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Astrophotography with a DSLR or Mirrorless cameras.

Taking a landscape photo at night, with the stars in the background, is essentially taking a night landscape. These night landscapes or nightscapes, that include stars as a feature, are another form of astrophotography.

The following are some points on Nightscape Photography with a consumer camera.

Camera Selection:

Unlike Deep Sky Astrophotography, where you are worried about over-sampling or under-sampling by trying to match a pixel size to the focal length of the telescope, (with about an arcsecond of sky per pixel), nightscape images focus on capturing the light in one or just a few images on a tripod.

In general for nightscape, the cameras with sensors that have the biggest pixel size and the lowest noise at high sensor gain, i.e. highest ISO settings, are the best for Astrophotography.

The pixel size is usually a measure of the light collection capacity of each pixel in the sensor. If you equate the pixel of a sensor to a bucket that collects light photons, then it would be the size of the bucket. The bigger the bucket, the more it collects before overflowing. In other words, a bigger pixel usually means a larger dynamic range for the sensor. A large dynamic range reduces the chance of the brighter stars being overexposed when trying to capture the less bright parts of the sky.

Camera points to note:

  • Use a camera that has a manually mode. (ie. set ISO, aperture and exposure)
  • Ensure the camera can save images as RAW files. (and set it to the largest RAW mode)
  • Select a camera with a large sensor. The larger the sensor, the wider the field of view.
  • Select a camera with the largest individual pixel size. This also usually means a low ‘megapixel’ count.
  • Look at cameras with lower background noise at high ISO values. It often means a later model camera with improved sensor technology and newer controller chips.
  • A camera that has a live view mode, that has a digital zoom control for the live view, is best to simplify manual focusing.
  • A camera with an LCD that can be angled up when the camera is low on the ground is very useful.

The Lens Selection:

Note the aperture of the lens. The F-number of the lens is important.

Note also that some (lower cost) zoom lens have a variable aperture depending on the zoomed focal length. Ensure you have your desired aperture for the focal length you intend to use.

Each stop reduction in aperture has half the light-gathering area of the previous stop (or F-number).
The lower the F stop number, the better the lens will be for night photography.

F-Stop comparison
Figure 1 - F-Stop comparison

Lens points to note:

  • Use a lens with the lowest F-stop or largest aperture. This will maximise the light gathering of a night sky on the sensor.
  • Use a lens that has manual focused (and put it on manual)
  • If the lens has image stabilisation, turn it off.
  • Consider using a thin strip of tape to secure the focus once you have the lens focused (such as painters masking tape)

Tripod:

  • Use a solid tripod.
  • A tripod that can be adjusted very low to the ground is useful for getting those shots of the milky way as a background with an interesting foreground subject.
  • A solid ball head that can easily carry the weight of the heavier camera and lens has larger knobs for adjusting on cold nights with gloves and that doesn't move for those long exposures.
  • A tripod that has a quick release, such as an Arca-Swiss for the camera is useful. Even better is an Arca-Swiss 'L' bracket to enable a quick change from landscape to portrait orientation.

Extras:

  • An external intervalometer, (cabled or wireless), or use a timer to reduce camera shake.
  • Lots of Batteries as the night cold reduces battery performance.
  • Large Memory card (and spares).

Notes on taking Nightscape Photos:

  • Use a solid tripod with a strong ball head to reduce camera movement.
  • Set the tripod firmly on the ground to minimise movement. (consider weighing it down with a sandbag or similar if necessary)
  • Set photo mode to RAW to maximise data stored.
  • Set white balance to 3000k
    • (Note: when using RAW mode, setting the white balance is just an EXIF setting in the saved file . This will be used as a starting colour balance setting in Lightroom for later photo processing)
  • If you are possibly thinking of stacking photos, then also consider taking some dark frames at the same time (and temperature) and using the same exposure length as the original images. (ie. images with the lens cap on).
  • Noise reduction - consider turning internal noise reduction off, particularly for star trails & photo stacking. In-camera noise reduction can take too much time. Dark frames or stacked photos using Sequator can also be used to reduce noise in the final image.
  • Focus:
    1. Ensure you are set to Manual Focus.
    2. Temporarily set to a very high ISO.
    3. Initially set the lens focus to ‘infinity’.
    4. Turn on ‘live view’ & find a bright star.
    5. Set maximum screen zoom. (eg. x10)
    6. Focus on a star.
    7. Once focused, consider placing a thin piece of tape on the focus ring to prevent it moving.
  • Exposure setting:
    • The 500 Rule is a simple guide to find the maximum exposure needed before stars are blurred by the rotation of the earth.
      (other exposure guides such as the '600 Rule' & NPF also exist).
      Max seconds exposure using 500 Rule = 500 / (focal length x crop factor).
      The crop factor an APS size sensor is about 1.5
      Example: Canon 6D Mk2 & 17mm lens.
      The exposure is 500/(17x1) or about 30 seconds (the Canon 6D is a full-frame camera so the crop factor = 1)
    • Take test shots
      1. First try 15 seconds at a high ISO of about 3200 or more and adjust the framing of the photo.
      2. Next set exposure to the max for the focal length used (in this case, 30s)
      3. Try various ISO settings and while aiming for the lower ISO with a longer exposure without stars blurring.
      4. Zoom into the test photos & check the centre as well as the edges of the photo for correct focus and that the stars are round. If blurred from movement, reduce exposure time, up the ISO and try again.

Visualise what is in the sky

Use a planetarium and planning applications to visualise the location of the Milky Way in the sky for the date and location of your photoshoot.

Planetarium:

Planning:

Framing Nightscape Photos

The normal photography rules still apply:

  • Rule of thirds
  • Leading lines
  • Frame the subject
  • Add a foreground interest item such as people, an old car, trees, a mountain range silhouette, e.t.c.

Editing Nightscape Images

Consider using Adobe Lightroom
Suggested starting settings for an image (in Develop Mode):

  • White balance about 3300k. (so the background is not yellowish but dark blue/black)
  • Highlights slider towards the left so no highlight clipping.
  • Blacks slider to just above clipping.
  • Contrast, Clarity & vibrance sliders to the right about 2/3.
  • Texture about a 1/4 to the right.
  • Sharpening sliders about ¾ to the right.
  • Slight Luminance & Colour noise reduction.
  • Lens profile set to your lens.
  • Remove Chromatic Aberration.


Resources

Richard Tatti

Alan Dyer

PhotoPills Tutorials

Noise Reduction applications

Applications that increase the signal to noise ration (ie. reduce noise) by stacking multiple images.


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