Related arguments apply to a possible subsun, which is also an ice halo phenomenon. A subsun is commonly seen in isolation, but is part of a complex display called a subparhelia, mirroring below the horizon the appearance of the normal parhelia above. The subsun is a virtual image of the sun and occupies the equivalent position in the inverted display, which is produced in this case by a layer of platelet ice crystals below the altitude of the observer. For this reason subsuns are commonly seen from aircraft.

A subsun appears as a single patch of light, varying from a near-specular solar image to a fuzzy ellipse (in rare cases surrounded by concentric ellipses called Bottlinger's Rings), with a vertically oriented major axis that further devolves into a vertical streak called a sun pillar. The single subsun appears directly below the sun, which in the present case would be at azimuths between ~224° and 227°, and therefore does not explain two horizontal ellipses disposed side by side, the westernmost of which is seen always to the E of the Casquets Light n1The reflection geometry of the ice halo is bilaterally symmetrical about a vertical axis passing through the azimuth of the sun, whereas in this case both UAPs were seen (for some minutes) offset asymmetrically by several degrees to the left (E) of the ~220°azimuth of the Casquets lighthouse (a definite and familiar visual reference), whilst the sun was at an azimuth ~225° to right of Casquets and moving W (see Fig.23)..

Rarely a very well developed subparhelia can produce a bright subsun attended either side by its own pair of sub-sundogs. But these will be at least 44° apart and therefore nowhere near close enough. The subsun itself would be much more prominent than the pair of sundogs. And most importantly, the depression angle below the horizon of this entire display will be equal to the elevation angle of the real sun above the horizon, i.e. about -43°, whereas the UAPs were seen within a degree or two of the horizon.

In the present case both the geometry and the meteorology are inconsistent with a subsun. Most obviously all witnesses were thousands of feet below the freezing level, which was at about 10,000ft (Fig.22; see also Fig.20, Section 5). There is no evidence that lines of sight could have intersected the top surface of a layer of ice crystals.

Plausibility (0-5): 0