Shooting through a low-power eyepiece on a 150mm refractor, the Sun’s full disk was recorded on 2010 June 12th, around 15:30 AEST. There was quite a bit of heat shimmer at the time, but 2 small sunspot groups have been recorded; they can be seen towards the right side of the disk, positioned about 2- and 4 o’clock. Here’s the lower group:

Sunspots are cooler areas on the Sun, associated with magnetic field effects. Typically, they are around 1,500 degrees C cooler than the rest of the surface, which is around 6,000 degrees C. Sunspots have been notably absent for much of the past 2 years, and are only recently starting to make an appearance again, as the Sun heads towards solar maximum, and greater numbers of spots. Each spot or group of spots typically lasts for a few days, but large ones can be visible for more than a full rotation of the Sun.

The gradual darkening of the Sun’s disk towards the edge (limb darkening) can be seen quite clearly; this is caused by the Sun’s light having to pass through thicker layers of the Sun’s outer atmosphere, compared to the light coming from the centre of the disk.

The Sun is our nearest star, at around 150 million km (93 million miles) away from Earth; at this distance, its light takes a little over 8 minutes to reach us. It is an almost perfectly spherical globe around 1.4 million km (865,000 miles) in diameter, and rotates on its axis approximately once every 4 weeks.

For a couple more images (Moon & Saturn), see the blog

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Image Copyright Duncan Waldron © 2010
This image may not be reproduced without permission
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