Venus and Neptune

I love taking pretty astro photos as much as the next person. However, I also enjoy taking shots that may not be as visually appealing but that show an interesting phenomena.

One such opportunity arose as the planets Venus and Neptune had a close conjunction on April 12th. At closest approach, they were only 40 arc minutes (2/3 of a degree) apart. They would have been a little farther apart by the time they rose in Tucson that morning, but still pretty close. Unfortunately, the morning of the 12th was cloud so I had to wait for the clouds to break. This morning (the 13th) was nice and clear when my alarm went off. According to Stellarium, they would be about 1 degree, 32 arc minutes apart when I went out this morning. 

Again, I fired up the trusty Canon 60D with the 75-300mm zoom lens at 300mm. I didn't bother with the Skytracker as I figured I should be able to get the pair with a fairly short exposure. I took quite a few shots, but my favorite ended up being a 2 second exposure at ISO5000 (which showed the mountains faintly in the foreground). I put an arrow to help you find Neptune.

The star immediately above Neptune is HIP111398 and the two brighter stars to the right are sigma Aquarius (top) and 58 Aquarius (bottom) for those trying to get oriented in the sky.

Although they appear close together in the sky, they are far apart. Venus is a mere 78 million miles away and Neptune is 2.85 billion miles away! Light takes about 7 minutes to reach us from Venus but about 4 hours and 12 minutes to arrive from Neptune! Neptune's diameter is about twice that of Venus, but is appears dim since it is so far away and receives much less sunlight than Venus. 

If you have similar equipment to mine, you can go out and try to get your own photograph of a nearby planet and a distant planet in the same shot for the next few days. 

Reprinted with permission from the Half-Astrophysicist Blog.