STUDIES ON HIGH-RESOLUTION IMAGING WITH TWO-COLOR SPECKLEGRAMS

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A short exposure image of a stellar object observed from the ground exhibits a speckle-like pattern because of atmospheric turbulence of the earth. However, such a specklegram contains the information of the object with diffraction-limited resolution of a telescope. The speckle interferometry is a simple method to get high-resolution image apart from adaptive optics. When there is a high correlation between two specklegrams with greatly differnt wavelengths, high-resolution imaging is feasible at one wavelength by reference to a specklegram at the other wavelength where the stellar object appears as a point-source or a reference star is available.The purpose of this research project is to establish high-resolution imaging method with two-color specklegrams by analysing specklegrams at two greatly different wavelengths. We conducted observations of Capella and Vega with our two-color speckle camera attached to the 90cm or 188cm telescope at the Okayama Astrophysical Observatory, NAOJ.The detection wavelengths are 400nm or 450nm at the short wavelength and 800nm at the long one. These wavelengths correspond to the extremes of the visible region and the ratio is about two.The shift-and-add operation for specklegrams at one wavelength results in an accompaningly reconstructed image at the other wavelength. It is clarified that the reconstructed image at one wavelength by reference to specklegrams at the other wavelength is better than the pseudo long exposure image, which is produced by centering and adding the gravity of specklegrams. This shows that high-resolution imaging is possible by utilizing specklegrams at the different wavelength. The application of our method to visible-NIR observations remains as a future project.