I measured the diameter of the quartz DIS slit on the Solar Observatory's measuring engine. I measured the width of the slit at five points along its length. Here are the measurements. width (microns) width (arcsec) 170 1.00 168 0.99 177 1.04 178 1.05 178 1.05 [the scale at the focal plane is 0.00589 "/micron] From these measurements the average slit width is 1.03 arcsec, significantly narrower than the 1.5 arcsec we've been assuming. I also measured the width of the NMSU 2 arcsec acetate slit. The measured width is 2.13 arcsec. Here are a few words on the appearance of these two slits as viewed under the microscope. The quartz slit width is very non-uniform. The edges are noticably wavy under the microscope. There's a ragged notch in the edge at one location, and there are several small dark spots along the slit. The acetate slit has very uniform width but the under the microscope one can see that the "clear" portion of the acetate (the slit) has thousands of tiny colored flecks (or very tiny bubbles) embedded in it. -karen g. APO APO APO APO APO Apache Point Observatory 3.5m APO APO APO APO APO This is message 11 in the apo35-dis archive. You can find APO the archive on http://astro.princeton.edu:82/apo35-dis/INDEX.html APO To join/leave the list, send mail to apo35-request@astro.princeton.edu APO To post a message, mail it to apo35-dis@astro.princeton.edu APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO