Crater Gap Star Trails

February 16, 2013

Crater Gap Star Trails finalCrater Gap Star Trails Final image

Another visit to my favourite Star Trails crater Montana Cuervo near Masdache, Lanzarote. Unlike the others taken from the Crater Floor this is taken looking out through the gap in the rim.

My trip here involves regular bicycle rides as well as photography for which I brought with me my custom bicycle used for these tours. Usually for Star Trails I would ride the 10 miles from the local resort to this location with the Tripod strapped to the rack and the camera and padding in a pannier.

For this trip I decided to combine a day ride to the caves to the north of the Island for pictures there and timed it to get direct to the crater just before sunset. After 65 miles and 4000 ft worth of hills climbed I was feeling a little tired and indeed nearly fell asleep while the star trails were being taken.

I used my Interval Timer and set the camera at ISO 200 and bulb and the timer at 1 minute 59 seconds with a 1 second gap between exposures and aperture at f3.5. I set the timer for 1 hour 44 minutes. I was able to use all the exposures in the image as a strong wind directly towards the camera stopped any condensation forming.

This was taken from the floor of the crater Montana Cuervo near Masdache, Lanzarote. It is not as well visited as many places on the Island. It requires an easy 20 minute flat walk on a footpath from the road to the base of the Crater. Round the right hand side there is a great gash in the Crater wall permitting easy access to the crater floor. There are large numbers of rocks scattered across the Crater floor.

The images were stacked in Startrails.exe

There are 2 methods of taking Star Trail images, either one long exposure of 20 minutes plus or a lot of shorter exposures later blended together. The problem with the first is if something goes wrong such as a walker with a flashlight or condensation you can lose the whole thing so I went for the second. 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. Noise is also helped a lot by taking Dark Frames at the same time as the images. For this I took 2 two minute exposures immediately after the Star Trails with the lens cap on. This enables software to blend these and automatically subtract the standard sensor noise for that exposure at that temperature.

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 light pollution is from a nearby small town. This is minor compared with the light from the resorts to the south luckily hidden behind me

The images used were taken over 1 hour 44 minutes with 52 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, 8mm.

- 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.

- Tripod.

- Interval timer

See this post for a review of this Timer

http://edwinjonesphotography.com/blog/2012/5/timer-interval-remote-review

Tips

- Arrive early, bring a compass or Smartphone, to help find the north star.
- Setup gear while it’s still light, get your composition and wait.
- Shoot test shots, make sure you can see the first stars.
- Wait for that perfect moment and then start the exposure.
- Bring a torch, so you can find you way and make adjustments after dark.
- Bring warm clothing and a snack and drink.

Photoshop

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 Clarity preset

The Star Trails were brightened with adjustments in levels, contrast and brightness.

The light pollution was brought down with saturation adjustments on the red and yellow channels.

For the foreground this was a standard 3 shot HDR taken with light still in the sky.

Some enhancement was done in Topaz, HDR presets, Dynamic pop preset.

Vibrance was increased by 25 points.

Saturation blues was decreased for a more natural grey look in the gravel part of the foreground rather than a blue look which came out in earlier processing.

Brightness was decreased ready for a more natural blend with the stars later.

Noise reduction and sharpen.

On the Star Trails image I selected the sky using the quick selection tool. Then I copied the selection and pasted it in to the foreground HDR image. I used the move tool to line it up with the foreground.  Some pixel level cloning was done along the line of the join to remove some bright areas which came across from the foreground image

BEFORE AND AFTER

Below are the Before and After images. First the HDR image of the foreground after all processing. Then one of the single star trails exposures, then the Star Trails Image after merging of the exposed frames but before other processing and then the final result.

Tonemapped Foreground

Crater Gap Star Trails ForegroundCrater Gap Star Trails Foreground

A single exposure which went towards the final Star Trails image

Crater Gap Star Trails  single exposureCrater Gap Star Trails single exposure

Merged Star Trails image

Crater Gap Star Trails  all star exposuresCrater Gap Star Trails all star exposures

Final Image

Crater Gap Star Trails final imageCrater Gap Star Trails Final image

For licences see Crater Gap Star Trails

Edwin Jones

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