Peter Frinchaboy & Bill Kunkel's mail

Updated on May 10, 2021, 9:36 am

Given that generally our hydraassign files successfully positioned fibers further from the pole, and without any problems at the WIYN fiber instrument in more than three hundred pointings over the last four years our experience suggests that possibly the positioning troubles find their explanation in a residual telescope polar alignment error. Mr. Bremer had remarked that the Blanco Telescope has a significant residual alignment error, as do many if not all equatorially mounted telescopes.

While Wallace's pointing model and correction software does reduce telescope pointing discrepancies, canceling the error on-axis, we wonder if the field rotation correction coefficients that Wallace\'s software produces are passed to the hydra software. Were they not read by hydra, then a three arc-minute telescope misalignment could produce major problem when hydra attempts to observe near the pole.

We would be grateful if this possibility could be looked into, possibly allowing for manual keyboard entry (or its equivalent) of the pointing model generated coefficients. In particular, we should be grateful if this might be resolved on the April 16th engineering night, so that our next observer working on this project April 17th through the 19th could do the fields we had to delete from our current observing program that was, in other respects, highly successful.