Observer’s Challenge complete report:  

https://rogerivester.files.wordpress.com/2012/08/february-2012-observers-challenge-theta-orionis.pdf

Theta 1 “The Trapezium”

March 1977:  4 1/4-inch f/10 spherical mirror, Edmund Scientific reflector @ 80x – Beautiful view of all four primary stars.  I could never see the E star with this scope.

February 1993:  10-inch f/4.5 reflector (using 4-inch off-axis stop-down mask) @ 254x – Seeing fair to good.  Could see the “E” star, but not easy. 

12-22-95:  80-mm f/15 refractor – All four stars appear as a beautiful white.

12-23-95:  10-inch f/4.5 reflector @ 120x – Conditions and seeing not good. Could see only the four primary stars.

March 1997:  3.5-inch Maksutov @ 135x – Seeing good, could see four stars.  On one occasion, I thought that I could see the “E” star, but very difficult, using averted vision. 

12-26-99:  10-inch f/4.5 reflector @ 142x – Fair to good.  All six stars visible, E and F fairly easy. 

12-26-99: