Tag Archives: stars

Astrophotography combined with foreground light painting

In my youth I was very interested in astronomy. However, the interest faded, or should I say it went into a sleeping mode for a long time. Today, new digital cameras with full-frame sensors has made it feasible to get better photos of the skies. In line with this, I decided to give my new camera Sony a7r and ultra-wide angle lens Samyang 14 mm f/2.8 a try for astrophotography. On Friday night I went to a location called Birkelands-vatnet (Birkeland lake) not far from my home in Vest-Agder, Norway. The location is not ideal for astrophotography since it is too close to the city lights of Kristiansand (15 km). But for a test it would do. It was the first clear night for a long time, after weeks of rain and clouded sky. The moon was almost new, which was also a necessary condition. I parked the car and set up the camera with a remote cable release (intervalometer). The night was very dark and I was totally dependent on the flashlight. The view at the lake was against the city, which was not perfect since the city lights would probably dim the stars.

Viewfinder problems

I tried to look through the electronic viewfinder of the camera, but nothing was visible there apart from lots of noise. Apparently, the a7r viewfinder is useless in very low light. The live view monitor was no better. So if astrophotography is your main goal, then a camera with an optical viewfinder is to prefer at present. Left without the possibility to adjust focus and perspective I had to use the distance scale on the lens to set for infinity. The infinity mark on the Samyang 14 mm is not well defined so I had to take a chance. Luckily, 14 mm’s are not very picky on exact focus.

Birkelandsvatn background photo

Birkelandsvatn background photo, View a larger version of this photo on Gallery – Astrophotography.

Birkelandsvatn foreground photo

Birkelandsvatn foreground photo

Birkelandsvatnet composite image

Birkelandsvatnet composite image

I had read posts about astrophotography at the Internet and knew what would be the best settings for the camera. ISO was set at 3200, aperture at 2.8, shutter at bulb (25 secs on the intervalometer) since the lens was at 14 mm focal length. First, I made the background exposure. The stars look like points in normal view, but with magnification it is possible to see streaking. Then I focused for the foreground and made a second exposure set for identical shutter time, but now at ISO 800 and f/8. I used the flashlight to illuminate the foreground while exposing so that the grass would be correctly exposed. This can be called light painting and by moving the flashlight it gives a softer look to the image. I had mounted a diffuser made from white translucent plastic foil (carry bag) in front of the LED diode in the flashlight to get more diffused light.

Making a composite image

Back home, I wanted to make a composite image of the background skies and the foreground lake bank covered with grass. This can be done in Photoshop Elements version 9, which is the version I have. First, I adjusted the two exposures in Lightroom to get proper white balance (auto was fine here) and reduction of noise in the sky (Details, sharpness, luminance). I also had to reduce the foreground exposure a little. Then I opened the photos in Elements and made the sky image background. I also opened the foreground image. Then I dragged this image on top of the background image. The alignment seemed to be done automatically. Elements 9 can work with layer masks, so I opened a layer mask along with the background. Using the gradient tool, I was able to make a horizontal gradient so that the background image was visible in the upper part of the image and showed the sky. The foreground image was visible in the lower part of the composite image. The gradient tool was perfect here since the dark banks at the other side of the lake disguised any possible stitching between the images. The final result was not so bad considering this was my first attempt with this technique. The light beam from the flashlight is visible in parts of the image, so be careful not to turn the flashlight against the camera. I have learned a lot from internet pages, and I would in particular recommend Adam Woodworth’s excellent article (Introduction to landscape astrophotography) and beautiful photos which can be found at the Luminous Landscapes webpage (www.luminous-landscape.com).