Occult Flash Tag

Erick Couto

About this app

This app uses the phone's flash to mark videos with high accuracy (milliseconds). It is mainly used for analog video cameras that do not have a device for timing the video while recording. The major use is for Astronomy Occultation events.

Just pick two schedules (UTC) prior to the event to be observed, a few minutes before and a few minutes later.

In time the camera turns on the flash and the CCD sensor coupled to the telescope will record a high-brightness frame (white) easily detectable later.

The precise time will be shown in the app after the NTP checking.


How to use:

1 - Start recording the video
2 - Set the start/end time in the app for a few minutes before the event (occultation).
3 - Place the device near the telescope tube (front), with the flash pointed at mirror.
4 - Press the start button and wait
5 - After recording the video, store the values shown in the app in the audit field.

Then just select the frames with high brightness. They will match the schedule indicated in the app, with millisecond precision.


The app is open-source (Apache License 2.0) and developers are welcome.

What’s new

- Inclusion of the link to the user manual on the "About" screen. (Ferran Casarramona)

- Compatibility with newer versions of Android

Bug fixed (Alexey V. Popov)

- Wrong calculation of start time inbetween of local midnight and UT midnight
- Changed settings did not apply before restart
- Flashes did not stop after stop button pressed

Settings extended:
- Repetition of flashes - 5 and 100 added
- Interval between flashes can be changed
- VNIITRI nt server added to the default list