A Case Study on Low-Cost Tip-Tilt Adaptive Optics Systems for the Apache Point Observatory 3.5-m Telescope

A new echelle spectrograph is proposed for the 3.5-m telescope at Apache Point Observatory (APO), part of an effort to replace aging instrumentation and ensure its longevity. To further improve the capabilities of the instrument, we investigate the benefits of commissioning a low-cost adaptive optics system correcting low-order aberrations, namely tip-tilt. We compare two methods of correcting tip-tilt: centroid tracking and peak tracking. Centroid tracking follows the image's first order moment, and peak tracking, also known as shift-and-add (SAA), follows the brightest peak in an image. Tracking algorithms are developed and applied to high speed images from APO to determine their levels of improvement in terms of enslitted energy as a function of slit width. We found centroid tracking consistently performs better, at a maximum increase of at least 2\%. The located centroids were also converted into a measurement of vibrational power, indicating overall wind speeds of 5--7 m/s above APO.