Reflecting Telescope

NEVER point any telescope at the Sun without proper solar filters. Even brief exposure can cause permanent eye damage or blindness. Ensure telescopes are pointed only at safe terrestrial objects during demonstrations.

Never touch mirror surfaces directly. Oils from skin can permanently damage reflective coatings. If demonstrating mirror components, handle only by edges and use clean gloves.

Purpose

Compares Newtonian and Cassegrain reflecting telescope designs side-by-side. Students see how different secondary mirror configurations (flat diagonal vs. convex) redirect light to different eyepiece locations, and why reflectors avoid chromatic aberration.

Orion Newtonian reflector telescope with blue tube on a Dobsonian tabletop mount, focuser and eyepiece at the top of the tube

Meade Schmidt-Cassegrain telescope with blue tube on a fork alt-azimuth mount with setting circles, corrector plate visible at front, eyepiece at rear

Inverted and magnified view of a clock face through the telescope eyepiece, showing the numbers 12 and 1 upside-down

Figure 1: Newtonian reflector (Orion) on a Dobsonian alt-azimuth mount. The eyepiece is at the top side of the tube, where a flat diagonal secondary mirror redirects light 90° from the primary.

Figure 2: Schmidt-Cassegrain reflector (Meade) on a fork mount with setting circles. The eyepiece is at the rear — light reflects off the primary, bounces off a convex secondary, and passes back through a hole in the primary.

Figure 3: Magnified view of a wall clock through the telescope. The image is inverted, as expected for an astronomical telescope. Point a video camera into the eyepiece to display this to the class.

Danger: Never Point at the Sun

Warning: Handling Optical Surfaces

Purpose

Safety Warnings

Danger: Never Point at the Sun

Warning: Handling Optical Surfaces

Purpose