Dalia and Antoine, I have a question about your excellent book, "The Messier Catalog Workbook." Under the discussion of the globular cluster M13, you stated that this is a great target for "beginner-grade DSLR cameras." Can you please explain what your definition of "beginner-grade" camera is? I have a Canon EOS Rebel T1i which dates back to 2009, it was given to me for free and has been collecting dust for years (not literally). I suspect it's not a great camera but I recently thought it might be good enough to get started with astrophotography, so I am going to try to use it. But I wonder if this camera falls into this category of beginner-grade? Thanks!