How is it determined when the GRS has transitted the meridian. Is it at first contact of GRS and meridian or is it when the GRS is halfway across the meridian?
My totally uneducated guess is that its the when the centre of the grs hits the meridian. Do you want times for both the leading and trailing edges of the grs hitting the meridian?
To the best of my knowledge (although I have no way of proving it) it would be when the centre of the GRS crosses the meridian. I guess it would be like when a constellation culminates - that time is taken when the centre of the constellation is on the meridian.
That's about how I saw it too. I do find it surprising though how difficult it has been for me to track down the information. It's kinda like trying to define a planet. Everyone knows what it is until someone asks for a definition and you find there isn't one Same thing with the transit of the GRS info.
Quoting from Muirden "The Amateur Astronomers Handbook":
".....the Spot is so large that it is not too easy to judge just when the centre is on the planet's meridian. The best method is to take three transits, for the p and f ends as well as the middle."
No details on how this data is reduced, but a variation of 12 seconds in rotation period for the GRS is noted, involving significant forces to speed up or retard this massive object that far.
How is it determined when the GRS has transitted the meridian. Is it at first contact of GRS and meridian or is it when the GRS is halfway across the meridian?
Hi Paul,
Suggest you email John McAnally, in Texas, who is the transit timings co-ordinator
at the Association of Lunar and Planetary Observers. His email address
is CPAJohnM@aol.com
Hopefully he will be able to assist with information as to the convention.
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Calling all Joop-guru's!
Same thing with the transit of the GRS info.
