ASTROPHOTOGRAPHY CAPTURE

Take the perfect astrophoto with our step-by-step guide 

- Pete Lawrence

Lunar occultations of planets

How to image a far-from-easy Uranus disappearing behind the Moon on 14 September

Occultations of the planets by the Moon aren't very common and when they happen, all fingers are crossed for clear skies. If the weather holds good for the lunar occultation of Uranus on 14 September, there will be a lot of interest in the little planet, certainly more than it normally gets.

Unlike the main planets closer to the Sun, Uranus appears dim, right on the threshold of naked-eye visibility. It's also rather distant and looks small even through a sizable telescope. This presents issues with visually observing the event as well as some awkward problems when trying to image it.

These will be exacerbated by the fact that the start of the occultation will involve the Moon's bright limb passing in front of the planet. Setting up captures for Uranus will certainly overexpose the Moon, while exposing for the lunar surface may mean Uranus is lost from the shot altogether.

Fix upon framing

There are various imaging setups that can be used for this. First consider how you want to record the view: a wide field to cover the whole Moon or a riskier narrow field zoomed in on the planet? The latter isn't that hard to organise for the disappearance event, but adds uncertainty in when Uranus reappears from behind the Moon's dark limb: here you'll need your best guess as to where the planet will reappear.