scaling.