in Roger Clarke's book, Visual Astronomy of the Deep Sky, he has a few maps of star clusters with magnitudes listed for the stars, so you can check the limiting magnitude of your telescope. My question is are these charts thought to be reliable? if not, where is a good source of magnitudes for stars within clusters? The example i was using the other night was NGC 6910, a loose cluster that is easy to find your faintest star and compare to his charts. I'm hoping his data is correct!
thanks for your help,