BUY A BARLOW LENS
Many entry-level telescopes are sold with a pair of eyepieces – typically 25mm and 10mm – offering two levels of magnification out of the box. With the addition of an inexpensive Barlow lens, you can increase the size of your eyepiece collection. A Barlow lens doubles the effective focal length of your telescope so that when it’s placed in front of the eyepiece it doubles the magnification factor. A 25mm eyepiece behaves like a 12.5mm eyepiece, so you can achieve twice as many different levels of magnification – and each new eyepiece you buy going forward also has twice the value. What’s more, many Barlow lenses also include a T2 type thread, designed to accept a T-ring, allowing a DSLR or a mirrorless digital camera to be connected directly to the telescope. Beware of cheap Barlow lenses offering more than 2x magnification, though, as they are often poor quality.