This may be a related question to Cliff's. I have been observing SU Cyg and use Tycho-2 2151-4816-1 as a comparison star. I have found discrepancies in the magnitude across different star chart programs.
Cartes du Ciel lists m=10.10 Meade's Auto Star lists m=9.54 C2A lists m= 11.443 Has anyone else noticed this? How is it possible that different values are reported for the same Tycho star? Robin Riordan
