ANWEISUNGEN-FUR-DIE-PHOTOGRAPHISCHEN-AUFNAHMEN-DER-LEUCHTENDEN-NACHTWOLKEN - 103 YEARS ON - NOCTILUCENT CLOUDS

One hundred and three years ago, Jesse published the first manual for noctilucent cloud observing and gave details of measuring photographs to obtain accurate estimates of their heights. We give a brief review of the measurements published since then and discuss the different methods that have been used tor height measurement using pairs of photographs taken from ground level. Using the methods on data derived from two pairs of photographs taken in Scotland during the years 1983 and 1986 illustrates the deficiencies and advantages of the different methods. Our recommended method, the so-called 'surface' method, is adapted to the use of desktop computers. In it, the photograph from observatory A is redrawn in the field-of-view of observatory B by making an assumption about the height of the noctilucent clouds. The assumed height is altered until the form and position of the NLCs redrawn in Bs field-of-view match best the form and position of the NLCs observed from B. Also vice versa, that is to say the redrawing of B's NLCs into the field-of-view of observatory A. Since the selected height should be the same for both transformations, the statistics of the height estimates allow an estimate of the precision of the height estimates.