Planetary Alignments during the Spring of 2004


Not quite a rerun of the 2002 events, but similar in many ways. All 5 naked eye planets put in an appearance, though they are not as close together as last time. Only Mercury is missing from my record - although I saw it visually in mid March Inever got the opportunity to catch it in the telescope or photograph it in a pleasing setting.


9 Apr 2004: A quick tour of the Solar System

Four planets and three moons, 9 Apr 2004

During April and May 2004 four of the five naked eye planets are gathered together for convenient viewing as soon as it gets dark in the evening. On the 9th April I attached my Philips ToUCam Pro webcam to my 8-inch telescope to take a tour of them.

With the exception of Mars, which received attention last autumn, this was the first time I have used the webcam on the other planets, and I am amazed at the quality of Jupiter and Saturn, and pleased that their moons have come out so well too. All planets are presented at their actual sizes as seen by the webcam (0.3 arc seconds per pixel), though of course their different distances (quoted below for 9th April 2004) hides their true sizes. North is up and East is left, so the sun shines from the right.

Moving outwards from the Sun...

  • Venus is 12,104 km in diameter (almost the same as the Earth) and is also the closest at 95 million km.
  • Mars is 6,794 km in diameter (half the size of Venus) but lies at 300 million km, so appears tiny by comparison.
  • Jupiter is the largest planet, with a polar diameter of 134,200 km (11 times that of the Earth), and lies at 693 million km. Its fast rotation period of only 10 hours gives it a noticeable equatorial bulge, and also visible in this shot is the Great Red Spot, a storm that has been raging for over 300 years. Two of its moons are visible, Io and Europa, both of which are similar in size to our own. With the fast rotation period, turbulent weather systems and 4 bright moons whirling around the planet there is always something to see, as this animation from 16 May 2004 shows.
  • Saturn is the second largest planet with a polar diameter of 108,000 km, but lies at 1,377 million km, nearly twice the distance of Jupiter. However,its magnificent ring system makes up for the smaller size of the planet. The moon Titan is 48% larger than our own.

Of course the planets are not really this close together in the sky - see the picture below on 24th April for where they really were.


24 Apr 2004: The Moon amongst Venus, Mars and Saturn

Saturn, Moon, Mars and Venus

On this evening the crescent Moon (heavily over-exposed in the picture) passes through the group.

Jupiter is high in the south so is not possible to include in the same shot. Note also how faint Mars is now that it is so much further away than when it came to a vey close opposition last year.


21 May 2004: The Moon amongst Venus, Mars and Saturn (again!)

Saturn, Mars, Moon and Venus; 21 May 2004

A month has elapsed and with the Sun having moved 30 degrees through the sky since last time the planets are much lower down by nightfall. Indeed it was a struggle to find a spot with a clear enough view to the horizon to catch Venus once it was dark enough for Mars and Saturn to show themselves. As it is, they are only just framed in the gap to the right of the tree.

The Moon is just under two and a half days old, so is a much narrower crescent than during the same encounter last month. The crescent is still over-exposed, but next to it the dark side of the Moon, lit by Earthshine, is easily visible.

Saturn's position in the sky relative to the stars has hardly changed, so you can see that Mars has caught up with it, and will shortly overtake it. By contrast, Venus, on an orbit inside that of the Earth, is drawing rapidly in towards the Sun and will pass directly in front of it on 8 June 2004 - the first time this has happened since 1882.

8 hours earlier the Moon passed directly in front of Venus. Venus too is a crescent as it is currently showing its dark side towards us, so was a fine opportunity to compare the relative size of the two objects.

The event would be a challenge see, taking place around mid-day, but unfortunately it proved too cloudy, so the first opportunity to catch them was not until this evening. The Moon was now too far from Venus (4 degrees) to be seen in the same field of view in the telescope. However, photos taken of them separately reveal the difference in size, as Venus, though 4 times larger than the Moon, is over 120 times further away.

Venus is very over-exposed as it is inherently much brighter than the Moon, being nearer the Sun and covered with dense white clouds. Despite this, something is clearly odd about the shape, and the view is similar to how it appears in binoculars or a hand held telescope. For a close-up view, revealing its true shape, see here.

2 crescents - Moon and Venus


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