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How to focus a DSLR camera lens on the stars

Updated: Jun 6, 2023

Astrophotography can be done without a telescope or an expensive mount. Almost every beginner astrophotographer starts out by imaging the night sky with a DSLR camera and a wide-field lens.


But if you're trying to get a magnificent picture of the Milky Way or the Orion constellation, getting the perfect focus on your lens is crucial. Focusing a camera lens during the day is completely different than focusing at night. In this tutorial, we will show you how quick and easy it is to achieve the perfect focus with any DSLR camera or lens.


For this tutorial, we will be using our Canon 7D Mark II and a 24mm lens. Make sure to watch the video at the bottom of this post if you'd like to see this in action!


Tutorial on how to focus a telescope and a DSLR camera in just a few seconds using a cheap Bahtinov mask


Step 1 - Check Your Settings


Before even looking up to the stars, we need to make sure the settings on your camera are correct and will make the task easier. Here is what we recommend:


  • Mode: The Mode does not matter much since we're only going to be focusing. We suggest being in Manual or Bulb mode since you will likely be imaging after that but, as you can see in our image below, we were in AV mode that night and it did not make a difference. Just make sure you switch to Manual/Bulb mode when you are ready to image.

  • Aperture: Have this wide open, so the lowest possible number your lens will allow. In our case, it will be f/2.8. This will help your sensor gather more light and so you will have not problem seeing the stars. Note that after achieving focus, we usually bump that number up to f/4 in order to make sure we have pinpoint stars on the edges of our images. Refer to our Barnard's Loop episode for more info on that and a comparison of Astrophotography at different apertures.

  • ISO: The ISO doesn't matter too much, although it might help if you set it higher than the default number. We usually do 800 or 1600 by habit, and sometimes lower it down when we are ready to image.


How to focus a DSLR camera at night, tutorial

 

Step 2 - Ensure Your Lens is Set to Manual Focus


Before actually going outside and pointing your camera up, ensure that the lens you are using is set to Manual. Do not expect to be able to focus on the star by simply using Automatic focus, that won't work, and if it does, that's just luck.