A General Aviation pilot reported entering Class D airspace after assuming it had a ceiling similar to where this pilot usually flies.

Narrative

I was with another private rated pilot and we had taken off from HPN approx. 40 minutes before and flew the Hudson river exclusion. I was the Pilot Flying the Hudson river's northbound leg heading back to ZZZ. As we passed the alpine tower @ 1;000 ft and reached the 3;000 ft floor of the Class B shelf; I started a climb to 2;800 ft heading 045. The Pilot Not Flying; suggested we fly east as there might be more sights along the shore to see. I then turned east and asked if HPN's Class D ceiling was 2;600 ft without checking it myself since he had his iPad open; even though I also had an iPad with the chart open. He stated it was 2;600 ft and I continued flying an easterly heading; bringing us approx. 4 miles south of HPN; mistakenly through their airspace. I noticed jet traffic departing 16 @ HPN in front of us; when the Pilot Not Flying suggested we turn south to avoid HPN's airspace. That's when I questioned him again on the ceiling of the Delta airspace and he said it was 3;000 ft. I immediately contacted HPN's Tower and told them of our mistake. The controller confirmed our mistake and that his airspace went up to 3;000 ft. I apologized for my mistake and we continued on our way.I believe the problem arose because instead of asking what the height of their airspace was; I asked if it was 2;600 ft; typical Delta airspace where we usually fly. I believe expectation bias played a role. Contributing factors were that this was my first time flying from the right side and not being 100% comfortable; I was more focused on flying than I was on navigating and should have relayed that to the other pilot.