Multiple Positions Plotting

[bigmasterdrago]

Phil, your plan works well. I might suggest as a sub for the letter suffix, consider an epoch date annotation. Instead of 2019 XSb, make it 1110 0500. Meaning date (nov10) and time (05:00UT) of epoch. As you know what rock you're running, so no need for the 2019 XS. It appears to work for me very well, so a simple workaround/kluge. Only anomaly I've seen is that in the IA, the green cross does not change to an open blue target when hovering over the asteroid position unless I'm zoomed in to less than 12°. Even though the mag is 13.9, I have to right click the designation box to get to Object Info or zoom in..... no big deal.

[PMSchu]

Hi BMD,

I'm glad that you were able to input extra elements too. I didn't get any problems with the MP DB. I opened & searched it & the new entries appear to be correct. As far as labeling the element sets with a date&time designation, I'd rather keep the references to the object in the DB so I can find them again when it's time to delete them. If they're linked to the close approach date, it might be hard to find them again.

What I thought was a problem with the dates & times wasn't because both CNEOS & HORIZONS use UT. 

Stepping through the time on the IA is cool because it shows how the positions change for each set of elements with the change in time. The position difference from the Nov 3 elements from MPC yesterday to the elements for Nov 8 & 9 from HORIZONS are eye opening, as are the differences among the HORIZONS elements. Since the orbit for 2019 XS is well determined, I think this is due to the purturbations from the close approach. No single set of osculating elements can account for these changes.

As for getting the blue target circle, the target must be bright enough. Try changing the displayed magnitude of the MPs to a fainter magnitude. ST4 displays fainter objects as you zoom in. I've set my IA to display 11th mag at 30° field. At 5° field the mag limit is 14.6; however, the MPs are set to display 3 magnitudes fainter, so 17.6 mag.

2021 UO7 isn't in the list of MPs that were downloaded from MPC yesterday, so it's a new one.

Phil S.

[bigmasterdrago]

I found elements for UO7 in all three databases. Some specialty software does not need an osculating element set as it makes its own elements as it processes the time steps individually. I have no idea where the mass comes from of the small rocks, but it has to know that in order to make those calculation. Horizons does it and no matter when the epoch is, it will get positions correct for any dates (Horizon/JPL). In ST, we need to input osculating orbital elements from Horizon near the position date.

Again, your idea works well. With no issues in the MP DB. Thanks for the genius concept.

[PMSchu]

Hi BMD,

Glad you like adding extra entries for close approaching MPs. If you entered extra entries for elements from different sources, how well did the computed positions compare? How about for different epochs of osculation? As my results demonstrate a different epoch of osculation results in a different predicted position even using elements from HORIZONS, as expected. I'm surprised by the amount of the difference. The position for the Nov 8 1800h elements is 16' 10" ahead of the position for the Nov 9 0900 elements. The time difference is ~16 minutes along the track.

I just downloaded the NEAs at Today's Epoch from the MPC. The elements for 2019 XS were updated, but the elements for the 2019 XSa-f entries were unchanged. 

2021 UO7 has been added to the DB, too. The DBPS found 71 MPs that will be <0.05 AU on Nov 7, 6 of which are the extra entries added for 2019 XS, so 65 MPs! Those things are everywhere.

The MP DB has accepted the extra entries for 2019 XS without causing any problems. This looks like a straightforward way to add additional epoch dates for any MP without having ST4 decide that the positions aren't different enough to retain the new elements.

Phil S.

[bigmasterdrago]

It's difficult to compare those positions with different epoch dates. The farther they get from any particular epoch date shows a higher error in position compared to that generated by Horizons of other specialty software designed for that purpose only. I'm sticking with the plan to generate charts (IA) prior to an attempted observation using only a single set of osculating elements from Horizons very near (2 hours) time of observation. Your plan works well to get the object plotted without disturbing the elements already stored in the MPDB. Works like a charm. Thanks again for the recipe.

My standard plan of attack is to keep a sharp eye on NEOS. Then use Horizons to get a pre-picture of circumstances (moon, daylight, altitude, phase, magnitude, etc.). Then shove the rock into ST4vPro or the specialty software to make real charts.

I fooled with 2019 XS just now and the epoch date from the MPC (July 4) and the epoch date from JPL (June 30) indicate a position difference of ~2.148" on Nov 9 21:00cdt. When I look at the Lowell position (epoch Oct 12), it appears ~14.5" to the SW of the other two positions. And although the epoch dates have not changed whatsoever, the elements have very slightly changed for a specific date. So their positions are somewhat different. If plotted tonight, they are much more in agreement, the Lowell outlier being only 6" out. But, and this is a big but, we have it plotted fully 34' SSW of the Horizons position. This simply emphasizes the need to always get osculating elements near the time of observation. Especially since this rock when close will be at the limit of my skies and scope.

I hope I'm making sense.

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I just downloaded the NEAs at Today's Epoch from the MPC. The elements for 2019 XS were updated, but the elements for the 2019 XSa-f entries were unchanged. 

Phil S.

I just did the same for 2019 XS and the element list now has an entry for Nov. 9.96, *not* Nov. 5.something. XS also has epoch dates of Oct 10.0, Mar 11.0 and 2020 Jul 23.0

But yet for 2019 XS1, it has an epoch date listed as 2021 Nov 5.0 as does 2019XT and dozens of others. So my question is why not one for todays date for 2019 XS??? Is this by design? Today is not the 9th!