This classic publication dating back to early twentieth century contains all necessary and sufficient materials to be used for easy determining both centring and total errors of the sextants at sea. The book will provide readers with the angular distances between the starts of the second magnitude and they are considered suitable for the observations by means of sextant.
The method was used for correction of the sextant errors through observing the star distances used to be treated as fairly impracticable due to the complicated nature resulting from the aberration and refraction. The aberration is a source of error which was neglected and not dealt with in the past.
There are three methods used to avoid these problems, namely choosing the time what the starts are located on one vertical great circle, ascertaining this time, and restricting the couples of stars to the season when the respective distances would be unaffected.
In short, this publication will be useful to the people with the interest in celestial navigation. They will find lots of information here and this will be something quite difficult to be found in any other publications. Just have a look and save this one for reference.