This story is getting more and more mysterious : in the 1978 Tasco catalog is written, that the main mirror is a parabolic one. Yesterday I got a manual for the ( identic ? ) Mizar CX-150, and in this manual the mirror is described as a spheric one !! Strange !!
But anyway : the quality of this optics seems to be high class !

Kind regards, Michael

EDIT : I was totally wrong with the mirror and have to excuse me for the wrong rumours I launched here !!

I read the Tasco catalog again and in fact theres with no word mentioned, that the mirror is parabolic ! Maybe I was drunken ?!

In fact it is a spheric mirror, but a good one !!
I saw very good spheric mirrors in the russian reflectors by TAL - for example the TAL 1 ( 110/805 mm and the TAL 2M 150/1200 mm ).