The Fan on Leo I Revealed

The unidentified fan on bottom edge of the image of Leo I has really simple explanation! Rays are diffraction patterns of Regulus lying twenty arc minutes bellow Leo I. The connection has been revealed by readers of IAN.cz. Thank you very much! It is a very good example how Internet can help expand of a knowledge. I have no explanation how I had ignored this fact. I inspected the position of Leo I with Xephem and I miss the critical proximity and I had in mind that the Leo I falls to the head of Leo. So don't forget look under legs when you are watching of the sky...

When I play with raw images, I inspect ones by an animation. The animation (warning 36M!) shows "a shut of the fan" near of its end so I gather from the investigation that the light pollution is due of a Earth's source. The animation shows a relative motion of the telescope (corrected by pointing), an airplane, cosmic-ray event and inner lights of our dome.


A last step to full explanation of the secret has been done by exebece. It take note that all stars are fainter at the end of the observation run. The instrumental magnitudes of the star UCAC2 36118678 shows rapid fall of its light fluxes. An explanation of the fainting is direct. The aperture of the telescope, controlled by the siderical motion, has been occult by our dome. A creativity of all possible mistakes by me is unbelievable...;)