The cloudy appearance of the original plane mirror M1 near the IR source can be seen below (left mirror in first image) compared to a better mirror on the right. I decided to replace it with a 1/8 inch thick front surface mirror (Myriad Al 1st surface 2.5 inch square mirror cut to 2.25 x 2.5 inches) with a 1/4 inch thick plywood backing (left mirror in second image). The original mirror is on the right in the second image. 1/8 inch thick glass is easier to cut using a glass cutter compared to thicker pieces. I used a vise clamp to hold the mirror while breaking off a 1/4 inch section to make a 2.25 x 2.5 inch mirror which would fit into the clamps (second image) for mounting on the panel in front of the IR source (third image). See also page 2 inside view
