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 and the third largest telescope available for public viewing in the world, and with our 24-inch diameter reflector telescope, weather permitting, for participants who are age 10 and older.

Both telescopes were formerly used for astronomical research and are now available for public observing opportunities. For most participants either will likely be the largest telescope they will have access to for viewing the night sky in detail. The difference between the views presented by the refractor vs. the reflector is dramatic, though. For an affordable, general night sky tour and introduction to astronomy we suggest reservations with the 24-inch reflector. For a truly once-in-a-lifetime and unforgettable observing experience using the same telescope as some very famous astronomers over the past century, we suggest the 40-inch refractor.

We are currently accepting observing reservations through Labor Day weekend 2018 with the 40-inch refractor. Note that reservations are required for the observing programs. We do not accept walk-ins on the nights of these events.

The descriptions of the different “multi-object” and “single object” programs are listed below. See instructions, also below, for making reservations. RESERVATIONS AND QUESTIONS ARE ACCEPTED BY EMAIL ONLY, NO PHONE CALLS PLEASE. Failure to follow reservation instructions for any large telescope program will result in a delayed response.

Traditional 40-inch refractor “multi-object” tour sessions, $100 per person, length 2-1/2 hours, all sessions begin at 9:00 pm. Sessions are limited to 16 total participants. RESERVATIONS ACCEPTED FOR GROUPS OF 1 TO 4 PEOPLE ONLY. No reservations will be accepted in August for groups larger than 4 people. Multi-object tours feature viewing through the eyepiece of a combination of four to six different well-placed objects in the solar system and in the Milky Way galaxy.

We are currently accepting reservations for these dates for the 40-inch refractor telescope and our multi-object program:

All multi object dates scheduled in August are sold out.

New 40-inch refractor “single object” tour sessions, $45 per person (includes one Starlight Festival T-shirt per person), length approximately one hour, CHOOSE FROM A START TIME OF EITHER 9:00 pm or 10:30 pm (based on availability shown below), sessions limited to 24 total participants, RESERVATIONS ACCEPTED FOR GROUPS OF 1 TO 6 PEOPLE ONLY. No reservations will be accepted in August for groups larger than 6 people. Single-object tours feature viewing through the eyepiece of one well-placed object in our solar system and in the Milky Way galaxy.

We are currently accepting reservations for these dates and times for the 40-inch refractor telescope and our single-object program through Labor Day weekend:

August 18, 24, 25, 26 and September 1 and 2. -- ONLY the 10:30 pm sessions for these dates have availability. All 9:00 pm sessions are sold out.

August 26 and 31 -- 9:00 pm and 10:30 pm programs have availability.

For the “single object” tour session dates listed above (based on the date and availability), please specify either the 9:00 pm or 10:30 pm start time.

We are currently accepting observing reservations for the following dates in August 2018 with the 24-inch reflector:

August 15 and 19.

24-inch reflector programs last about 90 minutes to 2 hours and start at 8:30pm.

Labor Day weekend public observing dates with the 24-inch reflector will be posted here by August 20.

The public observing programs with the 24-inch reflector and 40-inch refractor telescopes at Yerkes will be temporarily suspended after Sunday, September 2, 2018. No public observing sessions will be available after that date until further notice.

Public observing events with the large telescopes at Yerkes are very popular and often 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, storms or high winds) and, in rare circumstances, Observatory event conflicts that arise after public observing dates have been announced or due to equipment problems.

The program costs are $100 per person for the 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 use this email address for reservations and questions concerning the telescope programs only.

IMPORTANT: Reservation requests MUST include the following information:

  • The name of the group organizer.
  • An email address the group organizer can access the day of the event.
  • The group organizer’s cell phone number.
  • The number of people in the party.
  • The telescope program in which the group wished to participate (""reflector" or "refractor").

Reservation requests will be answered by an Observatory representative via email with additional information and instructions pertinent to your visit. Confirmations are sent periodically throughout the week so please be patient - we are a small staff with many duties at Yerkes. Please do not send multiple emails as it slows our response times.

For information and questions about other Yerkes tours please email (monitored seven days a week) or call us at 262-245-5555, ext. 825, 9:00 am to 4:00 pm, weekdays. The Observatory office is not staffed outside of these hours or on weekends.

Scheduled event dates are removed from the above listings as quickly as possible after each sells out. During late spring and early summer evenings from the dark sky environment at Yerkes you may see superb views of the moon, constellations, hundreds of stars, star clusters, nebulae, galaxies, the Milky Way, an occasional meteor and artificial satellites.

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