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Update 04 November 2010

The Eris stellar occultation
of 6 November 2010

On 6 November 2010 around 02:15 UT (night of November 5th to 6th, 2010), Eris may occult a red star with:
V ~ 17.1
R ~ 16.5
I ~ 15.2
K ~ 13.1
(see the Vizier output ).
The event could be visible from southern Europe, Africa, North, Central or South America (see updates below, though).

Astrometric J2000 position (Assafin et al, Rio de Janeiro group, Nov. 2009):

α= 01h 39mn 09.9257 sec
δ= -04d 21' 12.365"

The corresponding star apparent airless position of the day is:

α= 01h 39mn 45 sec
δ= -04d 17' 44"


Astrometric updates

We give below recent updates. Updates are also provided on Steve Preston's page

Notes:

- the shadow on maps below moves from right to left

- the larger dot is geocentric closest approach (corresponding to the time "h:m:s UT" given below the map)
- small dots are plotted every minute

- the width of shadow is 2400 km (assumed Eris' diameter)

- Eris' offset in ra and dec are given in the upper right corner of map, wrt the JPL#28 ephemeris

- the event may last for mor than 2 min

- Geocentric mid-time should between 02:10 and 02:20 UT, according to predictions. Europe will be ahead of that time interval by about 3 mn, and Americas will be 1-3 min after that time interval. So, it would be wise to observe +/- 20 mn around specific predicted times

- the star has V ~ 17.1, R ~ 16.5, I ~ 15.2, so that 1m-sized scopes are required. But if you think that you can make it with a smaller telescopes with a sensitive camera and several sec exposures, go for it!
(Remember that even with several sec exposures, usefull science can be derived: accurate size determination and detection of an atmosphere)

- if the download of your individual images is slow, say 5 sec, it is useless to have 5-sec exposures, as half the time will be lost in downloads ("dead times"). Then it is better to have, say 10-sec exposures or more, so that the probability that the dis(re)-appearance occurs during an exposure remains high.


18 October 2010: images taken at 1.2m Calar Alto, analyzed by J.L. Ortiz, R band:

Click on images for enhancement


25 October 2010: critical analysis by M. Assafin (Rio group) of Eris offset oberved since 2007.
Left: using R band data only from various telescopes, right: using broad band data images, showing that Dysnomia shadow could then go over the southern hemisphere. R band is better because it minimizes differential refraction. A caveat, however, is that less flux is then detected when compared to broad band, so that it is not clear which prediction is better:

Click on images for enhancement


30 October 2010: prediction by Steve Preston, based on images taken at Table Mountain by Bill Owen.
See this link

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01 November 2010: images taken from Cerro Burek (Argentina), analyzed by J.L. Ortiz. Left: R band, right: broad band:

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Images taken from Table Mountain (CA), analyzed by Bill Owen.
Left: 29 October, right: 02 November:

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Images taken from Table Mountain (CA), analyzed by Bill Owen.
Average of 29 October, 02 and 03 November:

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Left: from images taken at Calar Alto 3 November 2010, V band, analyzed by Jose Luis Ortiz.
Right: from images taken at Cerro Burek, 01-03 November, broad band, analyzed by Jose Luis Ortiz.

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05 November 2010: update by M. Assafin et al. 1.6m Pico dos Dias, Brazil

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Left: from images taken at Calar Alto 05 November 2010, analyzed by Jose Luis Ortiz.
Right: from images taken at Cerro Burek, 05 November, analyzed by Jose Luis Ortiz.

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left: 12.45x12 DSS2 (I band) arcmin chart
right: 8.2x7.9 arcmin 2mass K band FOV:

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