By far the most important quality of a telescope is its optics. If the image is not sharp, no other qualities like a good and sturdy mount, expensive eyepieces, beautiful appearance or other features, though desirable, can compensate for it. Always choose a telescope which shows a crisp and well defined image at around a magnification 25 times its mirror aperture in inches. Importance wise, other features are: sturdy mounting; no vibrations, smooth movements on both axes. No backlash. Smooth focuser; adjustable cross wired finder telescope. Equatorial mount, setting circles…there is no end to features but these are more than sufficient a beginner should look for.