Step by step

STEP 1

Decide how to image the event. A wide-field setup allows you to grab the entire lunar crescent with a small Venus. A scope with a focal length around 1,000mm is ideal. A lower focal length works too but the Venusian crescent may become lost, while a longer focal length shows the crescent but is trickier to work with.

STEP 2

As described in the main text, attempt to centre on Venus as early as conditions allow. A driven, correctly aligned equatorial mount is highly recommended to keep the planet in view without the need for manual adjustment. Do checks to make sure Venus is in the field of view to avoid a last-minute panic if the drive stops working.

STEP 3

Once Venus is in view, focus on it as accurately as you can. If you do this well before the occultation, make sure you re-check the focus as the heat of the day can cause it to drift out. If you’re planning to use a high-frame-rate planetary camera consider using an infrared pass filter. This will darken a blue sky and improve

STEP 4

If you plan to image using a DSLR, the bright scene means a low ISO can be used. This will improve tonal quality and keep noise down. Stopping the lens aperture down will increase your depth of focus allowing you a degree of error on your focus setting. Higher f-numbers may reveal dust spots on your camera’s sensor though.

STEP 5

A short exposure will work best. Take a test shot and examine the histogram. Ideally, the main data peak should lie between the two graph ends. Venus appears bright and virtually white which makes getting an ideal histogram tricky. Just ensure the lunar crescent doesn’t over-expose to pure white.

STEP 6

If you’re using a high-frame-rate planetary camera, ensure you’re set for a high frame rate and image the planet in short bursts of less than 4 seconds during the main occultation phase. This will allow you to maintain a sharp planet during the registration-stacking processing as it gets covered by the edge of the Moon.