2010 EK139 15/07/2018

*Prediction based on Gaia DR2
2018-07-15-00.089_DR2_NIMAfeb18_2010EK139/2018-07-15_2010EK139/2018-07-15-00.089_DR2_NIMAfeb18_2010EK139.jpg

Observation tips:

- Shadow moves from **West to East**;
- The nominal occultation time on the map, corresponds to the big red dot, the closest approach.
- Each red dot is separated by one minute;
- Dark gray is night and light gray is astronomical twilight (Sun at less than 18 deg below the horizon);
 - *Absolute time accuracy is essential** (see important note below);

- Observations are requested from 00:00 to 00:10 Universal Time.   

After the observation, please fill the form available on this link (form), and send it to ribas(at)on.br.

Useful information:
Star J2000 coordinates:
  RA  13 51 37.298
DEC  -38 33 00.216
Day coordinates of the object:
RA  13 52 43.180
DEC  -38 38 30.881


2010 EK139 V mag 19.68
Star G mag 17.0
Star Rp mag 16.5
Star Bp mag 17.4
Star K mag 15.2
Magnitude drop in G 2.7
Maximum duration
 40 sec
Moon | 5% illum.
 @ 83 deg

Important note:
*Absolute time accuracy is essential**

to connect all the observations together after the fact. Check the time of your computer with many sources (phone talked hour, different internet sites, ideally with a GPS). 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 your camera takes 2 sec to read the image, then there is a 67% chance that you miss the dis(re)-appearance of the star. So it's better to have, for example, a 4 sec integration, so you have 67% chance to get the occultation in one of your exposures.

Finding charts from DSS:
  05 x 05 arcmin FOV (North is up, East is left)
2018-07-15_2010EK139/FOV_5x5_201807152010EK139.jpg

  20 x 20 arcmin FOV (North is up, East is left)
2018-07-15_2010EK139/FOV_20x20_201807152010EK139.jpeg



Predictions

Prediction from Lucky Star web page (i).
2018-07-15-00.089_DR2_NIMAfeb18_2010EK139/2018-07-15_2010EK139/2018-07-15_00h05m23s_2010EK139_GAIADR2pmGAIADR2_NIMAv4.png
(i) http://lesia.obspm.fr/lucky-star/predictions/single.php?p=5579
  Observations made on June, from Bosque Alegre, give the followig prediction provided by J.L. Ortiz.
2018-07-15_2010EK139/2018-07-15_bosquealegre-GAIADR2_2010EK139.jpg


 Observations made on early July, from Obs. do Pico dos Dias by B. Morgado and measured by J. Camargo, give a small offset of the TNO wrt NIMA ephem.
2018-07-15_2010EK139/2018-07-15-00.092_DR2_NIMAfeb18ofOPDjul_2010EK139.jpg

Please, see the observation tips at the top!