IOTA Occultation Campaigns

Each year IOTA will identify at least two occultation events in North America as special observing campaigns for the year.  One event will be chosen for the potential to generate the most valuable results, and the other event will be chosen as the most “observable”.  We encourage IOTA observers to put these events on their calendar.  Given the high priority for these events, we expect some observers will travel to observe these events. Prior to each event, someone in IOTA will post messages to the Yahoo group informing everyone of the weather prospects and possible preferred locations for observers.

2019 May 1, 3:40 UT: (33128) 1998 BU48 Occults 11.4-mag. UCAC4 507-052412

Besides the campaigns described below, another important campaign is underway NOW for an occultation of an 11th-mag. star by a large (approximately 240 km) Kuiper Belt object with the expected path across the southern USA, southern Florida to southernmost California on Tuesday evening, April 30 local time. The event is of special interest since the object has an unusually large rotational light curve amplitude, indicating that it is likely highly elongated, perhaps a contact binary, similar to Ultima Thule, but about 7 times as large. A central occultation may last about 15s, but this is very uncertain since both the albedo and shape are unknown. The star is expected to subtend 11.5 km at the 35-AU distance of 1998 BU48. Consequently, the occultation events will be gradual, lasting 0.7s for a central event but more for grazing events. Unless the star is a close double, when occulted, the star will completely disappear for most observers since the object, at mag. 22, will be about 12 magnitudes fainter than the star. The occultation shadow will move from east to west, passing over s. Florida at about 3:45 UT, Texas at 3:47 UT, and s. Calif. at 3:49 UT. There is some uncertainty in the time, and since rings or satellites might occult the star, observations are desired for 10 minutes centered on the time for your location. Details are at . Working with the Southwest Research Institute (SwRI), which is coordinating both the astrometric updates for the prediction, and for observations, of this event, we plan to include it soon in the IOTA predictions and then in Occult Watcher, where local times and circumstances will become available. SwRI is keen to learn results of observations of this event quickly, to submit an abstract for a planetary science conference in the fall, but the deadline for submitting the abstract is May 7. So if you were able to observe the target star at the right time, please send a brief report of where you were and what happened, whether you had an occultation or not, to Leslie Young at, or fill out a google sheet at .

2019 May 11, 2-4h UT: The 39% sunlit Moon transits the Beehive

This is not a campaign event in the usual sense since it does not involve an asteroid, but it will be a highly-observable spectacle as dozens of stars, 6th-10th magnitude in M44 (the Praesepe or Beehive cluster) will be covered in rapid succession by the advancing dark edge of the fat crescent Moon. It will be best observed from the eastern half of North America. It will occur Friday evening, May 10th, local time. The graphic shows the Moon and M44 shortly before the occultation as seen from Greenbelt, MD, near Washington, DC at 10:00pm EDT of May 10th EDT. If you don’t already have IOTA’s free Occult 4 program, we recommend that you download it and generate detailed predictions for your location; for that, see . – information specifically for total lunar occultations starts near the bottom of p. 4. The date range described there will generate predictions for the whole year; for just this night of the Praesepe passage, use 2019 May 11 for both the start and end dates. Besides total occultations, there will be several northern-limit grazing occultations during the passage, with most of the events in the northeastern USA and southeastern Canada; for them, look under “May 11” (UT) at .

2019 Sep 26, 9:54 UT: (598) Octavia Occults 7.5-mag. SAO 80087

This occultation by (598) Octavia is the North American “most observable” event for 2019 since the prediction has good statistics with a medium-size asteroid visible along a path including many large cities across the USA. More details about the occultation can be found at and via OccultWatcher once the event appears there. Note that this occultation will occur about 5 days after the 2019 IOTA annual meeting at Camp Oakes in southern California. It was difficult to select the “most observable” event; some other very good events deserving observer’s attention are listed, with links for more information, at the bottom of this page.

2019 Oct 24, 6:08 UT: (16) Psyche Occults mag 10.2 star

This occultation by (16) Psyche is the North American “most valuable” event for 2019 since the asteroid, the largest metallic asteroid, is the target of a NASA mission, also called Psyche. More details about the occultation can be found at and via OccultWatcher once the event appears there.

Some other very good events during 2019

  • 2019 Aug 28 / (624) Hektor / mag SAO 10.7 over Monterrey, Brownsville, Miami, & Seville-ES is the largest Trojan asteroid, a contact binary object that also has a small satellite, so this is a runner-up for the most valuable asteroidal occultation of 2019

Last updated 2019 April 27.