How I set These Up

[theskyhound]

Hi Greg,

What I meant by "speeding up the calculations" was the time to get the new MP DB ready to perform the calculations. Every time I add a new set of elements to the DB all the precalcs are performed. To add elements before, during & after the close approach, requires three passes through the Add Element routine followed by the precacls each time. Afterwards, there's no guarantee that the different elements will be incorporated into the MP DB, either if ST4 doesn't think they're sufficiently different. I don't know what criteria ST4 uses to make this determination, so the time is frequently wasted anyway.

Pareing down the # of MPs to speed up the calcs for close approaches means that functionality for general MP observing is reduced. The close approach stuff is cool, but I'd like to have the large database available, too. Not asking for much am I?  

I'll defer to BMD on how well the HORIZONS elements predict MP positions during observing. I've never been able to get the iTelescopes to pick up any of the MPs that I sent them after using output from ST4i's Scheduler. Not sure if that's due to inaccurate positions or insufficient exposure times. In trying to avoid trailing I think my exposure times are too short, so nothing is detected.

Phil S.

I have been trying to get this simple idea across about Horizons for quite a while now, but I'm not sure you guys have understood me: please keep in mind that Horizons can still have major errors in it, and it is even possible that the elements from another source could be more reliable, if that source includes more recent, or more carefully selected observations. There is still some art to deriving orbital elements from observations, especially if those observations are limited. Things like weighting the observations by assigning observational errors, and constraining results to be realistic. A computer can't do these things perfectly on its own. Not everyone using the same data is going to derive the same orbit. JPL has the computational power to update elements in real time to "now." That's great. But as far as I know, there is no transparency regarding the observational data that they are including, how it is being weighted, and how much human interaction there is in the process. The test is not: "how well does it match Horizons?" but rather "how well does it match my observations?"