We have constructed a high-speed image stabilization system, BESSEL, which mounts to the 8-in. refractive telescope coupled to the ray white telescope at steward observatory. The high-speed tip/tilt mirror platform is controlled by an Andor electron multiplication EMCCD enabling wavefront correction at a rate exceeding 1 kHz. BESSEL achieves on-sky Strehl ratios of 98–99% at lambda) = 800 nm when the telescope aperture is stopped down to half the Fried parameter (typically D = 25.4 mm, where D is the diameter of the effective telescope aperture). Utilizing high Strehls and the technique of roll subtraction enabled BESSEL to resolve the binary, ADS 10418AB (more commonly known as a Her), with separation of only 0.719(lambda)/D and a delta magnitude of ~3 mag at 800 nm. In addition, Arcturus was observed with BESSEL to explore a relatively untested region of Strehl versus D/r0 parameter space in the optical, specifically at small (~0.5D/r0). We find that in this regime space quality, very high Strehl (~99%), optical imaging can be obtained from the ground when D/r0 < 0.5 as one approaches the inner scale of turbulence. Because of BESSEL’s demonstrated high Strehls, it is an ideal platform for inexpensive, initial, on-sky characterization of space-based coronagraphs, for which it will be used in the near future.

Publication Date



Note: imported from RIT’s Digital Media Library running on DSpace to RIT Scholar Works in February 2014.

Document Type


Department, Program, or Center

Chester F. Carlson Center for Imaging Science (COS)


RIT – Main Campus