This page traces one photon's journey and, with it, the whole pipeline. 1) Capture: photons cross light-years, enter the telescope, and are recorded as a noisy raw frame. 2) Calibration: bias/dark/flat frames remove the camera's electronic baseline, thermal signal, and optical defects. 3) Stacking: dozens to hundreds of calibrated frames are aligned and averaged, raising SNR by √N and rejecting outliers (satellites, cosmic rays). 4) Stretching: the faint linear data is non-linearly stretched so dim detail becomes visible without blowing out stars. The result: a clean, detailed image from individually unusable frames.