Abstract
With the development of astronomy, more and more attention is paid to the survey of dark matter. Dark matter cannot be seen directly but can be detected by weak gravitational lensing measurement. Ellipticity is an important parameter used to define the shape of a galaxy. Galaxy ellipticity changes with weak gravitational lensing and nonideal optics. With our design of an unobscured off-axis telescope, we implement the simulation and calculation of optics ellipticity. With an accurate model of optics PSF, the characteristic of ellipticity is modeled and analyzed. It is shown that with good optical design, the full field ellipticity can be quite small. The spatial ellipticity change can be modeled by cubic interpolation with very high accuracy. We also modeled the ellipticity variance with time and analyzed the tolerance. It is shown that the unobscured off-axis telescope has good ellipticity performance and fulfills the requirement of dark matter survey.
Highlights
The start of the century has seen rapid progress in the study of weak gravitational lensing [1]
It is shown that the unobscured off-axis telescope has good ellipticity performance and is fit for dark matter survey
In this article we make a complete analysis of the PSF property and ellipticity performance of an off-axis telescope
Summary
The start of the century has seen rapid progress in the study of weak gravitational lensing [1]. Gravitational lensing is the deflection of light from distant objects by all matter along its path, including dark matter This is one of the most promising aspects in astronomy. Off-axis telescopes have many advantages over co-axis ones, such as easy stray light control, low-scattering property, filled pupil for wave-front sensing, room for adaptive optics, larger throughput, and so on [6]. It has got simpler and sharper diffraction pattern, which means higher resolution and some advantages in ellipticity performance. It is shown that the unobscured off-axis telescope has good ellipticity performance and is fit for dark matter survey
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