Using Paul's link, it references River Road off of Rt.9 at Ulster Park. Following River Road East(north) you will also come to a very small park right off the road along the water's edge called "Lighthouse Park". If you pull off at the park, you are exactly parallel with the light, and a nice unobstructed view too.

If you check out the HL Gallery Pages, it includes a shot I took from that exact point in the morning with a 205mm zoom.

http://www.harbourlights.com/galleries/rod_watson.htm