BACKGROUND
The two nomograms are presented here, GUN & GIN. The names, (GUN = Gnomonic Universal Nomogram and GIN = Gnomonic Instrument Nomographic) are poor!
A nomogram = a diagram representing the relations between three or more variable quantities by means of a number of scales, so arranged that the value of one variable can be found by a simple geometrical construction
They were developed as a fun exercise in laser engraving/cutting using cheap MDF and acrylic. They have little or no practical use - but, nevertheless, will provide the Longitude corrected Equation of Time & time of Solar Noon correct to a within a few seconds .
The author was looking to improve on the EoT device used in Pilkington's Sol Horometer where the Equation correction was incorporated by an ingenious nomographic rotation and lineation.
Pilkinson's Sol Horometer ca 1914
Outer Ring is rotated to line up 2 dates (e.g. 5th June), which provides the correct rotation to correct for the Equation of Time
Showing 10th December selected on Brian Huggett's Mark II Heliochronometer
Click on images to enlarge & view captions
GUN : GNOMONIC UNIVERSAL NOMOGRAM
A large impractical device. It works for any day in the 4-year leap cycle and for any Time Zone. It provides the Equation of Time, Longitude Corrected Equation and Time of Solar Noon.
The GUN is made of three layers of 4mm high quality MDF. Each layer is separated by 0.5mm PTFE, providing lubrication to the rotating central section. The centre section is rotated by a little cog (not visible in this image) located on the brass axle seen top right corner.
Outer Stationary Ring
Plus Inner Rotating Annulus
Plus Stationary Central Equation Grid
Plus Acrylic Alidade
Rear View with Instructions
Example of GUN in operation
1st October 2019 : Zone 1
Read EoT
Read EoT + Longitude Correction for Paris
GIN : GNOMONIC INSTRUMENT NOMOGRAPHIC
Another poor name, but a practical Device - set up to cover any longitude range. The one below was made for the Great Britain and Eire.
This slide rule was built of (a) base of 4mm MDF, (b) a layer of 1mm PTFE and (c) the top & slide of 4mm MDF. The alidade was 3mm Acrylic.
There are two designs available for this device to be (a) cut on a laser (b) printed on card
The operation of both versions is shown below, (a) covering the longitudes of France Métropolitaine (b) covering the longitude of EST in the USA
Step 1 : Parked
Step 2 : Date Marked
Step 3 : Dates Aligned
Step 4 : EoT Read
Step 5 : Longitude Marked
Step 6 : Total Correction (Solar >> Standard Time) Read
Base with Instructions
Card Version covering USA EST
Click on images to enlarge & view captions
The algorithms used provide the EoT are within +/- 1 second precision. If the device were perfectly made, the results can be read to within almost that precision, using the provided Verniers
If anyone wants the graphics to make GIN or GUN, the author would be happy to provide them with the art-work (for their specific time zone, in the case of GIN). I have versions for the UK, France (translated into French) and US-EST immediately available. Use the Contact button on the left.
