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Hi, Jonny,

When measuring the lunar distance from the Jupiter there are two options how to make contact between the Moon’s limb and the planet. You can make contact between the Moon’s limb and the center of Jupiter or you can make contact between Moon’s limb and Jupiter’s limb. The later is possible when powerful telescope is used and you can distinctly see the limb of the Jupiter. This case is similar to the Sun’s lunar, when Sun’s SD is involved. In this case Jupiter’s semidiameter is used insted of the Sun’s SD. According to my experience if this method is used, a light shade should be used on Jupiter because the bright light spot of Jupiter seems much larger than it is in reality. After I found that,  I mostly use Jupiter’s center as a reference (but I use shades also in this case). This is why I asked you about the shades. Some years ago I could not understand why my Jupiter lunars when Jupiter’s limb was used were erroneosly.      

Some words about paper methods. When I need to find out how accurate my measurements are I use Frank’s  online lunar calculator. But when I want to feel how historic lunars were done, how difficult and time consuming the calculations were- I use different historic paper methods. I like to study them, compare and find the advantages and disadvantages of different methods.

I have not found any method that can be performed  faster than Thomson’s method. But this method does not allow correction for actual preasure and temperature.

When I want to get maximum accuracy from cleared lunars I use Chauvenete’s method from the middle of 19. century (method was rarely practiced because it was not actual any more at the time it was published). This method is specific, but it includes all possible corrections (thermometer, barometer, SD compression, oblateness of the earth). Initially I did not accept this approach, but after printig the tables from pdf, I found that calculations can be performed fast enough and the accuracy is in top level.

I like Mendosa y Rios’s tables from the begining of 19 century (there are two different versions of  tables he developed  based on so called “rigorous” method).

I have tried Dunthorn, Borda, Thomson’s second method, Witchell etc.

Modris Fersters