Baillou, Franciscus, 1738
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photo - whole telescope
Basic Info

Maker: Baillou, Franciscus

Year: 1738

Year Range: -

Year Notes:

Manufacturing Location: Milan, Italy

Signature: “Franciscũs Baillou fecit Mediolani anno 1738”

Signature Notes:


No stand present.

Collection: Adler Planetarium and Astronomy Museum

Accession #: M-431


Project investigation and collection website

Public Notes:

Brown leather covered main barrel with gold tooling. Seven draw tubes are covered with marbled paper with a marbled smear pattern. Brass ferrules, ivory cells for both objective and eyepiece with ivory caps. Signature scratched on the lens.

Length (open): 458 mm by 70 mm diameter

Length (closed): Unconfirmed


Exit pupil:

Object status:

Optical Basics

Objective type: singlet

Optical style

Physical style spyglass

Functional style

Materials: leather, paper, brass, ivory, glass, wood, pasteboard, gold tooling

Optical/Lab Data

Drawtube data:

Drawtube notes:

Objective Data

CA curvature (diopters): CB curvature (diopters): PD lens power (diopters): fD focal length (mm): t thickness (mm): free aperture (mm): full aperture (mm): nD refractive index: ν Abbe No.:
Lens 1 1.17 ± 0.003 -0.01 ± 0.003 0.62 1600.00 0.70 31.50 1.53



Eyepiece 1
fD focal length (mm): free aperture (mm): full aperture (mm): s spacing (mm): CA curvature (diopters): CB curvature (diopters): M magnification: FOV field of view (degrees): Thickness:
Lens 1 61.70 25.90
Lens 2 58.40
Lens 3 51.80
Lens 4 52.60