[3] Venus rising, caught with a DSLR camera using a 28mm lens set at f/3.5. The camera
was set to ISO 400 and the exposure was 14s.
[4] Venus, shot with a DSLR camera using a small aperture, shows diffraction spikes
caused by the blades of the camera's aperture stop.
[5] Crescent Venus captured with a high-frame-rate camera fitted to a
14-inch telescope.It is possible to apply high-frame-rate imaging to Mercury but its poor
placement in the morning sky prior to sunrise or evening sky post sunset
tends to lead to a rather disturbed view of the planet. Advanced systems can
locate Mercury in the day-time sky for a better-quality view but the dangers
of the Sun being nearby should not be ignored.Venus
The next planet, Venus, is as unlike Mercury as it is possible to be. It is almost
as large and massive as the Earth and, far from having no atmosphere, it
has too much. Telescopically all one can see is the top of a layer of cloud.
There was a time, only a few tens of years ago, when Venus was regarded
as a possible abode for life, but later results have shown this cannot be so.
The temperature is 1000 degrees, the atmospheric pressure is crushing
and the atmosphere is carbon dioxide with clouds of deadly sulphuric acid.
Holidays on Venus are emphatically not to be recommended.
While Venus and Earth are perfect twins in terms of size and mass,
why are they so different? It may well be that when they were formed the
Sun was much less luminous than it is now, so that Earth and Venus may
have started to evolve along similar lines. But then over the ages the Sun
became more powerful. Earth was out of the danger zone. Venus, at 67
million miles, was not. The temperature rocketed and the carbonates were
driven out of the rocks, releasing the carbon dioxide we are familiar withsetting until they disappear. Using the techniques described will get you a
shot of Mercury as a dot in either the morning or evening twilight sky. The
presence of the Moon or even another planet nearby can add an additional
level of interest to the composition. Alternatively, if you are using a fixed
tripod to hold your camera, dropping the ISO sensitivity to its lowest value
and closing the lens aperture to say f/11 or f/22 will reduce your camera’s
sensitivity enough to allow longer exposures. These will show Mercury as a
trail in the sky rather than as a dot.
Another useful technique is to try and capture Mercury over the course
of several days, at the same time, using the same lens settings and from
the same location. If you then load each image into a layered graphics
editor so that the horizons all line up, setting each upper layer to lighten
mode will allow the previous position of Mercury to show through.
This can then be used to reveal the apparent motion of Mercury in
the sky.34Astronomer Book