  Magnetic guiding fields in combination with energy dispersive semiconductor
detectors have been employed already more than 50 years ago for in-beam
internal conversion electron spectroscopy. Even then it was recognized that
efficiency modulations may appear as function of the electron energy, arising
when electrons hit a baffle or miss the sensitive area of the detector. Current
high precision beta decay experiments of polarized neutrons with conceptional
similar experimental devices resulted in a detailed study of the point spread
function (PSF). The latter describes the radial probability distribution of
mono-energetic electrons at the detector plane. Singularities occur as function
of the radial detector coordinate which have been investigated and discussed by
Sjue at al. (Rev. Scient. Instr. 86, 023102 (2015)), and Dubbers
(arXiv:1501.05131v1 [physics.ins-det]). In this comment a rather precise
numerical representation of the PSF is presented and compared with
approximations in the mentioned papers.
