A productive night

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Pete
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A productive night

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Thursday, 2 Dec 2010 It’s been wonderfully clear all day, and although the CSC and other forecasts are predicting cloud this evening the observatory’s opened and cooling down by 16:30. After a quick and early dinner I’m out and optimizing focus by 17:30.

2010 SD13 is a 1.1 km sized Amor now 18.6 mag, .3 AU out, moving 3.4’/hr. Uncertainty level on this recently discovered asteroid is 5. Imaged 90 sec, 2X2, -30C, 10 Hz starting at 17:50 hrs There’s excellent transparency as I’m catching it clearly in single images at only 90 sec. Frames 1, 4 and 7 show dRA = +0.9’ and dDEC = +0.4’

2010LF86 is a 2.6 km sized asteroid presently .4 AU distant, 17.1 mag, moving 1.8’/hr. Uncertainty level is 3. Imaged 90 sec, 2X2, -30C, 2 Hz from 18:22 – 18:53 hrs. Frames 1, 7 & 13 show dRA = +0.3’ and dDEC = -0.3’.

2006 VZ2 is a 757 meter sized Apollo that hasn’t been seen for 4 years since its last opposition. Attempts to date to reacquisition on a 2nd opposition have been fruitless to date. The MPC thinks that it’s 16.2 mag, 11 million miles distant and really screaming past at 12.8’/hr. At this speed 15 seconds is an optimum exposure but I don’t have darks/flats/bias setup for 15 seconds exposures are taken without. 15 sec, 2X2, -30C, 3 Hz from 19:02 – 19:10 hrs. It’s not in my FOV, so therefore it’s still lost.

2010 VY190 is a 953 meter sized Amor discovered on Nov 15th. Tonight it’s 18.4 mag, .34 AU distant, moving 2.1’/min. Uncertainty level is 7, and there are several other asteroids within the camera’s FOV. Getting greedy, I’m stretching the exposure to 3 minutes hoping to trade off possibly minor inaccuracy for one of the dimmer asteroids. 3 min, 2X2, -30C, 2 Hz starting at 19:24 hrs. The seeing’s bad – I’m viewing low and directly over my neighbor’s chimney. Frames 1, 6 & 14 show dRA = +0.2’ and dDEC = -0.3’

From the VY190 frame, 45022 is 4.8 km in size, 18.5 mag, 1.2 AU out, moving only .34”/hr. Uncertainty level is 1. Frames 1, 6 & 14 show dRA = -0.2 & dDEC = -0.0

From the VY190 frame, 51399 is 6 km in size, 19.0 mag, 1.7 AU distant, moving 34”/hr. Uncertainty level is 0. Frames 1, 6 & 14 show dRA = -0.1 & dDEC = -0.0 These single frames are very weak, down to a S/N ratio of as low as 3.7

From the VY190 frame 2008 CT90 is only 19.4 magnitude and I can’t pull it out even with stacks of 5.

2010 WP8 us a 1.7 km Amor discovered Nov 17th. Tonight it’s 18.1 mag, .4 AU distance, moving 1.5’/hr. Uncertainty level is 7 out of 9. Imaged 2 min, 2X2, -30C, 1 Hz from 20:40 – 21:26 hrs. Frames 1, 4 & 8 show dRA = -0.3’ and dDEC = -0.2’

150636 is a 10.4 km sized main belt asteroid in the same frame as WP8. It’s 19.3 mag, 2.6 AU distant, moving only 24”/hr. Uncertainty level is 1. Using track ‘n stack, frames 1-5, 8-12 & 13-17 show dRA = -0.1 & dDEC = -0.0

2006 VB14 is a 1.2 km sized Aten presently 15.7 mag, 12 million miles distant, screaming across the FOV at 6.5’/hr. Uncertainty level is 3. The sky’s still clear but VB14 is low in the NE and my neighbor’s Christmas decorations are reflecting in the dew shield. Imaged 30 sec, 2X2, -30C, 0.5 Hz starting at 21:43 hrs. Frames 1, 6 and 13 show dRA = +1.8’ and dDEC = -0.5’. This is pretty far off, but since learning that Astrometrica doesn’t account for gravitational permutations it may not be significant.

152978 is an 869 meter sized potentially hazardous Apollo presently 18.4 mag, .33 AU distant, moving 2.7’/hr. Uncertainty level is 1. Imaged 2 min, 2X2, -30C, 2 Hz starting at 22:08 hrs. Frames 1, 3 &5 show dRA = -0.2’ & dDEC = +0.6’

That’s it. The clouds haven’t shown up but I’ve been out for more than 5 hours and the 31°F air is getting to me. Plus tomorrow’s a work day.

Conclusions & lessons learned:

The Autostar hand control display was blanking out frequently. While replacing it with an extra it fell to the floor and the wire broke off. Apparently the cable was bad because there were no further problems with blank display. A second mechanical problem looms and is much more severe. While slewing east the AZ drive is jerking stop and go. I’d seen this once previously and erroneously attributed it to the drape over the camera catching on the observing chair. The jerking happened twice this evening 

Data on 9 separate asteroids was forwarded to the MPC immediately upon my coming inside. All in all a very productive session.
Pete P.
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Rotorhead
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Re: A productive night

Unread post by Rotorhead »

You are the stalwart one, Pete!! Wow, a productive night indeed.

Kinda scary to think that we could have four NEO's in one FOV, isn't it??? Good Lord, no wonder you are busy. :lol: I thought I was up on this subject until you began your research. Now I get more and more amazed every time I read one of your reports. Good job!
Bob M
15" f5 Starsplitter Dob/80mm Finder
5" Explore Scientific triplet APO on a Vixen Sphinx GEM
________
"He numbers all the stars, and calls each one by name." Ps 147:4
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BobSikes
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Re: A productive night

Unread post by BobSikes »

Hi Pete,

Nice work, and you are very hardy - Brrrrr!

I was wondering what you meant by "Astrometrica doesn’t account for gravitational permutations". Is it taking the last known coordinates and extrapolating to the current time without adjusting for planet etc positions? For some reason I thought the predicted positions were coming from the MPC or some other database.

BobS
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Pete
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Re: A productive night

Unread post by Pete »

Only my target was a NEO. The other asteroids in the FOV weren't NEOs.

Both Guide 8 and Astrometrica use the same MPC database - mpcorb.dat 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. For this reason Astrometrica's author cautioned me "Do not use this feature to judge the quality of your observations."

So I use Guide 8 for planning and targeting. The Astrometrica data is surveyed for consistency (3 observations over an arc minute or more of movement) but with NEOs closer than 0.1 AU actual positions frequently vary from Astrometrica's overlay. Gravitational perturbation of minor planet orbits is the real wild-card when it comes to possible earth impact.
Pete P.
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BobSikes
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Re: A productive night

Unread post by BobSikes »

Thanks Pete,

I got it. Each planet tweaks the orbit each pass. So for a NEO asteroid, its so important to confirm and correct as many asteroid positions as we can.

In case the tweak puts the orbit into dear old planet next orbit.

Bob
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Pete
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Re: A productive night

Unread post by Pete »

You got it Bob. Space is vast and the possibility of impacts would be negligable but for gravity. NEO orbits get twisted each time they interact with Earth, Venus and Mars. These interactions are predictable but you can't run the predictions through too many perturbations before they lose accuracy.
Pete P.
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