Tuesday, October 20, 2015

Triple Conjunction

October 20 - I dragged myself out of bed before 6:00 this morning to have a look at the triple conjunction ... yeah, that's pretty early for me. Weather forecast has the rest of the week cloudy including when the conjunction is probably at its best on Thursday or Friday.

I got this image while the sky was still pretty dark at 06:44. I zoomed in on the three planets and placed the backyard tree-tops in the frame for reference. By stopping down the lens by 1/3 stop, I removed the wonky looking diffraction effects that were especially noticeable on Venus and obtained the more pleasant diffraction spikes from the iris shown here.

Double checking in my SkyTools atlas, I confirmed that at the top of the frame is the brightest object, quarter phase Venus, shining at magnitude -4.4. The next brightest object, lower in the sky, is Jupiter shining at magnitude -1.8 with moons Ganymede above and Europa below. Further down and to the left is the much fainter Mars shining at only magnitude +1.7.  The rest of the stars are from an unexceptional part of Leo, the brightest of which is Chi Leo just to the left of Jupiter at magnitude +4.6.

Canon 7DII, EF 100-400mm f/4.5-5.6L II -  100mm, f/5, 2s, ISO-3200

As dawn was breaking, Danielle called me back outside to show me that Mercury was now also visible. This second image was taken at 07:15 with a wider field of view and a much shorter exposure. It shows the same conjunction pattern at the top of the frame now joined by Mercury just rising before the sun. At magnitude -0.8, it is actually almost 10 times brighter than Mars. I had to brighten all four planets in post-processing as they were nearly completely washed out by the brightening sky.

Canon 7DII, EFS 18-55mm -  35mm, f/5, 1/40s, ISO-800

October 27 - After a weekend of torrential rain, a bit of a break in the clouds this morning allowed me to get another shot of the conjunction. In seven days, the planets had moved into a different configuration as shown in this 06:00 image. The full moon was to my back, illuminating both the clouds and the foliage.

In the picture, Jupiter is now the upper most planet shining at magnitude -1.4.  It has moved further east (down towards the eastern horizon) in the sky. This is normal "prograde" motion of the planet against the background of stars due to the planet's proper orbital motion. Note that Chi-Leo, the brightest star above and slightly to the left of Jupiter, marks where the planet was last week. By coincidence, Ganymede is once again above and Europa below Jupiter, both having made one full orbit of the planet in a week's time. Venus, at magnitude -4.3, is now further east than Jupiter, having moved considerably further in the sky than Jupiter. Near the center of the frame, Mars, shining red at magnitude +1.9 has also moved further east. For reference, the brightest star up and slightly to the left of Mars is magnitude +4.0 Sigma-Leo.

Canon 7DII, EF 100-400mm f/4.5-5.6L II -  100mm, f/5, 2s, ISO-1600

Five minutes later, the clouds rolled back in again. As they did so, the effect looked like van Gogh's Starry Night.

October 29 - Two more days have not resulted a significant change in configuration. This 05:20 image again shows that Venus is progressing most quickly through the sky, having almost caught up with the position that Mars held two days ago. Jupiter itself has not moved noticeably but the moons have progressed in their orbits. Europa is now uppermost with Io just below. Callisto is visible below but Ganymede is now too close to the planet's glare to be seen in this image.

Canon 7DII, EF 100-400mm f/4.5-5.6L II -  100mm, f/5, 2s, ISO-1600

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