Lowitz arcs are nearly always ephemeral and indistinct. They seem special among the halos for being associated with patchy cloud making positive identification difficult. Most images show enhanced views and/or a simulation when the mouse is passed over them or the small key images. You might feel that some of the identifications are overly tentative or conversely that Lowitz arcs are just not there. That is their nature - after 200 years they remain argued over objects!