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No Northern NRES; Improving focus on 1-meter telescopes

Jul 31, 2020

The NRES unit at Wise Observatory was taken offline yesterday because the acquisition/guide camera failed. The Wise staff is examining the spare camera that is at the site, and another spare camera was sent from LCO HQ today. We will get the camera replaced as soon as possible. ---- The NRES unit at McDonald Observatory has been offline for several months because of a vacuum leak. Now that the site is accepting visitors again, we plan to send an engineering team there in mid-August. The team will tackle a variety of maintenance tasks, including the NRES vacuum leak, to bring our equipment back to full strength. With both the Wise and McDonald NRES units out-of-commission, requests to observe northern targets with NRES will be rejected by the scheduler.

Several weeks ago, we launched some specialized software that iteratively improves a telescope's focus. The code has been deployed to the three 1-meter telescopes at SAAO and the 1-meter telescope in Dome B at Siding Spring. The code was developed and tested beginning back in January. The focus correction algorithm exploits the astigmatism in the telescopes' guide cameras. If a telescope is out-of-focus, stars in guider images appear elongated, and the orientation of the elongation indicates the direction of the defocus. The orientation is used to nudge the secondary mirror position in small increments until the stars appear round again. The corrections are only applied between exposures with the science camera. Consequently, the algorithm is more beneficial for science programs that request a series of short exposures. We have been monitoring the algorithm's performance, and although it's not perfect, the benefits clearly outweigh the errors. We will continue to test and deploy the algorithm to other 1-meter telescopes.