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tony873004
2017-Aug-27, 10:48 PM
Florence is a miles-wide asteroid that will come within 4.4 million miles of Earth on September 1. That's very close for an asteroid this size.
On my twitter is an animation and a link to a simulation of Florence as viewed from Earth. It comes from the southern sky and disappears to the north.

https://twitter.com/tony873004/status/901883012589150208

George
2017-Aug-28, 09:44 PM
Nice Tony! It looks like she will be a night time event, though I assume no gail is expected. ;)

I calculate an apparent mag. of about 6.2, slightly brighter than Ceres. [I'm curious if my calculations are correct, and it won't shock that I'm off.] I assumed a 0.09 (Ceres) albedo for Florence.

tony873004
2017-Aug-28, 10:04 PM
JPL Horizons shows it peaking at 8.65 from Aug 30 20:20 to Aug 31 08:10.
This is before close approach, probably because of the phase.

DaveC426913
2017-Aug-28, 11:07 PM
Too dim for naked eye. :(

Anyone know what its disc will subtend at closest approach? Will it appear as more than a point in a modest scope?

(No, of course it can't. It can't manifest as a disc and have a peak mag of only 8 or so... )

My calcs give it a disc subtending a mere .14 arcseconds.

George
2017-Aug-29, 08:04 PM
JPL Horizons shows it peaking at 8.65 from Aug 30 20:20 to Aug 31 08:10.
This is before close approach, probably because of the phase. Yep, I erroneously used miles instead of km and I did not adjust for the phase angle. I did see that Horizons shows an albedo of 0.23 for it. Doing these gives me an 8.5 mag. value, so I'm close.



My calcs give it a disc subtending a mere .14 arcseconds.Your value looks about right. I get 0.124 arcseconds.

DaCaptain
2017-Sep-01, 04:48 PM
Florence is a miles-wide asteroid that will come within 4.4 million miles of Earth on September 1. That's very close for an asteroid this size.
On my twitter is an animation and a link to a simulation of Florence as viewed from Earth. It comes from the southern sky and disappears to the north.

https://twitter.com/tony873004/status/901883012589150208

Nice animation, I don't have a scope so it's a great way for me to visualize it. It's nice having the constellations outlined so you can find it easier.

StupendousMan
2017-Sep-01, 07:08 PM
I'll be taking images of it tonight (Friday night Sep 1/Saturday morning Sep 2) in Rochester, NY, if the weather permits. The object is close enough that it will show easily measurable parallax from sites just a few hundred km apart. So, if anyone is interested in helping me out, here's what we could do.

My plan is (again, weather permitting) to take images of the object between UT 2017 Sep 02 03:00 to 05:10 or so. For parallax purposes, I'll take images starting at the top of the minute, for the first 10 minutes of every hour. In other words, I'll start exposures at exactly UT 03:00:00, 03:01:00, 03:02:00, and so forth, up to 03:10:00. I do the same for 04:00 and 05:00, if the clouds don't interfere. The asteroid is bright enough (roughly V = 9) that we'll only need to expose for 1-5 seconds, during which time the motion should not be significant.

If all goes well, any participating sites could share a list of the images they succeeded in taking, and we could pick a few good matched pairs of images, taken at the same time from different locations. Those images, plus a bit of trigonometry, could allow us to measure a rough distance to the asteroid. It's already known, of course, and to much better precision than we could compute, but this can make a fun little student project. A student with whom I collaborated some years ago wrote a short paper describing the details of the technique -- see

http://spiff.rit.edu/richmond/parallax/neo_parallax.pdf
(also at http://adsabs.harvard.edu/abs/2004AmJPh..72..264S)

That's a pretty complicated procedure, but one can ignore many of the details and make very simple estimates for the baseline distance, and still get pretty decent distances.

If anyone is interested, please let me know via PM or in this thread. I'm not sure we'll be able to see the skies tonight; I'll post an update later.

DaveC426913
2017-Sep-01, 09:45 PM
It'd be cool to participate, but alas, Clear Sky Chart (http://www.cleardarksky.com/c/MssssgaONkey.html?1) shows 100% overcast here in the GTA.

DaCaptain
2017-Sep-01, 09:49 PM
Will we pass through any debris from it? Hopefully there won't be any large stray pieces heading our direction.

DaveC426913
2017-Sep-01, 10:11 PM
Will we pass through any debris from it? Hopefully there won't be any large stray pieces heading our direction.

No. It's an asteroid, not a comet.

StupendousMan
2017-Sep-01, 11:14 PM
Actually, the weather is looking pretty bad here in Rochester, too. Ugh. I'll post one update around 9 PM
local time.

_If_ this doesn't work out tonight, maybe we can try something similar later. But let's keep our fingers crossed.

StupendousMan
2017-Sep-02, 01:09 AM
And ... it's cloudy in Rochester. Rats.

So, no observing for us tonight. I'll keep checking and maybe try again if it's clear during the next few nights.

ngc3314
2017-Sep-05, 01:27 PM
I was going to try this with an audience at DragonCon, simultaneously using Kitt Peak and Cerro Tololo.

Remnants of a tropical storm wiped out Kitt Peak after a clear week. At least I got some trails as well as tracked images to show "NEO!".

What might have been - here's similar observation of 2015 J025 from April 19 of this year. The one-minute trails do mismatch in brightness due to telescope apertures, and I didn't want to bring up the noise by balancing them more closely. Red=Chile, green=AZ.

George
2017-Sep-05, 01:54 PM
Very nice!! I don't recall seeing a better example of parallax in motion, so to speak.

antoniseb
2017-Sep-05, 02:10 PM
Did Arecibo or any other such facility manage to do their radar imaging trick? I'm looking forward to seeing how much detail they were able to show on the shape and surface of Florence.

Superluminal
2017-Sep-06, 05:56 AM
Seems that Flo has a pair of moons.
https://astronomynow.com/2017/09/05/radar-reveals-two-moons-orbiting-asteroid-florence/

schlaugh
2017-Sep-06, 09:47 AM
And with the noise removed.

https://www.youtube.com/watch?v=ywZ5DI96oM8&sns=em


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