John Griffiths Astro Pages > GCSE Astronomy

John Griffiths Astro Pages

GCSE Astronomy — Straightforward Astro Photography

GCSE Astronomy > [Revision] > Astro Photography > [Useful Links]

Notes on this technique:

· You need to use a camera where the shutter can be left open. Many compact digital cameras may not have this facility, as many are designed to be automatic. Of course you do not need the flash on, as this is of no use at all. Digital Single Lens Reflex cameras (DSLRs) will provide the best results. All DSLRs (or film SLRs) have a ‘B’ stop that enables the shutter to be left open.

· If background features (trees, buildings etc.) are included they can add a degree of dramatic effect to the image.

· This technique needs relatively dark skies, with as little light pollution as possible. However even in fairly poor skies reasonable images can be produced, as long as the exposure time is not too long. Long exposures will simply give you a fogged image, due to the background light in the sky. In urban environments the sodium street lamps can cause the image to have an orange background glow, but the star images should show through.

· Trail images of stars that never set (called circumpolar stars) can be used to measure the length of the sidereal day – the time it takes the Earth to rotate with respect to the stars. This is one of the GCSE Astronomy List A coursework projects. The sidereal day is 23h 56m 4s.

· Finally you might need to experiment with exposure times and ISO levels (the speed of the ‘film’) to get the best results.

Finally a digital camera with zoom can take rather decent views of the moon.

Here is an example of a daytime shot of the waning gibbous moon taken 30 October 2007, at midday, using a Canon Sure Shot S70. Some lunar features can easily be made out using this simple, but effective, technique.

3 of 7