Closest enounter yet?

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Pete
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Closest enounter yet?

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Friday, 12 Nov 2010 It’s the second night in a row we’ve got a clear sky and I’m out activating the dome by 18:00 hrs.

3838 Epona is a 5.2 km sized Apollo class asteroid presently .22 AU from Earth. It’s a relatively brilliant 14.5 magnitude making it a good early evening target when seeing isn’t at its best. Apparent motion is 10’/hr and uncertainty level is 2 out of 9. Imaged 10 sec with 20 sec between exposures, 2X2, -30C, 2 Hz starting at 19:10 hrs. Frames 1, 9 and 18 show dRA = +0.3’ and dDEC = +0.4’. Since the S/N ratio is averaging a relatively high 31, red magnitude is reported as 14.6

2010 RA147 is a 910 meter sized potentially hazardous Apollo class asteroid presently .34 AU distant, 19.1 magnitude, 2.2’/hr movement, uncertainty level 5. Imaged 3 min, 2X2, -30C, 2 Hz from 19:57 hrs to 20:34 hrs. Using Astrometrica’s Track and Stack function, frames 1-2, 5-6 and 9-10 show dRA = +0.3’ and dDEC = -0.1’

2002 VE68 is a 524 meter sized potentially hazardous Aten class asteroid presently 4.3 million miles out. It’s bright at 15.6 mag, but moving fast at 12’/hr. Imaged 10 sec with 20 second delays between exposures, 2X2, -30C, 1 Hz from 20:47 – 20:58 hrs. There’s a neat little 13.9 magnitude S shaped spiral galaxy (UGC128000) in the image. Frames 1, 5 & 13 show dRA = -3.4’ and dDEC = -8.5 min. That’s pretty far out for something with an uncertainty level of only 2.

2010 UE51 is a tiny 15 meter sized Apollo discovered on Oct 29th. It’s only 650,000 miles out and certainly the closest asteroid that I’ve attempted to image. Current magnitude is 18.1 and motion is 12.3’/hr. Uncertainty level is only 5 out of 9. Imaged 30 seconds, 2X2, -30C, 5 Hz. From 21:09 – 21:59 hrs. Using Track ‘n Stack, here’s frames 12-16:

Image
The 15 meter sized asteroid is the bright spot a bit up and left of center, just below the bright tracked star.

Astrometry using frames 2-6, 12-16 & 19-23 show dRA = 25.9’ and dDEC = +5.7’. WOW! Something’s screwy here. My astrometry is accurate and Guide 8 shows UE51 to be where it is. But Astrometrica’s calculated position is far off. Apparently there’s a bug in Astrometrica.

Asteroid 75314 is an 18.3 magnitude asteroid in the same frame as UE51. It’s presently 1.5 AU distant, moving slowly at 38”/hr. Uncertainty level is only 1. Using Track ‘n Stack with the new movement and direction, frames 3-8, 36-41 and 69-74 show dRA = -0.0 and dDEC = +0.0

2010 VN98 is a 262 meter sized Amor discovered Nov 8 (4 days ago). As expected, uncertainty level is a high 8 out of 9. Present distance is 10.8 million miles, magnitude is 18.4, and movement is 10.5’/hr. Imaged 30 sec, 2X2, -30C, 1 Hz, starting at 22:27 hrs. Using Track & Stack, frames 1-4, 11-15 & 19-22 show dRA = +0.5’ and dDEC = +1.1’

91995 in the same frame as VN98. It’s a 19.2 magnitude asteroid 1.9 AU out. Movement is 32”/hr. Since exposures are only 30 seconds there’s a question as to whether I can capture this object even with Track & Stack. Frames 1-10, 12-21 and 27-32 show dRA = -0.0, dDEC = +0.0. S/N got as low as 4.7 in the final set but stacking did work.

2010 UX6 is a 166 meter sized Amor discovered on Oct 27th. It’s presently 3 million miles out shining at 16.5 mag and moving 18.3’/hr. Uncertainty level is 6. Imaged 10 sec, 2X2, -30C, 2 Hz from 23:11 to 23:23 hrs. Frames 1, 5 & 8 show dRA = +3.5’ and dDEC = +0.5’.

It’s late and I’ve got an early morning ahead so everything’s shut down by 23:30 hrs.

Conclusions & lessons learned:

While Lou and I visually observed a very near earth pass 3 or 4 years ago, getting down to only 15 meters in size is probably an observatory record.

Last night’s slewing problem has not reoccurred, and I suspect that the observing chair was in the way of the camera during the problem slew. All data was transmitted to the MPC before midnight.

hgp 15 Nov 2010 21:09 hrs.
Pete P.
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Rotorhead
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Re: Closest enounter yet?

Unread post by Rotorhead »

Good Lord, Pete!!! An object not much bigger than a house, imaged at nearly three lunar distances. WOW :shock: I'm certainly impressed!
Bob M
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BobSikes
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Re: Closest enounter yet?

Unread post by BobSikes »

Nice going Pete!

That little sucker is zipping along. I wonder what it's speed relative to earth is?

BobS
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NGC7000
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Re: Closest enounter yet?

Unread post by NGC7000 »

This is amazing, Pete.

Tom
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Pete
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It's gravity, dummy

Unread post by Pete »

An explaination for Astrometria's overlay position error provided by the software's author:

Note that Astrometrica does not include planetary perturbations in the calculation, while Guide does. For NEAs passing close to the Earth, this can make quite some difference.

The known object overlay in Astrometrica is intended for identification purposes, and for that, unperturbed positions are sufficient, except in the extreme cases of very close encounters. Do not use this feature to judge the quality of your observations.

Herbert Raab
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