Step by step

STEP 1

Select the type of camera; a DSLR or other type of stills camera can deliver a decent result, but an accurate timing can be tricky. The occultation disappearance on 2 September takes place at low altitude and may be distorted by seeing. A high frame rate device overcomes seeing effects, and has better timing accuracy.

STEP 2

The lon er the effective foc l len th, the n rrower the field of view. DSLRs will also typically offer larger fields than high frame-rate cameras. Decide whether you want to image with all the Moon’s surface in view or to zoom into the region of interest. Wider field setups take the pressure off for the reappearance event.

STEP 3

If you plan on making a timed event recording, it’s essential that the DSLR’s clock, or the onboard clock of a computer being used to control a high frame rate camera, has been synchronised to an internet time server. Time server examples include time.google.com and time.windows.com. A computer’s operating system normally offers synchronisation options via its ‘Date and time’ settings.

STEP 4

Accurate focus is essential for occultation images. Fortunately, for lunar occultations of bright stars, you have two easy focus targets – the star which is being occulted and the Moon’s surface. Take your time over focusing, and revisit the task several times before disappearance as well as reappearance.

STEP 5

Ensure the object being occulted is visible in your images. This can be done prior to disappearance, and a note of the settings should be made to ensure the same values are used for reappearance. Exposures should be kept less than 0.5s in length, and balanced with as low a gain (ISO) as possible to reduce noise.

STEP 6

Individual frames can be extracted from an AVI movie sequence using freeware such as VirtualDub (virtualdub.org), or PIPP (bit.ly/3x2vCJ3). In VirtualDub it’s possible to step through the sequence, frame-by-frame, copying frames to the clipboard (Ctrl-1) to load in an image editor.