astro-one

Astrophotography: A How-To

Recently a couple of people have asked me to show them how I shoot astrophotography, so I decided that I would write a blog post explaining how I shoot my astrophotos.

Gear

You will need, at a bare minimum, the following gear:

  • DSLR (DSLR is preferred as the larger the sensor, the better the image in this case)
  • Wide-Angle Lens with at least f/2.8 (f/2.8 is the slowest I would recommend, f/1.4 is even better)
  • Tripod (Something nice and sturdy)
  • Shutter Release (Either a wireless or wired trigger will do, you can find wireless one’s on amazon really cheap depending on your camera)

For the camera, a DSLR is the ideal choice. You can use an APS-C sized sensor, but a full-frame sensor is preferred and will yield better results. I personally use an APS-C DSLR (Canon 60D) because that is all I could afford. For lenses, you can get away with an aperture of f/3.5, but stars will be more faint, it is best if you stick with an f/2.8 or wider. It is important that you use a wide-angle lens, this is necessary for being able to take photos without star trails (we’ll get to this in a bit). I would recommend using a 24mm or wider on full-frame, and 17mm or wider on APS-C. I personally use either a Nikkor 17-35mm f/2.8 IF-ED or a Rokinon 8mm f/3.5. Prime lenses will yield better image quality, but zoom lenses will work perfectly fine. For the tripod, you absolutely need something sturdy, something that won’t move around or vibrate if there is a breeze. Shutter release is absolutely necessary as well, as it will prevent you from causing camera shake when depressing the shutter button.

Camera Settings

This is where it gets interesting. For the camera settings, you will have to use the “500 Rule” when determining your shutter speed. Essentially what this means is that you will have to take 500 and divide it by the focal length of your lens. If you are using an APS-C or other crop-sensor camera, you will need to do a bit more math. It is best if you enable Mirror Lockup on your camera, as the mirror slapping up when the shutter is triggered can cause camera shake.

As an example, on a full-frame camera, with a 24mm lens you would do the following calculation: 500/24 = 20.83. We round the number down to 20, and that is your maximum shutter speed to avoid star trails. On an APS-C sensor camera with a 17mm, you would have to do: 500/(17 x 1.6) = 18.38. So we would round that down to 15 seconds (this is because the shutter speed will jump from 15 sec to 20 sec on a DSLR).

Now that you’ve determined the shutter speed, the rest is pretty simple from there. I recommend using an ISO speed of at least 3200, and the aperture most be opened all the way. If you want the photo to turn out better, with more detail and less noise caused by the high ISO, you have to do what is called “expose to the right” (ETTR). When you use the ETTR method, you are maximizing the signal-to-noise ratio, which allow you to have a higher-quality, less noisy image after post-processing. ETTR requires that you set the exposure so that the image is as bright as it can be without it clipping into the whites, this will allow you to recover all of the detail and information in post by reducing the exposure in Photoshop, Lightroom, or any other editing program that allows raw editing.

Editing

When it comes to editing the raw photo, it really comes down to preference after you adjust the settings for ETTR. Here are some screenshots showing how I edited the photo at the top of this post.

Screenshot 2014-05-26 19.41.30

This is what you will see when you first open the image in Lightroom. From there, I will adjust the Color Balance (Temp/Tint), Exposure, Contrast, Highlights, Clarity, and Vibrance. I will also crop the left side of the photo to get rid of the ghosted figure the walked into the frame. Which leaves you with the following.

Screenshot 2014-05-26 19.48.12

I will then make an adjustment to the tone curve (in point mode).

Screenshot 2014-05-26 19.50.03

I will then use the graduated filter and adjustment brush to minimize the light pollution at the bottom of the image, bring out a bit of detail in the trees, and lighten up the top of the image.

Screenshot 2014-05-26 19.52.32

Screenshot 2014-05-26 19.53.01

Screenshot 2014-05-26 19.53.32

I will then enable “Remove Chromatic Aberration” and adjust the purple and green amounts. Then adjust the post-crop vignetting to highlight-priority and change the amount to brighten up the corners.

Screenshot 2014-05-26 19.56.21

Screenshot 2014-05-26 19.56.11

The before and after:

Screenshot 2014-05-26 20.06.36

 

And there you have it, the final image. Once you edit astrophotography a few times it becomes pretty instinctual and will be a relatively quick and painless process.

 

I hope you enjoyed this post, and thank you for reading! Please feel free to leave a comment if you have any questions.

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2 Comments

  1. Hi James;

    Your work is amazing! I took the beginning Video at Washtenaw Community College. I would really like to pay you $20.00/hour for Photoshop tutoring. Let me know.

    Thanks,

    Mary

    • Hey Mary!

      Thank you very much for that! Please feel free to send me an email through the contact form on my site and I will get back with you on that asap.

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