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One night only 2021 VC7
#1
The minor planet 2021 VC7 is predicted to reach 15.8 mag tonight, moving at ~11"/sec from SE to NW through Andromeda around midnight EST.

Good hunting,

Phil S.
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#2
Thanks for the heads up. While our team was concentrating on 2019XS, we completely ignored the 3x faster mover 2021 VR2 in Taurus. How I missed that, I do not know. I've found a new way to plot these so they don't escape. See my post on Imaging XS.

WOW!. That rock gets to really start screaming around dark (3'/min) and then by midnight jumps to 20'/min when high up in the west. Still out of my reach visually. Will pass to our team.
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#3
Two of our Texas guys should have the weather to image VC7 tonight. 5" Tak and 8" Celestron. Phil, thanks again for the alert. This desktop has been busy but I missed it completely.
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#4
I saw it on the CNEOS list, but it wasn't in my download of the NEAs at Today's Epoch that I did yesterday. I did the download again this AM & I'm glad that this one looks like a winner.

With only 27k MPs in the MPC's NEA category, processing doesn't take too long. An additional 70+ MPs were added in today's list though.

The MP DBPS found 68 objects that will have Re<0.05 AU on Nov 13. Fortunately most of them were <0.05 AU on Nov 11 & 12, so not too many new ones to check.

Phil S.
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#5
I just came in from an exercise to hunt 2021 VC7, knowing it was too faint for the 13". The skies were about as good as they ever get here 100 miles from the gulf coast in SE Texas. 49F dew point 44, Precipitable water 11.05mm, 20.33SQM. Just doesn't get better. I was able to revisit a few friends - NGC 1055, 1073, & M77.

It will be interesting if the elements get updated later today as the current uncertainty is 8.
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#6
They did update the elements....

About 20 observations have been added, so the uncertainty has dropped from 8 to 7. The orbital elements have changed. Producing an error of ~1.4' in space during closest approach over previous plotting. Enough to elude when near the limit of visual observation. Was moving ~20'/min producing a four minute track covered 1.375° but very low in the NW. Kinky stuff!

It has an orbital period of 4 years and an aphelion distance out near Jupiter.


.txt   vc7 new and old.txt (Size: 352 bytes / Downloads: 1)
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#7
Hi BMD,

Sorry you missed 2021 VC7. Question: Your file shows the Mean Anomoly (M) with a negative value. Is the MP moving in a retrograde orbit, or did they think that it was? I don't recall seeing a negative M before. That's a pretty big change from -10 to +6.

Phil S.
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#8
From Wiki: In celestial mechanics, the mean anomaly is the fraction of an elliptical orbit's period that has elapsed since the orbiting body passed periapsis, expressed as an angle which can be used in calculating the position of that body in the classical two-body problem.

Horizons expresses mean anomalies in the range 0 to 360 degrees, whereas specialty software can sometimes express mean anomalies in the range -180 to +180 degrees, so that (for example) 351.63 degrees in Horizons is equal to -8.37 degrees. If you see a negative mean anomaly, just add 360 degrees to compare it to the figure in Horizons.

I get a lot of my elements from https://minorplanetcenter.net/db_search.

I thought that was a big change also. As I said, it made a large position delta (~1.4') at closest approach (<0.5LD) at my house @ 7:48UT Nov. 12. A large enough change (1.3'w and 16"s) to confound a visual sighting when at the limit of conditions and aperture.

I've retained both sets of elements should you like to see them.
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#9
Does MPC use the 0° to 360° format like JPL?

Thanks for the link to MPC.

Phil S.
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#10
Yes, the MPC uses that format.

In the hyperbolic case, the only sensible way to label mean anomalies is from minus infinity to plus infinity, with zero being perihelion. Negative MAs are when the object is approaching and positive MAs are when the object is receding. I guess that most astronomical products don't have to worry about the hyperbolic case.

Mean anomalies don't indicate prograde or retrograde motion, however they're expressed. If you're interested in whether an object is prograde or retrograde, you need to look at the inclination. If it's less than 90 degrees it's prograde, and if it's more than 90 degrees it's retrograde.
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