File:H1 low 250.jpg
H1_low_250.jpg (250 × 294 pixels, file size: 81 KB, MIME type: image/jpeg)
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Summary
[edit]DescriptionH1 low 250.jpg |
English: John Harrison's H1 marine chronometer. It took Harrison about five years to develop this chronometer. Its sea trial was in 1735 on HMS Centurion to Lisbon and HMS Orford returning to England. It weighs 34 kilograms (75 lb) and was originally housed in a glazed wooden case about 120 centimetres (3.9 ft) in each dimension.
Instead of a pendulum, it employs a pair of rocking bars with balls on the end and constrained with helical springs. The equal and opposite movement of these bars was less susceptible to being affected by a ships movement than a pendulum would be. Harrison's grasshopper escapement connects the bars with the rest of the mechanism. Some of the cog wheels are of wood which has self-lubricating properties. Gridirons provide temperature compensation by modifying the effective length of the helical springs. For this invention Harrison received £250 (compared with the £20,000 offered for a full solution) from the Board of Longitude. Harrison called it a "timekeeper". The bar-balances like elongated dumbells do not run in conventional bearings. Instead they roll on pairs of plates set at 45° to the vertical and at 90° to each other. These plates, which only move through very short distances are on the ends of long arms pivoted near the bottom of the instrument. The counterweights to these arms are the brass knobs looking like control knobs at the very bottom. This and other devices mean that the clock requires no lubrication.
Better images: pixgood and my-time-machines. Shot without flash, 800 ASA setting. |
Date | |
Source | Own work |
Author | Phantom Photographer |
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current | 18:55, 24 February 2011 | ![]() | 250 × 294 (81 KB) | Phantom Photographer (talk | contribs) | {{Information |Description ={{en|1=Photograph of John Harrison's H1 clock. Low resolution for illustrative purposes only, and to discourage potential commercial use.}} |Source ={{own}} |Author =[[User:Phantom Photographer|Phantom Ph |
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Metadata
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Camera manufacturer | Canon |
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Camera model | Canon PowerShot A470 |
Exposure time | 1/10 sec (0.1) |
F-number | f/3 |
ISO speed rating | 800 |
Date and time of data generation | 13:46, 24 February 2011 |
Lens focal length | 6.3 mm |
Horizontal resolution | 180 dpi |
Vertical resolution | 180 dpi |
File change date and time | 18:36, 24 February 2011 |
Y and C positioning | Centered |
Exif version | 2.2 |
Date and time of digitizing | 13:46, 24 February 2011 |
Image compression mode | 5 |
APEX shutter speed | 3.3125 |
APEX aperture | 3.15625 |
APEX exposure bias | 0 |
Maximum land aperture | 3.15625 APEX (f/2.99) |
Metering mode | Pattern |
Flash | Flash did not fire, compulsory flash suppression |
Color space | sRGB |
Focal plane X resolution | 13,714.285714286 |
Focal plane Y resolution | 13,714.285714286 |
Focal plane resolution unit | inches |
Sensing method | One-chip color area sensor |
Custom image processing | Normal process |
Exposure mode | Auto exposure |
White balance | Auto white balance |
Digital zoom ratio | 1 |
Scene capture type | Standard |