How to Focus on the Stars at Night for Astrophotography
Learning how to focus to infinity at night as one of the first great humps along the astrophotography learning curve. The infinity mark on the lens will almost always be close, but not quite. The optics will change very slightly as the lens adapts to nighttime temperatures. You'll need to find your focus at night to.
Dan E.
STEP 1: Look directly into a bright light source.
No, not really, that was just a test to filter out the visual astronomers. I'm sure they've all rage-closed the page now, but just in case: This guide is for astrophotographers only. None of this will work for visual astronomy because human eyes are weak and uninteresting. Once you have upgraded to cybernetic oculars, then you can revisit this guide for use in visual astronomy.
STEP 1: Focus to the infinity marker left by the manufacturer.
Yeah, that one, the one I said didn't work earlier. Whatever, it's a starting line, not the finish, gosh! *breathes* We just want to get close to focused for now. Moving on.
STEP 2: Point your camera at a bright star
Don't use a planet for this one. That just complicates things. Something like Vega, or Spica, or even Alcyone will work nicely. If you don't know where any of those are, that's okay too. Just nod and point your camera at a big, bright one to the North before anyone notices.
STEP 3: Zoom in on the Live View
Can you see what you're doing? Adjust the Live View settings to digitally zoom as close as you can get. Adjust the focus ring very slightly so that the star is at its smallest point, that's when you're in focus. Nope, you had it, go back. Oh too far! Go back the other way. There it- no, you missed it again...
Get serious! Use a TOOL, you mammals
Our weak, human eyes just kind of fail in the dark. Focusing this way is really hard and can take up a good chunk of your night fine tuning the focus ring (and you probably still won't have perfect focus). Luckily there's an easy to use TOOL for this job! Bring out the Bahtinov Mask to get precision focus!
Bahtinov masks diffract the incoming starlight to create a clear focal point. As you adjust focus, the spikes will move into position. With a little practice, it will cut your focusing time down to mere seconds, and give you photo evidence to be sure.
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Using a bahtinov mask to focus is much easier than trying to focus on the stars by eyesight alone. It will cut down your set up time so you can spend more clear nights taking pictures of the stars. Check out our full collection of professional bahtinov masks here, or learn how to print a bahtinov mask template out at home. Be sure to Like and Follow Johannes Scientific on Facebook for more!