Telescope Making I (sage ability)
Telescope Making is an amateur-status sage ability in the studies of Astronomy & Astrology and Delicate Metalwork, enabling the character to fashion a refracting telescope. This includes the grinding and polishing of lenses, the preparation of suitable glass, and the construction of a fitted tube and frame that can be mounted or braced against a fixed support. The best design possible is the "harbour telescope," which is 48 in. long, having a magnification of 25x. Such instruments require precise alignment and careful housing to prevent warping or misfocus, as even slight irregularities in the lens will distort the image.
Contents
Telescopes of this kind are used for identifying ships arriving at port, as they will read the flag atop the sails as the ship crests the horizon, provided the weather is clear and the observer is practised. A well-made instrument may also distinguish hull shape, rigging arrangement and visible armament at a considerable distance.
Lesser telescopes can also be designed and made, using simpler lenses and shorter tubes that are more easily transported. A telescope equal to modern binoculars would have a magnification of 10x to 12x, though with a narrower field of view and requiring steady handling. Such devices are often employed for surveying land, observing fortifications or tracking movement across open terrain.
Construction Time
The time needed to construct a telescope is 1 week, +1 day per 1x of magnification desired. This period assumes the character has access to appropriate materials, including workable glass, abrasives and a stable workspace for grinding and setting the lenses. Interruptions, poor materials or failed lens shaping may extend this time at the referee's discretion. The resulting length of the telescope will be 10 in. per 8x magnification, as greater magnification requires a longer focal length and a more carefully aligned tube.
- For example, a 14x telescope would require three weeks to make and would be 17½ in. long. A harbour telescope would require more than 5 weeks, owing not only to its length but to the increased difficulty in achieving clear focus at higher magnification.
These figures are a matter of gaming convenience; they are not meant to accurately describe the real time needed to make a telescope in the 17th century, as exact figures for different lengths and magnification are not available.
Method
The method begins with selecting and cutting suitable glass blanks, which are then ground to curvature using progressively finer abrasives until the desired focal shape is achieved. Each lens is polished to clarity and tested repeatedly for distortion before being set into a fitted tube, usually of wood or brass, lined to reduce stray light. The lenses must be aligned precisely along the axis of the tube, with simple adjustments made through sliding collars or threaded fittings to achieve focus. Care in assembly is essential, as even slight misalignment will render the instrument ineffective.
Use
The type of telescope that is made is a refracting telescope. "Magnification" indicates the apparent diameter of the object being viewed. Thus, the moon appears to the naked eye to be the size of a coin held at arm's length. A harbour telescope expands this dimension 25 times, becoming as wide as 25 coins placed side-by-side. This enables the viewer to obtain considerable detail of the moon's surface, including shadows and irregularities that cannot otherwise be seen.
A tiny flag at a distance up to 12 miles can be recognised, provided there is sufficient light and the air is clear. Messages can be sent via flag if it is known someone with a telescope is watching, though this requires practice and coordination. Additionally, the size and type of siege weapons can be seen, watching as they are loaded; ships can be seen adjusting their sails; the number of enemy can be virtually counted with some patience. A distant light above the curvature of the earth can be recognized for what it is, rather than mistaken for a star or reflection.
See also,
Astrological Chart
Astronomy & Astrology
Natural Astronomy
