Looking for the Wndsn store? This way, please.

538 pages, black & white. 197 graphics, 31 tables. Perfect bound. 8" x 5" (20.5 x 13.5 cm). Also available as hardcover.

## Errata for the 5th Edition

### Page 29 in the hardcover and page 31 in the paperback edition

Sequence of steps:

1. To install, knot the string to the device through the provided hole.
2. Add marking knots at 57.3/2 and 57.3/3.
3. Measure a length of 57.3 cm (22.56 inches) from eye to device and add another marker knot.
4. Make a small loop at the end to fasten the plumb line weight.

### Page 252 in the hardcover and page 270 in the paperback edition

For The Procedure on the Unequal Hour Quadrant, an additional step is required at the end of the given procedure:

• For days other than the equinox, the declination (δ) has to be added: `H = (90° − φ) + δ`.

Plus a reference to page 243 (hardcover) or page 259 (paperback); Calculating Sun Altitude.

## Errata for the 4th Edition

### Page 68

10 MIL = x100 = 5.729 0.5729°
100 MIL = x10 = 57.29 5.729°

### Page 270, Fig. 112

Figure 112 is supposed to represent Equation 19:

``````sin(ortive amplitude) = sin(declination) · sec(latitude)
``````

which can be calculated graphically as:

``````sin(ortive amplitude) = sin(declination) / sin(co-latitude)
``````

Figure 112 displays the calculation with a (correct) declination of -21.5° and a latitude of 52.5° instead of using the co-latitude of 90°-52.5° = 37.5°.

The correct graphical calculation looks like this:

Calculating ortive amplitude with a Sine Quadrant using sin(declination) / sin(co-latitude).

With a result of 37° for the ortive amplitude.

In order to make the calculation more legible, we can transform the equation and do this:

``````sin(ortive amplitude) = sin(declination) / cos(latitude)
``````

which looks like this:

Calculating ortive amplitude with a Sine Quadrant using sin(declination) / cos(latitude).

With a result of 90°-53° = 37° for the ortive amplitude.

Compare Tycho with a sunrise azimuth of 127° and thus an ortive amplitude of 127°-90° = 37°.

### Page 276, Eq. 25

The equation:

``````tan α_s = (sin τ / (sin φ · cos τ)) - cos φ · tan δ
``````

has to look like this:

``````tan α_s = sin τ / (sin φ · cos τ - cos φ · tan δ)
``````

Where an hour angle of 0° for noon yields an azimuth of 0°. For the azimuth from North, for a positive value of α_s subtract 180 - α_s and for a negative α_s add 180 + α_s.