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🔭 Keplerian TelescopeRay Optics · Interactive
Objective f₀ 120 mm
Eyepiece f_e 30 mm
Object angle 4.0 °
Adjustment
Mag –
Eye∠ –
Magnification –
Tube Length –
Obj. angle –
Eye angle –
Obj. f₀ 120 mm
Eye. f_e 30 mm
Angle 4.0 °
Mode
ℹ

Construction Rays

Ray 1 — Parallel: enters ∥ to axis → refracted through F′ₒ → enters eyepiece → exits ∥ (normal adj.)
Ray 2 — Central: passes through optical centre of L₁ undeviated → diverges from I → passes through centre of L₂ undeviated
Ray 3 — Focal: aimed at front focal F_e of eyepiece → after L₂ emerges ∥ to axis (normal adj.)
Lens eq (sign conv.)1/v − 1/u = 1/f
Obj. image (u→−∞)v = f₀
Normal magnif.M = −f₀/f_e
D (near point)250 mm
Normal adj.:M = f₀/f_e (angular, inverted) │ Near-point:M = (f₀/f_e)(1 + f_e/D) │ Tube (normal):L = f₀ + f_e │ Near-point obj. dist.:u_e = f_e·D/(f_e + D)
M = f₀/fₑ= 4.0×