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Minor Planet (52768) 1998 OR2 Close approach
(2020-03-25, 03:42 PM)bigmasterdrago Wrote: The files that I see the elements for 1998 OR2 are unusual and MPCORB. If I understand it correctly, they have different epoch dates. Unusual is 2017 Sept 4, MPCORB is 2020 May 31. I seem to think that the ephemeris "start at" date should be near or at the epoch date for best position calculation. So it makes since to start at May 31, 2020 and run the ephemeris back to April 29th. Do I have this right? Or just run the ephemeris from Sept 4, 2017 using the elements in the unusual file. A rather long list.

Yes. The MPC has made changes that result in epochs far from when we are observing and I am not happy with it. Their standard epochs aren't close enough in time either. This is why ASTORB is often a better choice, but I understand it may not be updated at the moment.

The focus of the MPC is on near earth asteroids like this one, and I think if you asked them about it they would say that for other minor planets the inaccuracies are acceptable, and for NEAs they have special lists that are updated daily. So what you want to do is to download the MPC NEA Today list. I already used it when I added the most recent orbit to the Current Minor planets list.

Unfortunately, what we really would want to do in this case is to use the Single Minor Planet Download. But they use the "standard" epochs for those and the orbits can be up to 6-months off the current date. This ticks me off, to be honest. I have plotted asteroid position in Astrometrica and had them all over the place because of this.
Clear skies,
Head Dude at Skyhound

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RE: Minor Planet (52768) 1998 OR2 Close approach - by theskyhound - 2020-03-25, 04:06 PM

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