When will Eclipses occur ? Working it out for yourself …

Using Published Predictions You could use the predictions on the BAA VSS web pages These are very useful if you want to know which stars will be in eclipse tonight The SAC elements, rather than the GCVS elements, have been used for these predictions because the SAC elements are more up to date

Predictions on BAA VSS web pages

Working it out yourself … Sometimes, however, you will want a list of predictions for an individual star For TV Cas, the SAC elements are : Epoch = (24)44602.4534 Period = 1.8125956 days Enter these in a spreadsheet and convert them to a date and time

C4 = MOD(A4+0.5,1) B4 = A4+0.5-C4-15019

Setting the date & time format However this results in a day count (since 1/1/1900) and a decimal fraction of a day Click on each cell in turn and select Cells from the Format drop down menu and convert them to the required format e.g. for the Date cell ….

Display the date as dd/mm/yyyy

Predicting later eclipses Predictions for later dates are calculated by adding multiples of the period 1980 was many orbits ago, so this first calculation adds 1000 orbital periods

A5 = A4 + 1812.5956

Exploiting Excel to repeat calculations Later predictions can be generated by selecting cell A5, clicking on its bottom right hand corner and dragging the mouse down column A …

Repeat the calculation for A6-A9

… and for columns B and C …

Add smaller multiples of the period after you reach the current date …

Avoiding Bias In practice, its best not to know the predicted time of mid eclipse to the nearest minute This can be aided by leaving column C as a decimal fraction Then multiplying this by 24 and using Format/Cells/Number to give the time to the nearest hour in column D….

D4 = C4*24