Some nomograms for sundials use a logarithmic portrayal because the nomogram is often an additive device, and multiplication is done by adding logarithms. However, some nomograms use division directly (N or Z) and some use multiplication directly (circular), so, there is variety. Here are several types:-
type 1 | | | additive nomogram C = L + R must use logs for * and / type 2 | \ | dividing nomogram C = L / R no logs for division type 3 ( | ) multiplying nomogram C = L * R no logs for multiplying type 4 \ /_ adds reciprocals 1/C = 1/L + 1/R
For those who wish to design nomograms and understand them in more detail, and sundial plates using nomograms, here are some highly detailed notes (if you buy the big book) on doing it, they will save you a lot of time. The process for the horizontal dial is shown, the vertical dial being the same but co-latitude, which is also shown. Further, the DeltaCAD macro: nomogram.bas builds vertical and horizontal dials, but since DeltaCAD (as I have it) only does natural logs as opposed to base 10, these macros use Napierian logs.
DeltaCAD macro is a complete v and h dial, a sunrise/set, a polar/meridian dial with calendar data nomogram (both the three vertical line as well as the N or Z nomogram), and a vertical decliners SD, SH, and DL with the v-dec hour lines worked using SH and DL. The DL macro choice has two variations, the second showing the use of differing line separations (xL, xC, xR) and the modulus (scale) of the right line (mR) which you may change. Also has the analemmatic dial nomogram. Does nomograms type 1,2, and 3.
Lazarus/Pascal code for the h, v, m/p, v-dec dials, and sunrise/set times all in one ZIP file. Does nomograms type 1, 2, and 3. In essence, everything the DeltaCAD macro does except exporting the images, which needs a screen screen capture program such as this (I have NOT used it, I use PhotoMax Pro).
Printed nomograms from both DeltaCAD and Lazarus/Pascal are in PDF form. The nomograms are also in the free appendices. This book of printed nomograms may be lower quality print than if you run the DeltaCAD or the Lazarus based program, which you are encouraged to do. the appendices however have very high quality nomograms.
NOTE: Chapter 32 in Illustrating Time's Shadow covers more detail, however, the most detail is in Supplemental Shadows and takes some 30 pages, and supplements chapter 32, and go into more detail on line separation, modulus (line scaling), and details on where "0" is on the three common nomogram types. The free appendices to Illustrating Time's Shadow have the nomograms in appropriate sections, and the formula appendix also has a short summary of the three nomogram types, their formulae supported, and where '0' is, and other issues with 0.