View Full Version here: : June 22nd - Nix to Occult mag. 14.1 star
17-06-2010, 10:40 PM
I have just received word from Bruno Sicardy (LESIA, Observatoire de Paris) of the possible occultation of a reasonably bright star by Pluto's satellite, Nix.
This an alert for a possible stellar occultation by Pluto's small satellite, that could be visible from NZ and AUS, on 22 June 2010 around 09:55 UT (night 22/23 June), see map attached.
The star is red, and is about 1 mag *brighter* than Pluto in red (R=12.5).
Nix is small (100 km across), and uncertainties are of the order of +/ 1000 km, so the probability is low. But payoff could be high, and the observation does not take much time, at the beginning of evening, so that the dinner is not ruined...
Note that for observers with sufficiently large telescope, even a visual observation could be attempted, as the event will be sharp, with an easy nearby comparison "star", namely Pluto. Of course, video or CCD observations are useful in terms of light curve analysis.
I have created a feed for this event for users of Occult Watcher that have subscribed to the TNO extras feed. Alternatively the prediction plot can be seen here...
18-06-2010, 08:00 AM
All going well i shall attempt this one, i need some clear skies though!
18-06-2010, 09:00 AM
Good onya Chris.
Below is a FOV image from Bruno.
18-06-2010, 09:13 PM
It looks like it wont even be above the horizon for Perth - perhaps its just as well the forecast is for rain that night.
19-06-2010, 01:15 AM
On the case Dave - well placed from here, but rain forcast!
Did Bruno publish the angular separation between pluto and nix by any chance?
20-06-2010, 12:00 AM
I presume that 2UCAC 24917003 is also known as 3UCAC 144-303019:
18h16m57.00s -18°14'51.7" * 3UC 144-303019 mV:14.12 b-v: 0.00 pmRA:-0.005 pmDE: 0.003
What does "In the 1-sigma zone" mean?
I think I can figure out what "104 Km outside the shadow path" means.
21-06-2010, 12:56 PM
All predictions have a have a degree of uncertainity due to the position of the occulting body and the star. The first zone of uncertainity is called the 1-Sigma, the next 2-Sigma and so on.
For this event, the star position is not actually derived from UCAC2 or 3 or whatever, it is defined by "The Rio Group" as coordinated by Bruno and is considered to be better than UCAC? because the astrometry is more recent. Also the position of Nix is based on offsets from Pluto that is also determined by Bruno. However for observational purposes we can use the UCAC2 number stated.
The predictions of Bruno have a higher accuracy than those determined via the latest Pluto ephemeris and UCAC?. This is shown by the Pluto positive observed in New Zealand earlier in the month. Using the standard methods, the shadow path was not predicted to cross the earth, but the observed positive was within the stated uncertainty of Bruno's prediction.
Anyway... below is a plot from Occult Watcher that shows the 1-Sigma.
21-06-2010, 11:14 PM
Mathematically, I assume a sigma is an actual reference to a standard deviation (the symbol sigma is used for the stddev). Since a standard deviation is related to a level of confidence for a particular population (or a certainty of a sample to be within a level of confidence), I assume that 1-Sigma is the equivalent of stating a level of confidence of 1-0.341 = 0.659 or a 65.9% confidence that the shadow will pass between the two red lines.
This doesn't sound correct to me though, as a standard deviation would actually result in a 68.2% level of confidence... can anyone clarify this?
21-06-2010, 11:35 PM
That's correct assuming a standard normal curve.
You have that variables of mean and variance to play with to alter those numbers. In reality the variance will be based on the geometric probabilities of the assumed asteroid orbit and size together with estimated stellar position.
It's way over my head!
23-06-2010, 09:39 PM
Frickin cloud, Mr Bradshaw....please accept my donation of cloud! LOL
BTW, i got my GStar to capture via my laptop with a $50 USB capture device (720x576 res)
and i can download the avi's to my DVR.
The beeper box idea with laptop time and GStar capture software is really great! Now all i need is to have a good mag 9 occultation to test it on!
23-06-2010, 11:33 PM
I have plenty of my own thank you Chris, I don't need any more...
Well done on the kit, and if you PM me your address, I'll send you something nice to add to your growing collection of electronics - providing you promise to give a talk at NACAA 2012!
(Dear readers, beware of internet grooming - only send your details to people you actually know;))
24-06-2010, 12:45 AM
I wondered what had happened over there, you've all been awfully quiet on the list so I'm guessing no one has seen anything positive.
27-06-2010, 01:00 PM
Yes. To the best of my knowledge, there was one observer in NZ who observed a miss, and the rest were clouded.
There was another Nix event that crossed Europe and that was mostly clouded too.
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