Transients in the Palomar Observatory Sky Survey

[Eburacum]

There are more stars near the ecliptic plane, therefore more emulsion flaws would be removed from the full data set, making the distribution non-random.

I agree, and that is the point I was trying to make (although probably in a hamfisted and unclear way). The distribution of emulsion flaws was presumably random before the ones closest to the ecliptic were removed.

I note that Villaroel says that only northern hemisphere plates were considered; if so that removes the big bulge in Sagittarius, which is in the southern celestial hemisphere. I may have to think again.