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Backyard Astronomy Basics

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Click on a square to see/animate detailed Clear Sky Chart maps for each Sky/Ground category.

​​Dean Memorial Observatory is located on the grounds of Marshall County's Green Castle Recreation Area. The observatory is surrounded on 3 sides by the Green Castle Recreation Area Bison enclosure. Watch for the Observatory and Bison Enclosure signs at the junction in the road inside the recreation area. Go straight ahead at the signs, follow the road as it meanders past the Trumpeter Swan enclosure, and then go up the hill to the observatory parking area.

Dean Memorial Observatory is maintained and operated by the AACI.

*  On the Bortle scale of light pollution interference the observatory site is a Bortle 4, Rural/Suburban transition site with a naked-eye limiting magnitude (NELM) of 6.1–6.5.For reference, city sky is typically Bortle 8 to Bortle 10 with a naked-eye limiting magnitude of 4.5 and less.

 Amateur Astronomers

       of Central Iowa

AACI is a non-profit astronomy club serving Marshalltown and surrounding central Iowa communities. AACI is for those that share an interest in astronomy, space, nature, and science. AACI strives to promote interest in astronomy, and to share opportunities for viewing the night sky at the club's Green Castle Recreation Area observing site.

You don't need to have a telescope, or even much knowledge of astronomy to be an AACI member. The club has a 6" Newtonian telescope club members can borrow.

Indeed, the main reason for the club is to pool and share our knowledge among club members and with the public at our warm weather public nights. Many AACI members are families and children of all ages are very welcome.


AACI  monthly meetings are open to the public and are an excellent way to find out more about the club and to meet some club members. During the cold, snowy winter months the monthly meeting is held indoors at the Fisher Community Center in Marshalltown, Iowa

Monthly meetings start with an open to the public astronomy themed presentation of 45 or so minutes. Club business is then conducted after the presentation. Star-gazing begins once the club meeting ends - except in the winter.

By appointment, AACI also conducts private observing sessions for civic organizations and groups.