Mirror Milestone

Well it’s been awhile, I know, and the last time I posted I had been polishing for a considerable amount of time. In fact I had already had at least 9 hours of time on the machine polishing with 30 to 45 minutes periods. Keep in mind for each one of these, the mirror has to be carefully cleaned and the lap is wire brushed and rinsed thoroughly. Then pressed for an hour or so. As previously mentioned, cleanliness is critical to avoid scratching with any contamination that could find its way between the lap and mirror. I had mentioned the mirror surface being hazy along an area near the edge. Doing some research, I found this is likely due to not having the lap in the ideal location in relation to the mirror on the fixed post machine. Typically, it is best to have the position of the lap overhang the mirror by 1/6 the diameter of the mirror. With my mirror being 16 inches and the lap being 12 inches in diameter, ┬áthis equates to the lap overhanging the mirror by 2.66 inches. Most of my polishing was done with the lap overhanging the mirror by 2.00 inches. No damage was done, and the spherometer showed I was still achieving a good curve with this adjustment. But after adjusting the lap position, andIMG_0201polishing for a few more sessions at 30 to 45 minutes each, improvements were immediately noticeable. In fact after performing another set of laser tests, all the way to the edge, there was no evidence of haziness and the laser was visible at the bottom of the mirror, indicating a clear highly polished surface on top. After one more session of 30 minutes, I declared the machine polishing operation complete! Rinsing the mirror and observing with an off axis image from sun reflection, brings out any fine scratches which are not visible any other way. But this is a tricking and dangerous task, because the mirror is already highly reflective, not a parabola by any means, but directly shining into eyes for any length of time is damage the retina! SO DO NOT DO THIS WITH CHILDREN PRESENT OR CURIOUS. this task is best done briefly and away from these conditions, best place I have found is on lawn in back yard. Fortunately for me I snapped this image when the sky was somewhat cloudy, and still able to achieve results without this risk. The mirror will now be put on the test stand and initial evaluation of the surface and the curvature will be made to determine if additional polishing is required or what strategy I will use to begin the figuring process. Thanks again and stay tuned!!IMG_0023

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