Basic Data
| Maker: | J. Harris |
| Date (year): | 1850 c. |
| Description: | Harris single-draw wooden telescope |
| Signature: | J. Haris & Son London. Night or Day |
| Collection: | Private Collection |
| Accession #: | B.2 |
| Style: | maritime |
| Objective type: | doublet - crown forward |
| Notes: | Single-draw round wooden barrel achromatic telescope. Signed “J. Harris London Night or Day” in script with flourishes. Lens covers and eyepiece cup missing. Length closed 515 mm, set for infinity c.525 mm. Two-lens eyepiece (one or more additional eyepiece lenses may be missing). |
Objective Data
| Lens 1 |
Lens 2 |
Complete |
| CA curvature (diopters): |
7.90 |
|
|
| CB curvature (diopters): |
|
2.58 |
|
| PD lens power (diopters): |
|
|
2.075 ± 0.003 |
| fD focal length (mm): |
|
|
481.9 ± 0.7 |
| t thickness (mm): |
|
|
6.2 |
| d free aperture (mm): |
|
|
40 |
| nD refractive index: |
|
|
|
| ν Abbe No.: |
|
|
|
Eyepiece Data
| No. of eyepiece elements: | 2 |
(elements of one eyepiece) |
| Lens 1 |
Lens 2 |
Complete |
| fD focal length (mm): |
89.8 |
56.0 |
97.8 |
| d diameter (mm): |
|
|
|
| s spacing (mm): |
|
92 |
|
| CA curvature (diopters): |
|
|
|
| CB curvature (diopters): |
|
|
|
| M magnification: |
|
|
4.9 |
| FOV field of view (degrees): |
|
|
5.3 |
Objective Color Curve Data [(Δf/f)x10-3]
| # |
Wavelength (nm) |
Paraxial |
70% Zone |
Whole Lens |
| 1 |
482 |
|
1.2 ± 0.4 |
|
| 2 |
575 |
|
0 |
|
| 3 |
652 |
|
0.2 ± 0.2 |
|
Attached Files (click to enlarge)
This entry, number 124, was created on 2007-01-21 16:02:13 and last modified on 2007-10-21 16:03:45.
