Tuesday, May 6, 2014

How to photograph stars and constellations

This article will focus on tips and techniques to photograph stars and constellations using a regular camera and tripod. No telescope is required and even a simple camera will be sufficient.

The first difficulty that a photographer encounters is familiarizing himself with the night skies. It is better to begin with photographing well known constellations such as the big dipper, Orion and also to use free software such as "Stellarium" or "Google sky map" to become more familiar with the skies.

Photographing constellations is not a hard task. A telescope is not required and even a long zoom is not required since the constellations are wide. However a tripod is a must to perform long exposures. Here are some tips and techniques for constellations photography:
  • A tripod is a must have. If you are using a small camera even a small tripod will do, but you can't photograph stars without it
  • Photograph from the darkest place that is available to you. Many cities suffer from light pollution which will make the constellation background bright or even white
  • Usually you will not see the entire constellations with your eyes or on the small LCD screen of the camera but just the brightest stars. Use a wide focal length (no zoom) to include everything in the photo and crop later if necessary. Also you can take some test shots until you create the proper composition. For the test shot raise the ISO to 3200/6400. You don't care about noise and it will save lots of time.
  • Perform many tests and check the photos on a computer or laptop screen. It is impossible to see the photos properly on the camera LCD screen.
  • If possible, add some terrestrial landscape to the photo. Trees, mountains and building will give an extra touch to the photo. However take into account that light pollution is more severe in the lower part of the sky, so you will need to compromise.
  • The earth is rotating around its axis and in a long exposure the stars will create trails. Use bigger aperture (Lower F number) and raise the ISO definition to decrease the exposure time. If you like star trails, go ahead and photograph them. Too high ISO value will create more noise in the photo so don't raise it too much, usually 400 is a good value.
  • As a rule of thumb divide 500 by the focal length of the lens to estimate the longer possible exposure before the stars will make small trails.
  • Use manual focus and focus on a bright star that you see, even in a different constellation and even in a larger focal length (zoom). If you can't find a star use infinity.
  • Some people like to add tiny thin lines to the final photos. These lines will emphasize the constellations familiar shape. I do not like to add these lines as you will see in the examples below, but it is a matter of personal taste.
  • To prevent shakes from the cameras either use a remote control or shutter release. If you do not have these tools, just add a short delay 2-10 seconds to the photo. This feature is available on all cameras and is mostly used for selfies.
  • Use the Noise-Reduction feature in your camera. Usually it is turned on by default for long exposure. Using NR will take longer so there are times you can take a single dark photo (long exposure with the lens cap on) and do the NR in software later, but for most amateur it will be best to do it upfront immediately and automatically.
Another problem is uploading the photos to the Internet, since many sites compress them during the upload process. These kind of photos, with lots of black areas and just few white dots, are not compressed very well. If you have your own website, you can upload the photos to there, otherwise a service like imgur can provide a reasonable solution. Also PNG format will give better results from the JPEG format for sites like Facebook.

And now for several examples, all taken with an old  Sony Alpha 100 DSLR with 28-105mm lens, usually at the wide side. You will need to click the photos to see a larger image.

The first photo is the well known constellation - Canis Major - the great dog. Notice the difference between the black at the top of the photo and the brown at the bottom, due to the light pollution. Also a high ISO value was used and the photo has a lot of noise.

Canis Major - Great Dog
Canis Major - Great Dog
Perseus constellation
Perseus constellation
Here is the famous group Orion, Usually known for the trapezoid but includes many more stars above and to the right.
The entire Orion constellation
The entire Orion constellation
Sometime it is better to focus on part of the constellation. The following example shows the Pleiades (M45) and the Hyades in Taurus (The Bull). The brightest star is Aldebaran.
Pleiades (M45) and the Hyades in Taurus (The Bull)
Pleiades (M45) and the Hyades in Taurus (The Bull)

For a more advanced photographer, the skies are the limit (just as usual). Here are some more ideas which require time and investment just to give you a taste of the possibilities.
  • A tracking device will enable longer exposure without smudging the stars. A very affordable tracking device is the iOptron SkyTracker.You simply aim it at the north star and connect the camera to it. Such a device will enable long exposure as long as your camera supports.
  • There are special blocking filters which can somewhat improve light pollution, but do not expect miracles, go to a darker place.
  • Larger zoom lens can be used to photograph smaller objects. Such objects will be detailed in a separate article but as a taste here are the Pleiades taken with a simple Canon SX50 camera in just 1 sec of exposure. The mini dipper shape (which can be seen with the naked eye) is visible with dozens of additional stars.
הפלאידות - צביר בקבוצת שור, מכונה גם M45
M45 - Pleiades

1 comment:

  1. However a tripod is a must to perform long exposures. Here are some tips and techniques for constellations photography:sober house