This chart is a top-down altitude-azimuth plot: the center is straight up (zenith, altitude 90°) and the outer ring is the horizon (altitude 0°), with compass direction running around it. A telescope's limiting magnitude grows with aperture because a bigger mirror collects more photons: mlim ≈ 2 + 5·log₁₀(Dmm). Its angular resolution is set by diffraction (Dawes' limit ≈ 116″/Dmm) combined in quadrature with atmospheric seeing, since the two blurring effects are independent and add like uncorrelated errors.
m_lim = 2 + 5·log10(D_mm)
Dawes = 116 / D_mm (arcsec)
res = sqrt(seeing² + Dawes²)
FOV = sensor_width / focal_length (radians)
SNR = signal / sqrt(signal + sky·N_pix + read²·N_pix)
Field of view narrows as focal length (aperture × focal ratio) grows. Signal-to-noise grows with aperture² and with the square root of exposure time, since collected light scales with mirror area and total time while shot noise only grows with its square root. A narrowband Hα filter throws away most starlight but blocks almost all sky glow, so it dramatically improves contrast on the nebula even though it dims ordinary stars — the real reason astrophotographers reach for it under light-polluted skies.