Neptune Occultation Campaign 2021 (NOC21)

Occultation by Neptune, Proteus and Despina (2021-10-07)

(Night of Oct. 6th to Oct. 7th)


On October 7th 2021, Neptune, its rings and two satellites Proteus and Despina will occult a mag 14.9 star. This page presents information about this occultation.

This is not a classical campaign:

  • Occultations by the entire system can only be done in the IR K band or using a CH4 filter,
  • Alternatively, the observations of the occultation by the rings and/or satellites should be made with narrow filters in the red.

We recommend that you make some tests on the target star and evaluate the SNR, before attempting to observe the event. A relatively high SNR is needed, along with the a good time resolution. Only tests will help you find the best compromise.

We have secured time on the largest telescopes, however we thought some of you might be equipped for a such a challenging event.

Animation of the occultation (Credit: Dave Herald)

The occultation was predicted using JPL DE435 and NEP095 for Neptune and satellites ephemerides and GaiaEDR3 for star positions. Uncertainty on the star position is around 0.2mas but the uncertainty on Neptune and its satellites positions is not given.

For questions, more information or if you plan to observe these occultations, please contact noc21[dot]lesia[at]obspm[dot]fr

Observation request

The following table provided the required timing recording for Neptune's atmosphere, rings and its satellites. Note that the uncertainty is unknown but is estimated to be few hundreds km for satellites, so observation outside the path are welcome.

Neptune's atmosphere + rings 05:55 to 07:35
Neptune's atmosphere only 06:15 to 07:20
Neptune's rings only (05:55 to 06:20) & (07:05 to 07:30)
Despina 07:15 to 07:30
Proteus 07:50 to 08:10

Occultation maps

By clicking on the map, you will find individual Lucky Star page with many information (including interactive map).

prediction map

Map for Neptune

prediction map

Map for Despina

prediction map

Map for Proteus

Occulted star

Star source ID 2633285513360476416
Stellar catalogue GaiaER3
Star astrometric position in catalogue (ICRF) 23 28 17.8771 -04 41 40.598
Star astrometric position with proper motion (ICRF) 23 28 17.8846 -04 41 40.626
Star apparent position (date) 23 29 25.3090 -04 34 28.295
Proper motion μRA* = (19.2 ± 0.0)mas/yr; μDEC = (-4.9 ± 0.0) mas/yr
Source of proper motion GaiaER3
Uncertainty in the star position RA* = 0.2 mas; DEC= 0.1 mas
G magnitude 14.9
RP magnitude (source: GaiaER3) 14.3
BP magnitude (source: GaiaER3) 15.3
J magnitude (source: 2MASS) 13.6
H magnitude (source: 2MASS) 13.2
K magnitude (source: 2MASS) 13.1
z magnitude 14.5
z' magnitude 14.6

Sky map (Aladin)

link to sky-map
For declination above -25 °, Pan-STARRS survey is displayed by default whereas below -25 °, DSS is displayed.