The 12- to 16-inch Dobs

Abstract

When making the transition from an 8-inch to a 10-inch or 12-inch aperture, portability is greatly sacrificed, but with the benefit of gaining more resolution and light-gathering power. The gain in brightness is always more profound than the gain in resolution. If you step away from an 8-inch Dob and place your eye at the focus of a 16-inch instrument, the first thing you’ll notice is how much more bright (4-fold) the objects have become. Only afterwards will you notice the smaller gain in resolution (2-fold). Deep sky objects that are mere suggestions in the 8-inch ‘scope come alive in the larger ‘scopes, allowing far greater detail to be discerned to the careful visual observer. The greater resolving powers make these ‘scopes killer performers on planets when conditions are right. There is a more dramatic difference in stepping up to a 10-inch Dob from an 8-inch model, compared with going to a 12-inch aperture from a 10-inch instrument. And it goes without saying that the move from 12 to 16 inches is sure to be immediately obvious to the eye. This chapter takes a look at the largest instruments commonly used by amateurs – those in the 12- to 16-inch aperture class. They offer huge light grasp and, when conditions allow, reveal the wonders of the universe in bright and stunning detail.