Transit of Mercury

transit of mercuryI set up the telescope in the last patch of afternoon sunlight on our back lawn and catch an image of Mercury mid-way through its transit across the Sun. This is the first time that I’ve seen Mercury: as we’re in a valley, we’re never well placed to see its brief appearances at dawn and dusk.

transit telescope

I don’t have a solar filter for the telescope so I project an image onto a sketchbook page, then photographed the image. I feel that it’s safer to project anyway: a friend accidentally burnt out the lens of his smart phone when he moved his telescope into position, having briefly removed his solar filter to make it easier to level up the shadow. That’s £70 for a replacement lens but you can’t replace an eye as easily.


Detail from the projected image of the solar disc. Sunspots appear in pairs, magnetically charged as north and south: imagine a horseshoe magnet connecting them beneath the photosphere.

Squeezing my camera in between telescope and sketchbook to take the photograph resulted in an oblique view of the solar disc so I skewed and stretched the image in Photoshop to fit into a yellow circle (top image).

planetsIf we could see the Earth’s silhouette alongside that of Mercury, it wouldn’t be much bigger than the larger sunspot (left).

Seeing the progress of Mercury across the solar disc gives an impression of the scale of the Solar System; 99.8% of the mass of the Solar System is contained in the Sun.

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