AC90 Captain describes an attempted visual approach with the field not actually in sight and entering IMC at low altitude. Thirty seconds later the field is actually sighted and a visual landing ensues.

Narrative

After descending to an ATC assigned altitude of 3;000 FT MSL; I thought I had the airport in sight so I canceled the IFR flight plan. I then descended to 1;400 FT MSL (approximately 1;000 FT AGL) to remain clear of the clouds and maintain visual with what I thought was the airport. Turns out; the airport was not in sight and I re-entered IFR for about 30 seconds until the airport environment became visible. While in and out of the cloud bases; several glimpses of cell phone towers became visible. The IFR chart only displays one tower east of the field at [about] 620 FT AGL. This close encounter happened between 5-10 miles east of the airport. Once on the ground; a closer examination of the sectional chart revealed two towers east of the field within the 5-10 mile range; one at [about] 300 AGL and one at [about] 440 AGL. The airplane had approximately 400-500 FT vertical separation from these two towers. I made the mistake of calling the field and canceling IFR without the co-pilot having the field in sight. In a crew situation; both crew members should verify the airport is in sight before proceeding with a visual approach or cancellation of IFR. When in doubt; the instrument approach procedure should always be deferred to. My second mistake was descending to 1;000 FT above the field elevation in an attempt to remain clear of clouds. Once again; the instrument approach procedure should have been selected. Once re-entering IFR I initiated a climb to come around for the approach; but soon broke out again with the airfield in sight this time.