When it comes to galactic objects and clusters, the constellation Canis Major has a lot to offer. This constellation includes a variety of island universes; it even contains a stunning example of two colliding galaxies famously photographed by the Hubble Space Telescope.
Below is a lineup of a few of the galaxies and star clusters lurking within Canis Major. We have provided magnitude numbers in parentheses for telescope and binocular observers.
According to SUNY Stony Brook astronomer Aaron Evans' Internet article on magnitude: "Very bright objects have negative magnitudes. For example, Sirius, the brightest star of the celestial sphere, has an apparent magnitude of -1.4. The modern scale includes the Moon and the Sun; the full Moon has an apparent magnitude of -12.6 and the Sun has an apparent magnitude of -26.73. The Hubble Space Telescope has located stars with magnitudes of +30 at visible wavelengths and the Keck telescopes have located similarly faint stars in the infrared."
Here's a sampling of Canis Major's deep sky objects: Basel 11A (+8.2), Cr 121 (+2.6), Cr 132 (+3.6), Cr 140 (+3.5), Haffner 6 (+9.2), Haffner 8 (+9.1), M 41 (+4.5), NGC 2204 (+8.6), NGC 2243 (+9.4), NGC 2345 (+7.7), NGC 2354 (+6.5), NGC 2360 (+7.2), NGC 2362 (+4.1 naked eye in a very dark sky), NGC 2367 (+7.9), NGC 2374 (+8.0), NGC 2383 (+8.4), NGC 2384 (+7.4), NGC 2396 (+7.4), Ru 18 (+9.4) Ru 20 (+9.5), Tr 6 (+10.0).
Most observed of Canis Major's objects is the open cluster M41 (aka NGC 2287)-it's the only "M" or Charles Messier object in the constellation. M41 is located south of the star Sirius and is approximately 195 million years old. Most of M41's approximately 100 stars are aging from the main sequence growth stage to the red-giant stage. If you'd like to try your hand at deep-sky astrophotography, M41 is a good target; its red-giant stars provide rich colors with long-exposure photography.