SHIMM: A Low-Cost Portable Seeing Monitor for Astronomical Observing Sites

Abstract

Characterisation of atmospheric seeing and optical turbulence is crucial for the design and operation of modern ground-based optical telescopes. With a new generation of extremely large telescopes being proposed and constructed, new obstacles will be faced with regards to imaging through our turbulent atmosphere. The Differential Image Motion Monitor (DIMM) has been a commonly employed seeing monitor at astronomical observing sites across the world. For decades it has inexpensively provided sites with measurements of the Fried parameter (r0). In this thesis a variation on the current DIMM design will be presented. The Shack-Hartmann Image Motion Monitor (SHIMM) employs a low order Shack-Hartman (SH) lenslet array instead of the two hole aperture mask utilised by the DIMM. The SHIMM is a low-cost, portable instrument, comprised of off-the-shelf components, making it easily duplicated and therefore ideal for comparisons of atmospheric conditions at large observing sites.

In this thesis the four key advantages of the SHIMM will be addressed. By
utilising a SH lenslet array the SHIMM can employ methods for estimating the value of r0, independent of noise; estimate the atmospheric coherence time; correct for the effect of scintillation on the measurement of r0; and produce a low-resolution fixed three layer turbulence profile. On-sky results of each feature will be presented in this thesis.