JDIY10 : Barn Door Tracker


An area of my photography that has been a bit stagnate has been my night photography. I've played around with light trails and multiple exposure since High School using a 35mm film camera. I recently saw a couple pictures from William Vrbasso that just took my imagination to the next level, on what can be accomplished and what equipment I might need to upgrade to achieve it. My next endeavor is to get Astrophotography images, and the first challenge I need to overcome is the rotation of the Earth. Enters the Barn Door Tracker project. Since I do not have an endless amount of funds, I wanted to find a cost effective way to get those pictures.

There are plenty of articles to help me get started, for better or worse, so I have read a lot of how to build one and how I wanted to include electronics in mine. Many that I saw had electronics but I wanted to add a level of intelligence to mine.

Nuts and Volts has a nice column in it, but it really comes down to how do I want to build it? Do I want to use a stepper motor, DC motor or hand crank? I went with Stepper Motor because of precise control. I want to also build one with a hand crank just to see what kind of clarity I can get. I have realized that many of the project using the electronics have plenty of bulky equipment to go along with it, and that is something I'm trying to avoid as well. Making it portable is a must for me. Ultimately I followed an article from Gary Seronik. He made one with a limited parts list and I was impressed with his results.

I learned all the settings to use in my D3200 to take advantage of the JJC remote I got. Now I just need to build the platform that I can attach the camera to, that will let me get the best shot of the stars. Im not expecting to get the best pictures because of the lens that I have, but I think I should be able to get a really good start. My goal is simple, get a shot of the stars with all the colors from other galaxies.

I started with the basic form in Gary's article and made changes that would fit the parts that I was going to use. I went with ½ inch plywood as my base, I opted to use metal gears instead of POM that Gary used because of cost. I found a set from aiau.co.ltd on Ebay for $12 instead of $20 or so for each from SDP. I wanted to use an Arduino for a project as I normally use a Propeller for all my projects. I used a Pro Mini Arduino Compatible . I found a 12V bi-polar stepper motor from StepperOnline, and started off using a L293 to control it, but quickly found there was an issue with vibration and noise as you can see from the video below.

I also saw a need for a couple springs to keep tension between the stepper motor and larger drive gear, also between the top and lower pieces of plywood; rising the top piece wasn't an issue but lowering or resetting it, would cause the drive gear to rise. I noticed while out, I could keep pressure on it and it worked great, and came up with the spring idea.

I ordered a A4988 Stepper Motor Driver Module from Envistia Mall that offers microsteps native to help with vibrations; the L293 isn't great for using ½ steps or anything other than full steps. I predict moving from a full step to a 1/8th or 1/16th step will help vibrations a great deal. I am running everything off a couple 3.7V Li-Ion batteries with a step-up to 12V for the motor since the draw isn't too much, and the L294 doesn't have any power management.

UPDATE as of 8/5/19

Testing confirms that the stepper motor regardless of how small the step creates a vibration is isn't going enough, even with stuff to dampen the vibration. I am going to go the standard DC motor route and just control it with a HB-25 or similar motor control that I already have. I have ordered the motor, and gear which should arrive by Aug 7th. I will re-create the bottom portion of the tracker and keep the same size pieces so the axis will be the same and I can use the same parts. I eagerly await it's arrival.

I have also upgrades my lens to a 50mm 1.8f Nikkor lens to grab a lot more light, and it's amazing how much light it grabs at 1.7f. I took it out about 30 miles out of town and it still pulled in all kinds of light from the surrounding area. I will need to go further if I want to get the picture I imagined but I'm well on my way.

Amazing work that inspires