Fig.11 - The planetary nebula Messier 57 ("Ring nebula") in the constellation Lyra on October 2, 2011. Six 4 minute exposures at
ISO 1600 were added for this shot with the DeepSkyStacker software and the final image processing was done in Photoshop. My first
attempt with 8 minute exposures failed since the nebula already showed blown highlights. Equipment: Canon EOS 20Da camera, TeleVue
coma corrector, Zambuto 16" f/5 quartz optics in a Dieter Martini dobsonian telescope, dual-axis Tom Osypowski equatorial
platform, Lacerta MGEN autoguider, Teleskop-Service off axis system TS-OAG9 EOS.