CFHT UM2025 - Presentation Details
Abstract Details
Title: Wide Field High Angular Resolution Imaging at CFHT
Presenter: Olivier Lai
Abstract:
In this presentation, we will explore the possibility of implementing wide-field/high angular resolution performance to the CFHT telescope by implementing an adaptive secondary mirror (ASM) for ground layer adaptive optics (GLAO), as well as optical cameras capable of further improving the image quality using an “elastic focal plane”. The renewed interest for such a proposal is motivated by two enabling technologies: - The first is the development of sturdy and reliable adaptive secondary mirrors by TNO; on-sky first light of such a device took place in April 2024 at the IRTF telescope. The imaka GLAO demonstrator at the UH88 telescope is capable of producing FWHMs between 0.25” and 0.35” in good conditions, and unlike traditional adaptive optics, where the performance drops sharply at shorter wavelengths, GLAO still provides improvements down in the visible part of the spectrum and can be used to bolster the blue sensitivity of the telescope, a part of the spectral range which is already a significant asset of CFHT and its site. - The second is the use of Machine Learning (ML) to process video streams of wide field astronomical fields to improve the angular resolution of a reconstructed image by correcting the local tip-tilt due to turbulence in the high layers of the atmosphere. This technique is known as DanceCam, and was first demonstrated on-sky at the C2PU 1 meter telescope at Observatoire de Calern in May 2022. Multiple approaches are possible for implementation, such as keeping the same optical prescription as the current F/8 secondary for the ASM, allowing to use the full suite of current Cassegrain instruments, but with improved (GLAO corrected) seeing; MegaCam could potentially even be used at Cassegrain with improved sampling but reduced on-sky field size, compatible with the unvignetted field through the hole in the primary (~30 arcminute). Alternatively, a smaller ASM could be built with a shorter effective focal length and move the instrumentation focal plane above the primary mirror, allowing for larger unvignetted fields, as vertical measurement profiles of the turbulence indicate that GLAO correction is possible over degree fields on Maunakea.