d "Dawes Limit." The formula for Dawes Limit is r = 4.56/D, where <I>r</I> is the separation (in arcseconds) of the closest resolvable double star, and <I>D</I> is the diameter of the objective in inches. Alternately, you can use r = 114/D, where <I>D</I> is the diameter of the objective in millimeters. And remember, Dawes Limit is only a guideline.<br><br>One reason for the popularity of double stars is that many of them show color. Colorful double stars are a joy to behold. It does take some time at the t