In order to safeguard the condition of our telescopes, we will observe when it is mostly clear (most stars visible), with humidity levels below 85%, wind speeds below 45 mph, there are no active air quality alerts, and the temperature is above freezing (32 degrees F).

We cannot guarantee clear skies on the night you scheduled, but in the event that the weather does not permit observing with our telescopes (or there are technical issues with the historic equipment), we guarantee a special, exclusive experience where you will explore the night sky from a historical perspective on our indoor evening tour.

If there is lightning or severe thunderstorm risk, we will cancel the event as a safety precaution. You will be fully refunded should we have to cancel because of weather.

Our address is 373 W. Geneva Street in Williams Bay, Wisconsin. Turn into our driveway at Geneva St. and Observatory Place by the Yerkes Observatory sign. Our parking lot is on the southeast side of the building. Stay left in the oval driveway and wind around to the lot. Keep veering left keeping the yellow home on your left. Please do not pull in front of the northside doors of the Observatory.

Our ADA spots are in the main parking lot in the southwestern corner of the lot. They adjoin the pathway to the south (lakeside) doors. We also have EV charging stations in our lot.

The observatory was built in 1897 and so the Great Refractor and the 24” telescopes is not easily accessible. There are several flights of stairs (standard, steep, and tight spirals) that will be climbed and descended during both the clear and cloudy nights. If you have concerns or would like to request accommodations, please contact us at info@yerkesobservatory.org at least 2 business days prior to your tour. Please note that we are an historic observatory, so while we will do our best to provide accommodations, we cannot guarantee them.

Light refreshments will be provided at the beginning of the tour and you are welcome to bring your own water bottle. There are no alcoholic beverages allowed at observing events.

The telescopes are open to the night air and it can get cold, so please dress accordingly.

To enter the Observatory itself, walk the pathway from the lot to the south entrance. We’ll greet you at the doors about 10-15 minutes before your start time. Please arrive 10-15 minutes early to check in. You do not need to bring a printed copy of your ticket with you.

To ensure the quality of the experience for all guests, late arrivals will not be admitted and will not be rescheduled or receive a refund. Space may not be available due to our maximum occupancy per tour. Online reservations are required. Other people with you may not enter the building and browse the exhibits or rooms. Everyone must have a reservation and time slot. Observatory staff members are the only people able to take visitors around the Observatory.

Our Exploring the Night Sky tours are incredibly popular experiences that sell out quickly. If there are no dates available when you attempt to purchase tickets, this is because all of our dates are sold out. If you are interested in being notified when our next round of tickets becomes available, please reach out to info@yerkesobservatory.org.

The Gift Shop will be open at the end of your tour and is a card only service (no cash or check).

Because our construction and restoration is ongoing, Yerkes Observatory may restrict access to or close any of its property and cancel ticket reservations without advance notice, reason, cause, or explanation at any time.