Photo of the Week for July 7, 2017
Summer is globular cluster season. One of the best known and brightest (the two are, after all, related) is M13 in Hercules. Many observers would agree that M13 is the most spectacular globular north of the celestial equator—but is it the finest visible from Canadian latitudes? A strong case could be made for M22 in Sagittarius, which shines at magnitude 5.2 compared with M13’s more modest magnitude 5.8. What do you think?
This photo of M13 by Nepean, Ontario, imager Oleg Bouevitch shows the cluster’s grandeur well. (The tiny smudge near the lower left edge of the frame is 15th magnitude galaxy IC4617.) Oleg used a Celestron EdgeHD 11 flat-field Schmidt-Cassegrain telescope (with a 0.7x reducer for an effective focal ratio of f/7) and Atik 383L+ CCD camera to acquire a total of 280 minutes imaging data shot through Astroden LRBG filters.