STEP BY STEP
STEP 1
Decide on how you want to present your results. For a strip showing several shots of Algol side-by-side, a larger image scale works best. This can be achieved using a telephoto lens or a camera attached to a telescope. For a before-and-during eclipse comparison pair covering the whole of Perseus (35x30°), a 28mm lens or shorter is ideal.
STEP 2
A tracking mount is recommended for sharp star images but relaxing this requirement allows the use of fixed platforms such as a tripod. Here, the best option is to let the stars trail for, say, five minutes. The star trails can then be compared side-by-side. A fixed platform will need to re-pointed at frequent intervals to keep Algol in view.
STEP 3
Set your equipment up and frame either Perseus or Algol as required. Camera settings will depend on your particular setup but the aim here is not to produce a grossly too over-exposed shot of the star. Start with a value of ISO 400, a camera lens at f/8 (this will be fixed for a telescope of course) and an exposure of, say, 4s.
STEP 4
The shot should ideally contain stars as dim as the faintest comparison star shown here. Adjust your camera settings so that the faintest star marked shows up in the image. For wide shots there are many choices, but for the narrow image make sure that Pi (/) Persei is showing. Note any star patterns on the threshold of visibility in your shot.
STEP 5
Take shots at intervals of say, every 15 or 30 minutes, covering the start or end of an eclipse. Catching a full 9.6 hour cycle is difficult and requires luck with the timing of the eclipse’s start. Check each shot to ensure the threshold stars remain visible. If they disappear, increase camera sensitivity; if too prominent, knock sensitivity back slightly.
STEP 6
When you’re done, download your images onto a computer and, using a layer-based editor, align Algol across the layers. Make a vertically tall but horizontally narrow selection strip centred on Algol, copy the star from each layer and paste into a new image next to one another. The final sequence should show the dip into, or rise from, eclipse.