On the need for space observations of the umbra/photosphere intensity ratio

We draw attention to the possibility of distinguishing between different sunspot theories by observing: (i) The umbra/photosphere intensity ratio as a function of spot size and (ii) the morphology and time evolution of sunspot inhomogeneities such as umbral dots. In arguing the need for space observations of sunspot intensities we discuss the corrections for stray light for ground based and space observations.The opportunity to use the November 13, 1986 Mercury transit as an in situ calibration event is pointed out.Proceedings of the 14th ESLAB Symposium on Physics of Solar Variations, 16–19 September 1980, Scheveningen, The Netherlands.