Astrophotography is one of those things you naturally assume must be pretty difficult; surely something so awesome requires years of practice and specialized equipment which costs as much as your car. You shake your fist at the sky (since you have given up on taking pictures of it), and move on with your life. Another experience you’ll miss out on.
But in reality, dramatic results don’t necessarily require sticker shock. We’ve covered cheap DIY star trackers before on Hackaday, but this design posted on Thingiverse by [Tinfoil_Haberdashery] is perhaps the easiest we’ve ever seen. It keeps things simple by using a cheap 24 hour clock movement to rotate a GoPro as the Earth spins. The result is a time-lapse where the stars appear to be stationary while the horizon rotates.
Using a 24 hour clock movement is an absolutely brilliant way to synchronize the camera with the Earth’s rotation without the hoops one usually has to jump through. Sure you could do with a microcontroller, a stepper motor, and some math. But a clock is a device that’s essentially been designed from the ground up for keeping track of the planet’s rotation, so why not use it?
If there’s a downside to the clock movement, it’s the fact that it doesn’t have much torque. It was intended to move an hour hand, not your camera, so it doesn’t take much to stall out. The GoPro (and other “action” cameras) should be light enough that it’s not a big deal; but don’t expect to mount your DSLR up to one. Even in the video after the break, it looks like the clock may skip a few steps on the way down as the weight of the camera starts pushing on the gears.
If you want something with a bit more muscle, we’ve recently covered a very slick Arduino powered “barn door” star tracker. But there’re simpler options if you’re looking to get some shots tonight.
Just a note if someone is going on the some-steppers-and-an-MCU version. You should turn it according to Sidereal time rather than 24hrs. That way you are turning with the sky rather than with the sun.
I am sure that 4 minute error is going to be the difference between the crap timelapses taken with this rig and the stunning professionally done ones. Way more important than finding somewhere dark, with a good view of the sky, using the correct focal length lens matched to a low noise sensor, having the axis of rotation accurately matched to the earths rotation, correctly applied postprocessing, etc…
OK you got me!
In the US it’s rather hard to find a 24 hour clock. However a cheap mechanical timer has the big dial and lots of torque to trip the switch and is 24 hour. Yes sidereal is right. I have wanted to have a lunar pointer clock. It has to go slower than 24 hour.
I imagine that you could easily change this to use a 12-hour clock movement by doubling/halving the size of one of the gears, right?
In principle sure, but that complicates things considerably. The beauty of this design is that the camera holder is just glued to where the hour hand would go. If you’re going to start printing gearboxes and stuff, you might as well just do it with a stepper.
Hi. I love just started looking into this stuff. I want to use something like this to point and rotate a home made antenna to follow visible iridium satellites. Any one k ow if this might work for that mission?
In the good old days we used to use the clockwork mechanism out of gas street lamps. This had lots of torque as it had to open a gas valve to light the lamp at the correct time of night and close it in the morning. They were also fairly easy to regulate to sidereal time by altering the adjustment on the balance wheel spring.