The Boards of the Histechnica Association and the KIVI Department of the History of Engineering are pleased to invite you to attend a lecture to be delivered by Mr Dr N. de Hilster entitled:

"A quadrant like Blaeu's: Construction, use and accuracy"

Summary of the lecture

The lecture is about the results of the measurements I have recently made with a replica of Snellius' wooden quadrant. The original was made by Blaeu in the early seventeenth century as a successor to the iron quadrant used by Snellius in his measurement of the Earth's circumference.

The construction of the replica (to true scale) was initiated at the request of the television programme Jekels Jacht (broadcast date was on 12 June 2024 via NPO2: https://npo.nl/start/serie/jekels-jacht/seizoen-2/jekels-jacht_4/afspelen) and was made with the assistance of students and teachers from department of furniture construction at Horizon College in Heerhugowaard and the president of Observatory Saturn, Paul Volman. The replica is now in Bergen op Zoom, where it is part of an exhibition on Snellius in the Peperbus.
The replica of Snellius' quadrant is built to Tycho Brahe's design, as he used on Hven. This means that aiming is done with open sights, so there is no telescope on the instrument. All measurements made with this instrument in the recent period were therefore made in this way, and with the lecture I hope to give the listener an insight into the accuracies achievable with such an instrument. Naturally, attention will be paid to the possible sources of error, distinguishing between horizontal (as for a triangulation) and vertical measurements (as for a polar height measurement).

Information on the speaker

nicolàs de Hilster (1965) is a researcher of instruments and measurement methods for navigation, hydrography and geodesy. His PhD thesis, on which he received his PhD at the Vrije Universiteit in Amsterdam in 2018, covers the history, construction, development, use and accuracy of early modern instruments for astronavigation. In addition, Nicolàs is an amateur astronomer, currently doing research on early modern astronomy, and is the Dutch representative of the Scientific Instrument Society (SIS) and web-editor of the SIS and the Scientific Instrument Commission (SIC).

To attend this talk, please register:

- KIVI members can register via the KIVI website

- Members of Histechnica can register through the secretary: hotzeboonstra@gmail.com

- Non-members can register via the KIVI website, cost €5.00.

The lecture will be broadcast live; please click on the link below:

https:// youtube.com/live/UBNl4lzQ9eI?feature=share

There is no charge for this.

board position:

One (or perhaps more) position(s) will soon become vacant on the Board of the KIVI History of Engineering Section. In any case, we are looking for a new treasurer.

For information about this position, please contact the current treasurer:Hans Soutjesdijk, e-mail:stoutjeskunst@xs4all.nl, phone 070 - 3 470 959.

Further contact via: frank.w.vandenberg@gmail.com".

Upcoming activities at Science Center Delft:

Saturday 12 April 2025 at 11:00 by Dr N. de Vreeze: "Icons of Dutch public housing".

Saturday 17 May 2025 at 11:00 am lecture by ir. A. Burgers: "From the Scheldt to the Rhine: The waterway quarrels between the Netherlands and Belgium".

Saturday 28 June 2025 at 11:00am lecture by Dr H.G Heijmans: "The deception of Alexandria; Robert Fryer and the Pocahontas"

A 2-day study tour to Liege and its surroundings will take place on Thursday 22 May and Friday 23 May 2025

On the occasion of Histechnica's 50th anniversary, a book "Out of Failure Making Progress" was published on Saturday 20 April 2024. The book will be available free of charge during the lecture.