Hi Jamie, Thinking along the lines of your 15 Dec post on alternative AZ jackknife, but motivated more by the apparent symmetries of the tile-average beam mistmatch illustrated in Abby's 17 Dec post (and Randol's 28 Nov post), I'll propose another alternative jackknife: T1 & T2 dk [68,113] + T3 & T4 dk [248,293] vs T1 & T2 dk [248,293] + T3 & T4 dk [68,113] This jackknife will have overlap only in the central portion of our map, but it may reveal inconsistency there due to residual tile-average beam mismatch which flips 180 from T1&T2 to T3&T4 (with the physical tile orientation...and the near field mismatch). Is this jackknife easy to construct? J -- ___________________________________________________________________ John Kovac jmkovac(a)cfa.harvard.edu Assistant Professor, Astronomy and Physics, Harvard University 160 Concord Ave rm 310, Cambridge MA 02138, 617-496-0611