photo sharing and upload picture albums photo forums search pictures popular photos photography help login
Samir Kharusi | profile | all galleries >> Globular Cluster Messier 13 in Hercules tree view | thumbnails | slideshow

Globular Cluster Messier 13 in Hercules

This gallery looks at the Great Globular Cluster in Hercules, M13 using either a Canon 1Ds or a Canon 20D camera. The optics were either a Canon 600mm/4.0L IS lens with a Canon 2x tele-extender or a Celestron C14. Mount: Celestron CGE, unguided. I was having problems with my autoguider. An oft-asked question is, "Can the CGE image unguided?". The answer is indeed "Yes", at reasonable focal lengths. Certainly one-minute exposures at 1200mm focal length work quite well. The middle frames do a comparison of the Canon 600mm lens + 2x tele-extender on a 1Ds to a C14 (4125mm) on a 20D. Conclusion is that even 10 second exposures at 4000mm focal length are too long for the CGE to track precisely. The image scale at 0.32 arc-sec per pixel is also excessively ambitious for any reasonable expectation of seeing conditions. Nevertheless, I also attempted 15-second close-ups of Omega Centauri under awful light pollution; and a comparison to M13 at the same image scale is included.
Camera Lens M13
Camera Lens M13
M13crop
M13crop
M13_at_1200mm+4000mm Animation
M13_at_1200mm+4000mm Animation
1to1_crops  Animation
1to1_crops Animation
1.55arc-sec_per_screen-pixel
1.55arc-sec_per_screen-pixel
OmegaCentauri+M13
OmegaCentauri+M13
Sparkly M13
Sparkly M13
Twinkling M13
Twinkling M13