Ground-based Image of Comet Holmes - November 1, 2007 Caption The ground-based image of Comet 17P/Holmes was taken November 1, 2007, by astrophotographer Alan Dyer. The observations were made in southern Alberta, Canada with a 105mm apochromatic refractor at f/5 with a Canon 20Da camera at ISO400. Field is about 2.5 x 1.5 degrees. Credits NASA, ESA, and A. Dyer