File:ASDI spectral plus angular diversity scaled.svg

English: Schematic observations obtained by angular-spectral differential imaging, scaled to align the coronagraphic point-spread function and speckle pattern. Each frame (gray border) in the 3-by-3 grid is an image of the observed solar system at wavelength $\lambda$ and parallactic angle $\theta$. The coordinate system in each frame represents the (projected) separation from the host star in the center, e.g., right ascension and declination. The point-spread function and speckle pattern are shown in red, an off-axis source (like an exoplanet) is shown in blue, and its trajectory through the observation cube is shown as a dashed blue arc. The center of each frame, coinciding with the position of the host star, is indicated by a black circle. While only $9$ frames are shown here, full observations typically consist of thousands of frames. The frames are scaled radially from the center outwards by the ratio of a reference wavelength $\lambda_0$ (typically the largest wavelength in an observation) over the wavelength of a frame, also called the scale factor $\lambda_0 / \lambda = s$. The coronagraphic point-spread function and speckle pattern are aligned throughout the entire cube. This also misaligns off-axis sources, both radially and azimuthally. Ideally, the PSF and speckle pattern are now the same in every frame and can be modeled. $\lambda_0$ is typically the largest wavelength in an observation.