Build This Barn Door Tracker Today, Take Stunning Shots Of The Galaxy Tonight

Think you need some fancy equipment to get stunning shots of the night sky? Surely those long-exposure shots that show the Milky Way in all its glory take expensive telescopes with complicated motor-driven equatorial mounts, right? Guess again – you can slap together this simple barn door tracker for a DSLR for a couple of bucks and by wowing people with your astrophotography prowess tonight.

Those stunning, deeply saturated shots of our galaxy require a way to cancel out the Earth’s movement, lest star trails ruin your long exposure shots. Enter the barn door tracker, a simple device to let you counter the Earth’s rotation. [benrules2]’s version of the tool is ridiculously simple – two boards connected by a hinge. A short length of threaded rod with a large handle passes through a captive nut in the upper board.

A little trig allows you to calculate how much and how often to turn the handle (by hand!) to counter the planet’s 0.25°/minute diurnal rotation. Surprisingly, the long exposure times seem to even out any jostling introduced by handling the rig, but we’d still imagine a light touch and a sturdy tripod would be best. Those of you with less patience might automate this procedure.

It seems a lot to ask of a rig that you could probably throw together in an hour from scrap, but you can’t argue with [benrules2]’s results. His isn’t the only barn door tracker we’ve covered, but it looks like the simplest by far and would be a great project to build with kids.

[via r/DIY]

18 thoughts on “Build This Barn Door Tracker Today, Take Stunning Shots Of The Galaxy Tonight

  1. Great idea. I wanted to build something like this forever. Could automate with some Arduino or such. I wonder how this works as a heliostat – having a solar panel point perpendicularly to the sun throughout the day for optimal efficiency?

    1. Unless the motion is computer controlled to compensate, barn door drives are suitable only for relatively short tracking times because the rate of movement of the camera changes as the hinge closes.

  2. I’ll be the analog guy. A geared down motor with a pot to adjust the supply voltage? We’re talking about milliwatts here. The up-side is an infinite amount of exposure time instead of just 5minutes.

    What’s a good source for ultralow speed gear motors? …old washing machine timers?

    1. Ran down to hardware store to try this out. Bought a $5 24hour mechanical wall outlet timer. Automatically makes one rotation every 24hours and has enough torque to rotate my camera with a counterbalance on the other end.
      Awesome. Can’t wait until tonight!

      1. Was also thinking a cheap battery-powered clock mechanism with only a 2:1 stepdown* gear needed to make the 12-hour/rotation into 24-hour/rotation.

        * I’m a software guy so I’m likely getting the ratio backwards or the term wrong. Wikipedia has some very nicely detailed articles on gears and gear trains, which I’ll read when I have a week to do so. :D

    1. Barn Door (or Scotch Mount) trackers are a fascinating subject for astro-photography inclined hackers. There are any number of websites explaining the mathematics of the system and the more or less complicated mechanical systems. The basic, hand turned system shown here can provide perfect results, more exotic systems (eg with the threaded rod curved into a circular arc) can provide longer accurate tracking times.
      I highly recommend this type of mount over a motorized equatorial mount because you can easily know every parameter of your system as opposed to a bought-in system where you know nothing unless you pay dearly for the mount.

  3. as far as i remember an, i think a M6 threaded rod rotated at 1rpm at the right distance does the job. i just stumbled upon a disco ball motor rotating at that speed for 2€. i’ll try it out these days. only problem is, you have to play around before it switches to CW or CCW.

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