威尔逊效应是以麦可法莱恩天文台工作的苏格兰天文学家威尔逊之名命名的。他在1769年注意到太阳黑子的形状，明显的受到太阳自转的影响，在边缘显得较为平坦。此一观测证明太阳黑子是太阳表面上的现象，此外，现在所谓的威尔逊效应是：本影和半影在形状上的改变，其实是本影在光球层上稍微凹陷在视觉上造成的透视效果。凹陷的程度很难正确的测量，估计大约是1,000公里。

尽管表面的凹陷可以用威尔逊效应广泛的解释，Bray和Loughhead (1965)指称威尔逊效应的真正解释在于黑子物质相对于光球层的透明度。他们在其著作的书中第93至99页说明他们的想法。C.H. Tong在2005年也提出了类似的解释。

In 1769, during solar cycle 2, a Scottish astronomer named Alexander Wilson, working at the Macfarlane Observatory, noticed that the shape of sunspots noticeably flattened as they approached the Sun's limb due to the solar rotation. These observations showed that sunspots were features on the solar surface, as opposed to minor planets or objects above it. Moreover, he observed what is now termed the Wilson effect: the penumbra and umbra vary in the manner expected by perspective effects if the umbrae of the spots are in fact slight depressions in the surface of the photosphere. The magnitude of the depression is difficult to determine but may be as large as 1,000 km.