OccultWatcher is a multi-platform system for supporting observations of astronomical occultations. OccultWatcher (OW) provides a dataset of accurate predictions for occultations; provides interfaces for searching the dataset of occultations; and provides tools which facilitate the coordination of observations of these occultations. With OW, observers can search for events to observe, determine the best location for observation an occultation, announce their plans to observe an occultation, and monitor the observation plans of other observers interested in the same occultation events.

OW Components

  • OccultWatcherCloud (OWC): OWC is a cloud-based database of event predictions, observer accounts, and observation planning.
  • OccultWatcher Desktop : Desktop Windows application for accessing with OWC predictions.
  • OccultWatcher Mobile Apps : Android and iOS apps for accessing OWC predictions. In progress, check the relevant “app store” for your platform.


  • Getting Started
    • Go to the OW Desktop page, download and install OW Desktop.
    • Setup a user account with OW.
    • Review the events and configuration information on the OW Desktop page, then configure your instance of OW Desktop.
  • Getting Help
  • Finding Events on OWC
    • OW Desktop is the easiest option for finding information on events which might be observed from your location. However, if an event has been tagged (see below), you can search for this event directly via the OWC Events Page. On the OWC Events page, enter the ID for the object (e.g. usually the asteroid number) and a date range for the event. The search function will return a list of all events in the date range which have been tagged.
  • Tags and Feeds
    • Occultation events in the OWC dataset may have multiple tags assigned to them. Various organizations, or individuals, tag events to advertise the event for other observers. For example, each year IOTA identifies a large set of events deemed to be particularly interesting and assigns the “IOTA” tag to these events on OWC.
    • OW Desktop users will select one or more “feeds” as sources of events which they wish to search and find events they may wish to observe. These “feeds” are directly associated with the tags in OWC. For example, the IOTA feed in OW Desktop pulls down all of the events in OWC which include the IOTA tag. The “Community Tags” feed in OW Desktop pulls down the events associated with several tags in OWC (generally any tag applied by an individual OW user).
  • Prediction Sources
    • OWC may list multiple predictions for an occultation event. OWC will select one prediction as the best prediction for an event and this “default” prediction will be the only prediction which appears in OW Desktop. However, observers may access the other predictions via OWC and they can change the default prediction for this event in their instance of OW Desktop.
  • Reporting Observations
    • Always report your observation through the default system for your IOTA world region. Some tags/feeds are associated with groups who are also interested in observation reports. If an observer is not funded by one of these organizations, the observer should always report observations to the IOTA regional system first, then report observations to other organizations.