Why You Should Build an Aperture Mask for your Celestron FirstScope.
An aperture mask is a simple cap you place over the telescope to cut down the aperture. The reasons why you might want to do this are not obvious, but in short, they cut down on optical aberrations significantly. This is especially important in a telescope with flawed optics--specifically those with spherical mirrors. This article will be about masking down a FirstScope, but the same principle could apply to any telescope with a spherical mirror, including telescopes that for the price have no right to have one, such as the deplorable PowerSeeker 127EQ and the AstroMaster 114EQ. The Celestron FirstScope is one of my favorite small telescopes, and it's pretty good for scanning around for bright DSOs, glancing at the Moon, etc. Its stock eyepieces are utter garbage, and when combined with the fast spherical mirror (76mm f/4), the Huygens 20mm is almost unusable.