Dear Avandonk,
The TEC140 APO F7 is a Aplanatic (don't know what it means) oil-spaced triplet with an ED glass in between, with 3545 (3.5-inch internal diameter) Feathertouch dual speed focuser. I add it Robo focus for finer focusing.
See TEC's website at :
http://tec.idcomm.com/tec_us/index.html
More on TEC scopes at :
http://groups.yahoo.com/group/tec-scopes/
Raymond