• Though it was engineered and constructed by Zeiss Optical Works before the days of computers, it was accurate enough to correct for Earth's precession, the slight wobble in its rotation that causes "true north" to change over time.

• It was in use for so long that parts were no longer available from Zeiss Optical, which had moved on to manufacturing Models III and IV after World War II. Instead, Buhl employees custom-made them.

• The elevator that brought the Zeiss from the Buhl basement to the Theater of the Stars operated on screw jacks, a special kind of lift that provided a very smooth ride so the lenses would not be damaged.

• The Zeiss, which went into operation at Buhl Planetarium in 1939, was re-assembled for the new exhibit at Carnegie Science Center on June 18 - its 71st "birthday."

That's Fascinating, where Mark Roth spotlights the odd and the interesting in everyday life, is featured exclusively in the Opinion section on PG+, a members-only web site from the Pittsburgh Post-Gazette. Our introduction to PG+ gives you all the details.