Dietmar Büttner

Germany

A campaign to observe the disappearance of this wide double star at the dark lunar limb (DD) was organized by the author.
A total of 89 timings made by 45 observers from five countries was received. This is regarded to be a positive response. The number of observations reported from the particular countries is as follows: Czech Republik 38, Poland 18, Spain 17, Germany 14, Slovakia 2.

Among the 80 usable DD observations 48 timings were made visually and 32 timings were made with video equipment.

Eight video observations of the main star ZC 2118 (2.9m) displayed gradual events with 0.04-0.08 s duration. Two other video observers reported step events 0.04 and 0.06 s apart. One visual observer saw a gradual event.
Seven video observations of the companion ZC 2117 (5.3m) showed a gradual disappearance with typical durations of 0.02-0.04 s. One video observation indicated two steps 0.05 s apart. Two visual observers reported gradual events.
All other video and visual observations didn't reveal any indication for gradual or stepwise events.
ZC 2118 is a spectroscopic binary with 0.01" separation. According to the XZ80Q catalogue ZC 2117 also might be a close double star itself with components of equal brightness about  0.1" apart.

Residuals could be computed for a total of 80 timings. They were plotted against the Axis Angle. The visual inspection of the graphs shows that most observations seem to confirm each other, however seven observations resulted in very large residuals due to unaccounted errors.

Whereas the quality of the TIMINGS themselves seems to be good, the quality of the REPORTS is a catastrophe!
A considerable number of the reports were incomplete or wrong (false time scale, geodetic datum for station coordinates forgotten, personal equation for visual observations missed ...). Many report files contained format erros. Several observers didn't use the requested ILOC file format, but reported their results simply as prose text in their mails.
More than 60 such problem cases (67 % of 89 timings) were discovered and partly corrected by the author so that those observations could be processed at all. However, this caused many hours of additional unnecessary efforts to him!
Besides this, such incomplete and incorrect reports are a serious source of errors and reduce the value of the observations considerably.
Be aware that a good observation doesn't simply consist in deploying hightech video or GPS equipment, but also requires a considerable portion of astronomical know-how on the object or event which is observerd. Finally, please be conscientious in reporting your observation. Your report is your visiting card as observer. A bad report leaves some doubt one the reliability of the observation.
 
 
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