Friday, June 30, 2017

Happy Asteroid Day

Today is the international asteroid day. To celebrate that I'm posting a photo I took on the 15th of February 2013. It shows asteroid 2012DA14 as it passed just 27.700 km from Earth's surface. 2012DA14 is a small near-Earth object – approximately 45 meters in diameter and has an estimated mass of about 130,000 metric tons. This distance is well outside Earth's atmosphere, but it is inside the belt of satellites in geostationary orbit. The flyby of asteroid 2012DA14 is the closest ever predicted Earth approach for an object this large.

In this 5 minute exposure you can see the asteroid as the bright streak going diagonal to all the star trails.

Nikon D3S with a Nikon 300m f/2.8 lens
5 minute exposure @ f/4 and ISO 1600

Path of 2012DA14. Time in UTC.

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Monday, June 26, 2017

Reflected rainbow at sunset

Rainbows are always opposite the Sun and their centres are below the horizon at the the so called antisolar point. Early morning and late afternoon it the best time to see a rainbow because the sun must not be too high. The lower the sun the higher is the rainbow.

In this photo I took in Vansbro, Sweden, taken just before sunset, the rainbow is as high as it gets and with the reflection in the water, acting as the lower half of a circle, it's easy to see that the rainbow was at its highest position. Had the Sun been any higher in the sky, this circle had been more ellipse shaped.

Rainbows are rarer than might be thought, halos are much more common.

Panorama made with a Nikon D800E with a Nikon AF-S 14-24mm f/2.8 lens

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Wednesday, June 21, 2017

Summer solstice

Today is the summer solstice, the longest day of the year here in the northern hemisphere. Also today marks the beginning of the astronomical summer and the Sun is at its highest position in the sky throughout the year.

In this photo I show the difference between the solar height at noon during winter and summer solstice. In winter it barley gets over the treetops at 3.5° above the horizon and 6 months later, the Sun reaches an height of 50° above the horizon.

Solar height difference between winter and summer solstice

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Thursday, June 15, 2017

Nikon Fisheye 8-15mm F3.5-4.5E ED Review

A couple of weeks ago I received my review sample of the new Nikon Fisheye 8-15mm F3.5-4.5E ED. Since I'm a huge fan and user of fisheye lenses, this type lens has been high on my wish list ever since Canon released their Canon EF 8-15mm f/4L lens back in 2010. A friend of mine has been using the Canon lens for years and he is very happy with it.

When taking pictures of the night sky, my two most used lenses is the Nikon 14-24mm f/2.8 and the Sigma 8mm f/3.5 fisheye lens. Since the sky is so big you need a wide lens to cover as much as possible.

In this review, I will compare my Nikon review sample with my Sigma 8mm F3.5 EX DG Circular Fisheye lens and my Nikon 14-24mm f/2.8. I will also test the Nikon 8-15mm on both FX and DX cameras.

Here are the primary features of the new Nikon lens listed by Nikon:
  • Enables shooting at an angle of view of 180° vertical and horizontal (circular fisheye) when zoomed all the way out, and 180° diagonal (full-frame fisheye) when zoomed close to all the way in with shooting in FX format
  • A full-frame fisheye effect with a diagonal angle of view of up to 180° can be achieved in the range that begins at the DX mark* on the lens and ends at the maximum telephoto position with shooting in DX format
  • Realizes very sharp and clear rendering from maximum aperture throughout the zoom range
  • A minimum focus distance of 0.16 m (0.5 ft.) and a maximum reproduction ratio of 0.34x enable sharp and clear rendering, even with shooting at close distances
  • Adoption of three ED glass elements provides effective compensation for lateral chromatic aberration, minimizing color bleed at the edges of the frame
  • Nano Crystal Coat adopted to effectively reduce ghost and flare for sharp, clear images
  • Adopted a dust- and drip-resistant structure with all moving parts of the lens barrel
  • Highly durable fluorine coat that effectively repels dust, water, grease, and dirt applied to the outer surfaces of the two lens elements at either end (front and rear) of the lens
*The mark on the focal length scale that enables diagonal fisheye shooting in DX format is approximate.

Before I begin my review it’s important to note that the lens I’m reviewing is a sample and not a final product, so things can change.

Thursday, June 1, 2017

Astronomy Picture Of the Day at NASA

Today I'm featured as Astronomy Picture of the Day (APOD) at NASA with my 360° panorama showing both sunset and Earth shadow in a remote mountain area of Jämtland, Sweden.

This panorama is made from 120 still photos taken at a height of 200 meters above the ground. The panorama is a 3 x 8 mosaic where each photo consists of 5 exposure bracketed shots to cover the big dynamic range of both the sunset and Earth shadow.

To the right you can see that the Sun has just set and a small sun pillar is visible just above the horizon giving away the Sun's position. To the left above the horizon is the dark blue Earth shadow with its belt of Venus above. In the middle of the sky the the First Quarter Moon is visible above the mountains, separating these two beautiful sky phenomenon.

The big peak to the right is Storsnasen, some 1400 meters above sea level.

Earth shadow and sunset panorama.

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