Messier 44 The Beehive Cluster in the constellation of Cancer the Crab. This is what happens when you put a lens made for exposing photographic film on a CCD sensor. This happens with an adapted film camera lens to a digital camera or in this case to an astronomical CCD camera.
Mamiya 110 mm RZ lens used with this image. Typically the film lenses need to be stopped down to F/4 to F/5.6 to work with the digital cameras. A few of the camera manufacturers in the late 1990's started selling "Digital ready" lenses with their film cameras.
Film architecture is different as each of the sensitive film grains are floating in an emulsion so that light striking these can hit them at more wider angles. As with the CCD/CMOS sensors, the light cone has to hit it at a narrower angle as these pixel sensors are more like holes in the ground. The light cone if too wide could scatter around the rims of these holes and get into the adjacent sensors.
110 mm Mamiya RZ lens used with an SBIG ST-2000XM CCD camera. The F/2.8 - F/4 shots were 5 minutes each of the LRGB filters; the F/5.6 shot was 10 minutes each of LRGB filters, 5 minute sub exposures.
The camera setup here: flic.kr/p/C85pz2