| RefNo | MOB/111 |
| Level | Item |
| Title | Speculum mirror for a reflecting telescope |
| Creator | Newton; Sir; Isaac (1642-1727); natural philosopher; mathematician |
| Date | c.1671 |
| Description | Small, slightly concave round metal mirror polished on the front face, some tarnishing. A trace of a sprue is visible on the rear face indicative of casting in a closed mould. There is some residue of red wax on the rear.
Historically associated with the early reflecting telescope constructed by Sir Isaac Newton in 1671 and held by The Royal Society (MOB/005). However, the speculum has a diameter of 59mm which is too large for the 1671 Newton telescope cell (54mm in diameter). According to analysis carried out in 1979 the focal length of the speculum mirror is about 190.5mm, this does not match the 1671 Newton telescope or the values Newton gives for its focal length, reinforcing the conclusion that this speculum was not part of that instrument. |
| Extent | 1 item |
| ObjectName | Scientific Instrument |
| Materials | Metal |
| Dimensions | 59 x 59 x 9mm |
| AccessStatus | Open |
| RelatedRecord | MOB/005 |
Fellows associated with this archive
| Code | PersonName | Dates |
| NA8414 | Newton; Sir; Isaac (1642 - 1727); natural philosopher and mathematician | 1642 - 1727 |