Hi, I’m Dave Lane of Dave Lane Astrophotography, and Focus (note capital F) has been a focus of mine since I began in taking landscape astrophotography images four years ago. Last fall/winter I spent 100s of hours researching how to automate and computerize focus. I developed software, bought four different Windows based tablets so I could carry a PC in my backpack to digitally focus my Milky Way images.
I was looking for several things in my efforts. My goals were to make focusing a quick, easy and repeatable process. After hundreds of trials, brackets, stepper motors, belts, gears and software tweaks I failed. It actually worked, I tried using it one or two sessions and got outstanding focus out of the camera, but it was kludgy, hard to keep attached reliably and was neither quick nor easy.
So after 100s of hours and 1000s of attempts I set the concept of precise digital focusing aside.
The thought never left me, though, how to get accurate focus and the resulting superb star control that comes with it. I experimented further with Bahtinov masks and at one point even tried stretching fishing line over a filter to produce star spikes. I openly admit that one was a low point in my thought process, but I was desperate. There had to be a way.
You see I’m really picky when it comes to getting the focus exactly right. Having first learned to be an astrophotographer of deep space objects brought me a need for round, in-focus stars. I wanted stars that exhibited themselves like diamond dust scattered across black velvet. The deep space photography I had done demanded this of me in a way not easily understood by daytime photographers.
So as the 2016 imaging season wound down, my mind turned increasingly to solving this problem. It takes me 5 minutes or so before each shoot to get the focus just right. It’s a painful, slow process because of my need to get it perfect. I usually succeeded in very tight focus, but at times it was just off this much > <. Standing next to drops of 1000s of feet while doing this and giving total concentration to focusing was not only time consuming but dangerous.
So once the season was over my efforts got intense, it was time to solve the conundrum. This offseason I would overcome the hurdles that had plagued my digital focusing attempts. I went back to the Bahtinov mask idea, one that is very common in the astronomy community but not workable in the DSLR world. The question I asked myself was why was that?
It turns out after 100s of tests that the real issue is the amount of light that was blocked by the slots of the mask. So the slots needed to be much finer, and I assumed many more of them. It turns out I had at least part of that correct.
So without going into the finer details of the 187 different versions of the masks, at least the ones I remember making, I present you with a year and a half of research and the final product. Please use and enjoy it!
