Occultation by Triton (2017-10-05)
: If you plan to observe, please download and read the protocol
in order to prepare the observation. It will help us to standardise the post-treatment. If you succeed in the observation, please fill the report (pdf
) and follow the instructions.
Information about the map:
- The straight and continue lines are the shadow limits considering the estimated radius;
- Each red dot is spaced by one minute, the nominal occultation time is to the big red dot (that is the geocentric closest approach);
- The arrow shows the direction of the shadow motion;
- The precision that mainly depends on the object is about 20 mas and can be down to the mas level for specific object such as Pluto or Chariklo (1 mas corresponds to 0.7 x Δ in km where Δ is the geocentric distance of the body in au);
- The star G* and J* are the G (from Gaia) and J (from 2MASS) magnitudes, normalized to a body moving at 20km/s in order to enhance very slow events;
- The body offset is at the upper right corner, if JPL ephemeris is used;
- Areas in dark grey correspond to full night (Sun elevation below -18 degrees) and areas in light grey correspond to twilight (Sun elevation between -18 and 0 degrees) while daytime is in white;
- Be careful, the dates are from the moment of the event in Universal Time, the night of the event may begin at the date before.
|| 2820 (including atmosphere)
|| 2017-10-05 23:51:24
|| 22 54 18.4364 -08 00 08.318
|| release of three preliminary Gaia DR2 stellar positions
|| μRA*=27.51mas/yr, μDE=-1.82mas/yr
|| 22 54 18.4346 -08 00 08.109
|| JPL nep081 + de435 + offset (RA* = -5.3mas; DEC = -4.8mas)
|Geocentric distance Δ (au)
: Offset for Triton's ephemeris was determined by Marcelo Assafin (Observatorio de Valongo) and his colleagues (Observatorio Nacional de Rio de Janeiro) with 8 nights of observations during 15-23 September.
Sky map (Aladin)
Interactive Google Maps
The red line represents the centrality of the occultation.
The green lines represent the half-light level
where the star's flux will be reduced by 50%. The blue lines are the 1% stellar drop
(the theorical limit of detection of the occultation).
Each red pin is spaced by one minute and indicates the mi-time of occultation on the central path. The path goes from East to West.
By clicking on one place, you will have an infobox with :
- Coordinates: longitude and latitude;
- Δd: projected distance to the central line;
- mid time: mid time of the occultation at the selected place;
- duration: expected duration of the occultation at the selected place (assuming a radius of 1410km);
- Triton elevation: Triton's elevation above the horizon at the selected place at the mid time.
Note that the uncertainty of the event is estimated to be about 130km in distance and about 10sec in time
The following websites may be useful to prepare the occultation's observation: