An exceptionally bad run of luck has resulted in an unusually long period without good flats. Towards the end of this period it appears that a significant change in the flats occurred (between 980401n & 980403n) which has resulted in the rejection of J & H flats due to too many being different between the new flats and the canonical flats. The difference maps across this break (when available) have been included below for comparison purposes.

We think the best approach at this stage would be to set a "hardware" break after 980401n so that subsequent nights will be processed with more representative flats. At present this would require reprocessing of only 2 nights.

Flats Summary

980320n

Taken & used and look great

980321n

Taken & used, but look a little ratty due to a partial warm-up. But within spec.

980322n

Taken, but not on tape due to write errors.

980324n

Taken, but hit by timeout. j_m & h_m flats produced, but processing aborted at K due to insufficient frames for fitting

980325n

Taken & used despite lots of clouds, and looking a little ratty at K (but still within spec).

980328n

Not taken due to clouds.

980331n

CPU froze during flats, insufficient frames for K, but j_m & h_m flats produced.

980401n

Flats truncated due to a dec limit error. Insufficient frames for J, but h_m & k_m flats produced.

980403n

Flats taken, but only K canonized. J & H rejected because of too many new-old pixels are different

980404n

Flats taken, but only K canonized. J & H rejected because of too many new-old pixels are different

(Note that the "_m" flats indicate that morning flats were takend and created for these nights in some bands, but the missing band prevented processing from proceeding further)

Difference Maps for J, H, & K

In all of these images the display range is set at -0.02 to 0.02.

980331n

980401n

980403n

980404n

Difference between 980401n and 980403n at H