The Southworth Planetarium is located in the lower level of the B wing in the Science Building on the University of Southern Maine's Portland campus. Access is typically off of Falmouth Street, but you can also enter the building from the University side of the building.
Once you enter the main doors, next to the drop off area, you are facing the upper level of the dome. You need to go to your right around this area until you come to the stairs leading down to the planetarium entrance, gallery, and store.
There is elevator access if you need it, you will find it opposite the stairs on the back side of that wall.
Parking is on the street. The south side of Falmouth Street is City of Portland parking and you will have to use the Portland app to pay for your parking. On the north side of Falmouth Street there is free 2-hour parking. You can also park in the University parking structure on Bedford Street for $4/hour. You'll need a smart phone to go online and pay.