Halnaker Downland Star Trails
Last Saturday night 13th December was very clear very cold and very still. It was also the peak of the Geminid Meteor Shower. I saw at least 10 during the time I was out but only one was bright enough to show up with the exposure length used. The image was taken near Halnaker north of Chichester looking towards the South Downs. The sky glow visible is from London 60 miles to the north.
The image was taken with a Sony A700 and a Samyang Fisheye Lens using a Tripod.
I used my Interval Timer and set the camera at ISO 200 and bulb and the timer at 2 minutes at f3.5. I set the timer for 1 hour 38 minutes but did not use the first 18 minutes as it was still a bit too light so the star trails shown are for 1hour 20 minutes. I had some extra kit for Star Trails this time. First a Head Torch which was very useful for taking things down in the dark. The second bit of kit was even more useful. This was LensMuff which is a holder for chemical hand warmers which secures round the lens with Velcro. The night was perfect for a heavy dew and frost and by the time the sequence finished at 18.45 my tripod was thick with frost but the lens stayed clear of any dew or frost.
The images were stacked in Startrails.exe. It would normally be very time consuming to blend all the pictures together but there is now free software available to do it for you at http://www.startrails.de/html/software.html
With the method of stacking together shorter exposures noise is not such an issue so I turned off the Cameras noise reduction settings. If these are turned on it doubles the exposure length as a second image is taken automatically of the same length for the noise reduction process. This also causes gaps in the Star Trails if multiple images are blended. Noise was corrected later with software.
The circular pattern is formed by pointing the camera towards Polaris the Pole Star near the Plough. As the Earth turns stars more above the pole do not appear to move as much as those more above lower latitudes. I had with me an HTC Android Smart Phone with the Google Sky App. This enabled me to locate the pole star while there was still light. The foreground comprises an image taken while there was still light. With the Camera and Tripod locked in position the star trail images were taken later when the stars were out.
The Sky Glow is from London 60 miles to the north. Also I kept frames with some remains of blue in the sky which avoids any orange glow from light pollution..
The images used were taken over 1 hour 20 minutes with 40 images of 1 minutes 59 seconds exposures each with 1 second gap between each exposure on the timer. These were stacked with the startrails software.
All the settings and equipment were as follows
- Sony A700 Camera.
- ISO 200, f3.5, 1 minute 59 seconds.
- Long Exposure and high ISO noise reduction set to off. Otherwise the Camera would take One minute and 59 seconds between each shot for its own noise reduction resulting in great gaps in the Star Trails.
- Samyang Fisheye lens 8mm.
- Interval timer
- LensMuff holder for chemical hand warmers wrapped around the lens to prevent condensation.
See this post for a review of this Timer
- Arrive early, bring a compass or Smartphone, to help find the north star.
For the Star Trails the stacking software works on jpegs which are then saved as a Tiff.
After opening in Photoshop some extra detail was brought in with Topaz Adjust and Noise reduced with Topaz DeNoise.
The Star Trails were brightened using Astronomy Tools Action to select the brighter stars and contrast and brightness adjustment..
After flattening the image duplicate layers were brought up to sharpen.
For the foreground this was a standard with light still in the sky.
On the foreground image I selected the foreground using the quick selection tool. Then I copied the selection and pasted it in to the star trails image. I used the move tool to line it up with the silhouetted foreground.
BEFORE AND AFTER
Below are the Before and After images. First one image of the stars, then the Star Trails Image after merging of the frames but before other processing and then the final result.
Single image including the meteor
Merged Star Trails image
Keywords: astrophotography, branches, celestial, Chichester, dark, Downs, dslr, England, exposure, fisheye, fisheye lens, Halnaker, landscape, lens, long exposure, nature, night, night sky, north star, photography, Photoshop, pic, samyang, sky, sonyA700, South Downs, stacking, star, star trails, stars, Sussex, the plough, Topaz, tree, UK, West Sussex, wide angle, winter
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