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sunandsky equip.jpg

sunandsky equip.jpg

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Volker Bartheld 06-Dec-2013 15:55
AWESOME!!! I feel so useless now...
Lensrentals06-Nov-2013 13:25
This is the home brewed timer I used to make the solar eclipse sequence composite image. It isn't anything close to occupying the space between lens and camera, but my submission is really about the number of things in a long chain of planning, which all came in-between the camera and the subject... in a manner of speaking. :-)

The one thing I absolutely had to capture during the eclipse was the moment of central alignment where the moon silhouette was superimposed as perfectly as possible over the sun. What I needed was an interval timer that had more absolute time accuracy than anyone was selling. The starring role is played by the round blue daughterboard which holds a temperature-compensated ultra-precise real time clock that drifts less than one second per week. When I connect a GPS with a data port the clock sets itself to GPS time, meaning that it will be within microseconds of the atomic clocks at the heart of the GPS system. The largest uncertainty is the camera's shutter lag which for my DSLR is around 45 milliseconds. But even that can be accommodated.

The large green circuit board is my own design. The central brain is the little blue daughterboard, an Arduino Pro Mini. The Arduino coordinates the GPS and clock, drives the user interface consisting of pushbuttons and an LCD text display (the large red board), and finally, fires the camera shutter when needed via optical isolators. I taught myself the Arduino programming environment and Eagle CAD software to design the board and create the files for the board fabricator.

There is a menu-driven system to set the timing interval and the central time. Hit go and this takes care of all the rest while updating the status on the LCD including the countdown times until the next exposure and the event's central time. The clock fires off a precise timing pulse every 1 second. A few milliseconds later the microcontroller wakes up the camera then fires the shutter. With another program I wrote this converts into a timer for deep-sky astrophotography, handling sequences of sub-frames, dark, and flat frames.

Not shown are the lithium battery and charger which works off the USB programming port.
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