The University of Chicago

373 W. Geneva St, Williams Bay WI 53191 (Latitude 42 34.2, Longitude -88 33.4)
Look Through a Large Telescope at the Moon, Planets, Galaxies, the Milky Way, Nebulae, Star Clusters and More at Yerkes Observatory!

From season to season the evening sky changes slowly and reveals many different celestial wonders visible with, and without, optical aid. Every month during the year, on select weekday and weekend evenings, Yerkes Observatory offers observing sessions with our 40-inch diameter refractor telescope, the largest lens telescope in the world, and with our 24-inch diameter reflecting telescope, weather permitting, for participants who are age 10 and up.

Observing sessions with the 24-inch telescope are currently suspended due to scheduled telescope maintenance and upgrading. We anticipate that the telescope will be available again about mid-March for public observing sessions. Please check this page about February 25, 2016 for an update.

Beginning in January 2016, for the first time ever, our 40-inch refractor telescope will be open for limited public observing sessions every month.

We are currently accepting observing reservations for the following dates in February 2016 with the 40-inch refractor:
February 4th, 5th, 6th, 7th, 11th and 12th.

Programs begin at 7:00 pm, last approximately 90 minutes to two hours, and are limited to a total of 12 participants.

Information about public observing dates for the 40-inch refractor and the 24-inch reflector in March 2016 will be posted here about February 25th. Public observing events with the large telescopes at Yerkes are always very popular and sell out quickly. Space on each tour is limited and subject to availability. Scheduled sessions can be canceled due to adverse weather conditions (clouds, rain, snow, high winds or extreme cold) and, in rare circumstances, Observatory event conflicts that arise after public observing dates have been announced.

The cost to observe with the 40-inch refractor is $100 per person, payable the evening of the event by cash, VISA or Mastercard. Reservations are required and can be made by email only at Please use this email address for reservations and questions concerning the 40-inch telescope program only.

For information and questions about the Observatory’s other tours please email (monitored seven days a week) or call us at 262-245-5555, 9:00 am to 4:00 pm, weekdays. The Observatory office is not staffed outside of these hours, or on weekends.

When requesting reservations for the 40-inch telescope program, include the name of the group organizer, an email address they can access the day of the event, their cell phone number and the number of people in the party. Groups of four or more will be asked for a non-refundable 50% deposit three days before the event. Deposits are refunded only if sessions are canceled due to weather conditions, equipment failures or Observatory facility conflicts. Reservation requests will be answered by an Observatory representative with additional information and instructions pertinent to your visit.

Scheduled event dates are removed from the above listings as quickly as possible after each sells out. During winter evenings from the dark sky environment at Yerkes you may see superb views of the moon, some planets, constellations, hundreds of stars, star clusters, nebulae, galaxies, the Milky Way, an occasional meteor and artificial satellites. Binoculars can enhance your viewing experience, but are not necessary.

For information about regularly scheduled Saturday tours, weekday tours, and other events, please click here.