Originally Posted by geo1

Ajo,
Was looking to see what I owed and reviewed your Darkfield stop filter.
Looks good. A hint: I bought a $9 compass with a knife attached which allows me to mark and cut simultaneously. Worked cool when making color filters from colored plastic sheets. Also, consider using thread glued in a cross pattern on the center circle and a drop of glue on the thread on the outer circle to hold it in place.