Jaegers 6" f/10 "GJD" OTA Construction - Main Tube & Lens Cell (alignment test fit)
 

Close-up photo of Rear Lens Cell aligned with drilled hole in Main Tube - 7 (Click to see an enlarged image.)

 
Test fit proved successful for lining up the holes to attach the rear lens cell to the main tube.

NOTE: Since this image can cause your brain to see an optical illusion, what you are looking at here is the inside flocked surface of the top section of the rear cell (left of center), slid onto the main tube to the right, which is showing its inside wall surface. In any case, all three (3) holes lined up perfectly.