Nexta

Exposure Timing

A lot of this project is based off New EXposure Timing Analyser (NEXTA): a GNSS-based precise timer, as presented in the wonderful paper Reaching sub-millisecond accuracy in stellar occultations and artificial satellites tracking[arvix] (local mirror) by authors K. Kamiński , C. Weber , A. Marciniak , M. Żołnowski & M. Gędek.

The goals are to design electronics and boards to make this easy to use.

• PCBs that can be easily assembled, and manufactured that allow for easy LED bar registration (By having Aruco markers for example).
  • This should also make it easy to sell kits for people who do not want to solder or hand wire their own.
• Software:
  • Binaries available for common desktop OS
  • Can automatically finds LED bar
  • Allow manually register LED bar
  • Decode each rows time
  • Generates timing info, real first exposure time, and time for any row (if rolling shutter camera). Recommends offset to be added to header/metadata.

Showing the simple GUI after time analysis has been run. Header delta is what should be added to the time stamp to make it more accurate.

License

Please note that individual files in the repository have different licenses. For example the NEXTA microcontroller code is under CC BY-SA 4.0 and the some of the analysis software is under the GNU GPL 3.

Brief Description

There can be delays, or accuracy issues between when the camera is told to start it's exposure and when it actually does. This can be important for time critical applications. Also of importance is the time difference for each row in CMOS cameras with a rolling shutter.

In particular the timing application originally of interest is imaging fast time critical astronomical events. Such events include, LEO satilite, astroid transits, fast NEOs.

A better introduction is described in the paper listed above.

Example usage

• Take your camera with a lens on it
• Put electronics (NEXTA) in front of camera, square, well focused.
• Take a intial well lit exposure used for LED bar registartion.
• After NEXTA gets GNSS lock and starts blinking, take short exposures in a dark area.
• Use analysis software to get timing info to see the difference between what is in header/metadata.

Project contents

• hardware - This includes 3d printed mount, PCB design files, and arduino firmware
• nexta_analysis - Software to try to automatically decode timing images
• nexta_html_decode_form - A simple web form to decode the LED pattern into a time.

Issues

There is a still a lot to do, this project is in it's early stages. Check out the issue tracker and, feel free to contribute.

Instructional Videos/Purchase complete NEXTA kits

• https://starsynctrackers.com/store/learn-nexta/ - Includes Arduino, assembled NEXTA Shield, GPS Moudle, GPS Antenna, Plastic Stand, and Micro USB Cable

Other Projects

If you are interested in this project, you may be also interested in the following.

• Project Pluto GNSS astrometry - Take GNSS satelites going across your frame. Since these positions are well known you can use this to get better timing (Probably up to 0.01s)