Lunar occultation to measure angular diameters

[jambouk]

I've been reading that lunar occultations of planets and other moons in our solar system was used in the 1960s and 1970s to measure the angular diameter of the moons of Saturn and Jupiter. But I wonder why not just use a micrometer?? Presumabely atmospheric seeing would impact on both methods equally, but using a micrometer would not require a lunar occultation event to be occuring.

Grateful for any thoughts.

James

 

[JamesF]

Accuracy, perhaps?  Let's say for the sake of argument that it were possible to time the occultation down to one hundredth of a second.  I think that would make it possible to measure angles to an accuracy of one millionth of a degree or thereabouts.

Or perhaps at the time the logistics of building a big enough micrometer to fly out to Ganymede and drop over it to measure its diameter was just too much for NASA to handle

James

[jambouk]

Thanks. 

What would be the minimum angular diameter a micrometer on a massive scope with excellent seeing could realistically measure then? I've converted your millionth of a degree into 3.6 milliarcseconds which is pretty amazing!

 

[JamesF]

Actually, it does also strike me that the reason might be far more prosaic.  For instance, perhaps they could build kit accurate enough, but didn't have sufficient funding.

I have to admit that I have no idea how accurately it could be done with some sort of micrometer arrangement.  I think it's an interesting question.  I know we have a few posters who are interested in occultation timing, so I'm hoping one of them can provide more details.

James