The FOV really is quite large -- the documents give it at 7900 square degrees. If you take that to be a square patch, it's about 90x90 degrees! And you can't h

The FOV really is quite large -- the documents give it at 7900 square degrees. If you take that to be a square patch, it's about 90x90 degrees! And you can't have it all. I had assumed atmospheric path length would be a problem as the FOV extends toward the horizon, but other optical issues limit you before that. From the arXiv paper I linked nearby: > Angle-of-incidence effects: Commercially-available antireflection coatings have a restricted range of effective angles of incidence, and this places an effective upper limit of 100◦–120◦ on the field of view of an array looking though a single window. The Argus Array’s Key Projects’ requirements easily conform to these limits, especially with the acceptance of slightly increased light losses for telescopes at the edge of the array. In other words, our FOV is about 90 degrees wide, and the coatings are OK to 100-120 degrees.