Occultation by Neptune of UCAC4 440-126076
on 9th of October 2024
Neptune and its rings will occult the 11m4 star UCAC4 440-126076 on 9th of October 2024. The occultation will be visible over nearly half the earth, as can be seen here.
However, the star is about 3m6 magnitudes fainter than Neptune (11m4 versus 7m8). This makes the observation a very delicate one.
How can the intensity difference been reduced?
The star is only about maximum of 2 arcsec away from the Planet, in case the observation of the main body the target, Neptune has an diameter of only about 2.5 arcsec. To isolate the stellar image is very problematic, szintillation and other flickering as well as blurring of the object will make it nearly impossible, if the intensity difference can not be reduced.
A filtering technique combined with a special camera could reduce the difference down to about 1 mag. Neptune has a very broad and deep methane band with a considerable width, much broader than Jupiter or Saturn. This is caused by the lower temperature of its atmosphere.
This can be easyly seen in the spectra of Neptune, such as p.e. recorded 1994 by Erich Karkoschka (Icarus, 1994)
If a near infrared filter with transmission wavelengths longer than 850nm is used in front of the camera, the difference between star and Neptune comes down to about less than 1 mag.
However the quantum efficiency of many amateur used CMOS and CCD cameras in this range is low, from about 30% at 850nm to about a few percent at 1000nm. But a special CMOS chip IMX462 (SONY) can be used. It delivers at 850nm a quantum efficiency of 60% and at 1000nm of about 30 percent. This increases the signal strength drastically. Such kind of camera is p.e. the QHY462C or QHY462M. The color version 462C can be used in this wavelengths range very well, because the transmission curves of the built in Bayer's grid in front of the chip is for these wavelengths the same for all colors. It can therefore be handled as a monochrome chip.
But keep in mind, if you can image the disappearance or reappearance of the star in Neptune's atmosphere, it would be a wonderful success. To see any dis- or reappearance ot the star by the rings it will not be easily possible, the optical density of the rings is very low, maybe too low without a K-Band camera.
The star
GaiaDR3
Star astrometric in catalogue (ICRF) 23 53 34.8023 -02 08 27.031
Star astrometric with proper motion (ICRF) 23 53 34.8065 -02 08 27.136
G magnitude 11.4
RP magnitude (source: GaiaDR3) 10.7
BP magnitude (source: GaiaDR3) 12.0
K magnitude (source: 2MASS) 9.1
RUWE (source: Gaia) 1.45
Generated by "The Neptune Viewer Tool" PDS Ring Moon Systems Node
a movie has been made, which shows the ongoing occultation with steps of 4min.
Disappeaance and reappearance times for Neptune and its rings for some European cities
Occultation of UCAC4 440-126076 by P8M00 Neptune on 2024 Oct 9
Disappearance and reappearence times for Neptune and its rings
Calculated by OCCULT 4
Location Long. Latit. Adams Arago Lassell Leverrier Galle D R Galle Leverrier Lassell Arago Adams
o ' o ' h m h m h m h m h m h m h m h m h m h m h m h m
Algiers, Algeria 3 5. 36 45. 0 14.7 0 18.0 .. .... .. .... .. .... 0 18.6 0 48.7 1 2.3 1 10.1 1 11.5 1 12.9 1 16.2
Amsterdam, Netherlands 4 55. 52 25. 0 16.6 .. .... .. .... .. .... .. .... 0 19.2 0 48.1 1 2.1 1 10.3 1 11.8 1 13.3 1 16.7
Athens, Greece 23 45. 37 55. 0 13.0 0 16.3 .. .... .. .... .. .... 0 17.4 0 48.0 1 1.6 1 9.2 1 10.6 1 12.0 1 15.3
Barcelona, Spain 2 5. 41 25. 0 15.4 0 18.7 .. .... .. .... .. .... 0 18.9 0 48.5 1 2.3 1 10.2 1 11.6 1 13.0 1 16.4
Beograd, Serbia 20 35. 44 45. 0 14.3 0 17.6 .. .... .. .... .. .... 0 18.0 0 47.9 1 1.7 1 9.6 1 11.0 1 12.4 1 15.8
Berlin, Germany 13 5. 52 25. 0 16.0 .. .... .. .... .. .... .. .... 0 18.8 0 47.9 1 1.9 1 10.1 1 11.5 1 13.0 1 16.4
Brussels, Belgium 4 25. 50 45. 0 16.4 .. .... .. .... .. .... .. .... 0 19.2 0 48.1 1 2.1 1 10.3 1 11.8 1 13.2 1 16.6
Bucharest, Romania 26 5. 44 25. 0 13.8 0 17.2 .. .... .. .... .. .... 0 17.7 0 47.8 1 1.6 1 9.4 1 10.8 1 12.2 1 15.6
Budapest, Hungary 19 5. 47 25. 0 14.8 0 18.2 .. .... .. .... .. .... 0 18.2 0 47.9 1 1.7 1 9.7 1 11.2 1 12.6 1 16.0
Casablanca, Morocco - 7 35. 33 35. 0 15.5 0 18.7 .. .... .. .... .. .... 0 19.3 0 49.2 1 2.9 1 10.6 1 12.0 1 13.4 1 16.7
Copenhagen, Denmark 12 35. 55 45. 0 16.5 .. .... .. .... .. .... .. .... 0 19.1 0 47.8 1 1.9 1 10.2 1 11.7 1 13.1 1 16.6
Dublin, Ireland - 6 15. 53 25. 0 17.6 .. .... .. .... .. .... .. .... 0 19.9 0 48.3 1 2.3 1 10.8 1 12.3 1 13.7 1 17.2
Frankfurt, Germany 8 35. 50 5. 0 16.0 .. .... .. .... .. .... .. .... 0 18.9 0 48.0 1 2.0 1 10.2 1 11.6 1 13.1 1 16.4
Glasgow, Scotland - 4 15. 55 55. 0 17.7 .. .... .. .... .. .... .. .... 0 19.9 0 48.2 1 2.2 1 10.7 1 12.2 1 13.7 1 17.2
Goteborg, Sweden 11 55. 57 45. 0 16.8 .. .... .. .... .. .... .. .... 0 19.2 0 47.8 1 1.9 1 10.3 1 11.8 1 13.2 1 16.7
Granada, Spain - 3 25. 37 5. 0 15.4 0 18.7 .. .... .. .... .. .... 0 19.1 0 48.9 1 2.6 1 10.4 1 11.8 1 13.2 1 16.5
Hamburg, Germany 9 55. 53 35. 0 16.4 .. .... .. .... .. .... .. .... 0 19.1 0 47.9 1 1.9 1 10.2 1 11.7 1 13.1 1 16.6
Izmir, Turkey 27 15. 38 25. 0 12.8 0 16.1 .. .... .. .... .. .... 0 17.3 0 47.9 1 1.5 1 9.1 1 10.6 1 11.9 1 15.2
Kiev, Ukraine 30 25. 50 25. 0 14.6 0 17.9 .. .... .. .... .. .... 0 18.0 0 47.6 1 1.5 1 9.6 1 11.0 1 12.4 1 15.8
Lisbon, Portugal - 9 15. 38 45. 0 16.2 0 19.6 .. .... .. .... .. .... 0 19.6 0 49.0 1 2.8 1 10.7 1 12.2 1 13.6 1 16.9
London, England - 0 15. 51 35. 0 16.9 .. .... .. .... .. .... .. .... 0 19.5 0 48.2 1 2.2 1 10.5 1 12.0 1 13.4 1 16.9
Madrid, Spain - 3 45. 40 25. 0 15.9 0 19.2 .. .... .. .... .. .... 0 19.2 0 48.8 1 2.6 1 10.5 1 11.9 1 13.3 1 16.6
Naples, Italy 14 15. 40 55. 0 14.2 0 17.5 .. .... .. .... .. .... 0 18.1 0 48.2 1 1.9 1 9.7 1 11.1 1 12.5 1 15.8
Oslo, Norway 10 45. 60 15. 0 17.2 .. .... .. .... .. .... .. .... 0 19.4 0 47.8 1 1.9 1 10.4 1 11.9 1 13.4 1 16.9
Paris, France 2 25. 48 55. 0 16.3 .. .... .. .... .. .... .. .... 0 19.2 0 48.2 1 2.2 1 10.4 1 11.8 1 13.3 1 16.6
Pic du Midi, France 0 5. 42 55. 0 15.8 .. .... .. .... .. .... .. .... 0 19.1 0 48.5 1 2.4 1 10.3 1 11.8 1 13.2 1 16.5
Prague, Czech Republic 14 25. 50 5. 0 15.5 .. .... .. .... .. .... .. .... 0 18.6 0 47.9 1 1.8 1 10.0 1 11.4 1 12.9 1 16.2
Riga, Latvia 24 5. 56 55. 0 16.0 .. .... .. .... .. .... .. .... 0 18.7 0 47.6 1 1.6 1 10.0 1 11.5 1 12.9 1 16.4
Roma, Italy 12 25. 41 55. 0 14.5 0 17.8 .. .... .. .... .. .... 0 18.3 0 48.2 1 1.9 1 9.8 1 11.2 1 12.6 1 15.9
Stockholm, Sweden 18 5. 59 25. 0 16.7 .. .... .. .... .. .... .. .... 0 19.1 0 47.7 1 1.7 1 10.2 1 11.7 1 13.2 1 16.6
Warszawa, Poland 21 5. 52 15. 0 15.4 .. .... .. .... .. .... .. .... 0 18.5 0 47.7 1 1.7 1 9.8 1 11.3 1 12.8 1 16.2
Wien, Austria 16 25. 48 15. 0 15.1 .. .... .. .... .. .... .. .... 0 18.4 0 47.9 1 1.8 1 9.8 1 11.3 1 12.7 1 16.1
Zagreb, Croatia 16 5. 45 45. 0 14.8 0 18.1 .. .... .. .... .. .... 0 18.3 0 48.0 1 1.8 1 9.8 1 11.2 1 12.6 1 16.0
Zurich, Switzerland 8 35. 47 25. 0 15.6 .. .... .. .... .. .... .. .... 0 18.8 0 48.1 1 2.0 1 10.1 1 11.5 1 13.0 1 16.3
