Moravian instruments, Inc., source: https://www.gxccd.com/art?id=561&lang=409, printed: 23.5.2019 21:42:16
|M101 Pinwheel Galaxy in Ursa Major is angularly large object, but its surface brightness is rather low. This is why it is sometimes used by visual observers to judge sky brightness — if you can see M101, background sky is quite dark. But if you point you telescope exactly where M101 is located and cannot see any trace of it, the light pollution on your site is probably high and also the weather may not be cooperating.|
Low surface brightness is no obstacle for cooled astronomical camera, which can accumulate literally single photons for a long time. And digital processing of stacked long exposure images can reveal fantastic details, which can never be seen by eyes. Paolo De Salvatore used his G2-8300 CCD camera on 10” RC telescope to gather almost 12 hours of total exposure time of this galaxy. So, no wonder his image shows incredible details.