Quaoar  17/02/2012

*See updates at the bottom of the page*

2012-02-17_Quaoar/2012-02-17T04.510_OPDstar_Quaoar.jpg

*See updates at the bottom of the page*
finding charts and maps (14/Feb)



Dark gray is night and light gray is astronomical twilight (Sun at less than 18° below the horizon).
Shadow moves from left to right, each red dot is separated by one minute, the nominal occultation time on the map, is for the big red dot, the closest approach
.
See finding charts bellow.
Doted lines are the estimated error of the star position, but the error can be bigger due to ephemeris offset!

The occultation is predicted to cross Europe from 04:31 to 04:34 Universal Time, but we advise to observe at least 10 minutes around this time.

Star J2000 coordinates:
RA  17 34 21.8453
DEC -15 42 10.586
Day coordinates:
RA  17 35 04.2368
DEC  -15 42 37.064

Star R mag 15.2
Star K mag 11.6
Magnitude drop in R 3.8
Max. duration if 1050 km  diameter 56 sec
 Max. duration for the satellite if 90 km 4.8s

Observation tips:

Absolute time accuracy is essential to connect together all the observations after the fact. Check the time of your computer with many sources (phone talked hour, different internet sites, ideally with a GPS). As images should be acquired for a long time (10min at least), its advised to check the registered time right after and right before the integrations, so if there is a drift, we can correct it by having the difference.

Beware of the dead time between the images. If you manage an exposure time of 1 sec (for example), but have a read time of 2 sec, then there is a 67% chance that you miss the dis(re)-appearance of the star. So it's better to have, say, a 4 sec integration, so you have  67% chance to get the occultation in one of your exposures.



Finding charts:

5 x 5 arc min FOV from DSS R band.
2012-02-17_Quaoar/field5x5arcmin_20120217_Quaoar.jpg


20 x 20 arc min FOV from DSS R band.
2012-02-17_Quaoar/field20x20arcmin_20120217_Quaoar.jpg
Click here to download a fits version of this image.


Finding charts in pdf format with magnitudes can be found on IOTA-ES web page [click here to access].



Astrometric Updates


With observations of the star performed from OPD (Itajubá/BR) in September 2011, Julio Camargo obtained a new position of the star.
With this new position and the offset obtained from the observed occultation, I obtained this map.
2012-02-17_Quaoar/2012-02-17T04.510_OPDstar_Quaoar.jpgupdated on: [09/02]

Zoomed version:
2012-02-17_Quaoar/2012-02-17_04.510_zStarOPD_Quaoar.jpg




Weywot, the Quaoar's satellite will also occult the star, but for observers in central Africa, according to IMCCE's ephemeris.
See below his track on Earth.
2012-02-17_Quaoar/2012-02-17_04.347_IMCCE_Weywot.jpg


Jean Lecacheux has made a zoomed map.
2012-02-17_Quaoar/12216WE_jpl21offRio1imcce1_OPD1_Weywot.gif