Amateur Astronomers

       of Central Iowa

Primary Mirror Diameter - 16 inches
Primary Mirror Thickness - 3 inches
Primary Mirror Weight - 50 pounds
Telescope/Mount Weight - 400 pounds
Telescope Focal Length - 84 inches (2134 mm)
Telescope Focal Ratio - f /5.3

The 16" Newtonian telescope is mounted on a concrete pier

that goes 45 inches into the ground to prevent it being moved by winter frost. The pier is also separate from the floor of the observatory so the telescope is isolated from floor vibrations caused by people moving about in the observatory.



Dean Memorial Observatory is named in memory of Don Dean, a founding member of the Central Iowa Astronomers (CIA) amateur astronomy club. Central Iowa Astronomers was founded in the 1950's.

Later the name of the club was changed to Amateur Astronomers of Central Iowa (AACI).

About 45 years ago the club acquired a 16" Pyrex telescope mirror blank. The blank sat around for several years while club members commiserated on what to do with it. Back then a 16" mirror blank was a really big mirror blank for an amateur astronomy club telescope.  

Three club members took action in the mid '70s.
Larry Watkins & Tom Hallam ground the flat Pyrex low-expansion glass surface to the paraboloid curve shape the 16" mirror blank needed to make it usable in a telescope. They did the hours, and hours, and hours(some 700 man-hours) of grinding by hand in Tom Hallam's basement.
Pat Malloy, with help from Larry Watkins, built the telescope's Serrurier truss framework, equatorial fork mount and motor drive (500 more man-hours of telescope construction).

Apparently, the telescope was the 3rd largest telescope in Iowa at that time.

In the mean time, the club got approval from the Marshall County Conservation Board to build an observatory at the then new, Marshall County Green Castle Recreation Area to house the big 16", f/4.5 Newton type telescope and motor driven tracking mount that was being constructed.

The observatory was built from scratch by members of the club, with contributions from many local civic organizations.

The 14 foot observatory dome is a modified grain silo top dome.