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 reflector telescope, weather permitting, for participants who are age 10 and older.

We are currently accepting observing reservations for the following dates with the 40-inch refractor in May and June:
May 26, 27, 28, 29 and 30
June 2, 3, 4, 8, 9, 10, 12, 14, 15, 16, 22, 23, 24, 25, 26, 29 and 30
The 40-inch refractor programs begin at 9:15 pm in May and 9:30 pm in June.

We are currently accepting observing reservations for the following dates with the 24-inch reflector in May and June:
May 25, 26, 28, 29, 30, 31
June 1, 4, 5, 6, 7, 11, 12, 13, 18, 19, 25, 26, 27 and 28
The 24-inch reflector programs begin at 9:00 pm in May and 9:15 pm in June.

All telescope programs last approximately 90 minutes to two hours.

July dates for both telescopes will be posted about June 25. 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 or high winds) and, in rare circumstances, Observatory event conflicts that arise after public observing dates have been announced or equipment issues.

The program costs are $100 per person for 40-inch refractor program and $37.50 per person for the 24-inch reflector program, 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 telescope programs only.

For information and questions about the Observatorys 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 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 via email 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 spring 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.