Catch the Sun

ASTROPHOTOGRAPHY CAPTURE | Take the perfect astrophoto with our step-by-step guide | How to safely capture the drama now that solar activity is picking up

- Pete Lawrence

The Sun has been showing increased activity over recent months and with its position in the sky now optimal from the UK, this is a great time to review some of the techniques required to image it. Solar imaging isn't without risk, and concentration needs to be high at all times to avoid accidents. It goes without saying that you should never look directly at the Sun nor point any instrument at it without using appropriate filters.

The two most common ways to view the Sun using a telescope are in white light or with a solar narrowband filter. Ready-made white-light filters are available or you can make your own (following instructions provided by the supplier).

Narrowband filters are more expensive and can be either built into a dedicated solar telescope or supplied to convert a night-time telescope, typically a refractor, into a speciality narrowband instrument. Common narrowband filter types offer views in hydrogen-alpha or calcium-K, the former being the most common. Other wavelengths are also available.

White-light filters show photospheric phenomena such as sunspots, sunspot groups, faculae, limb darkening, solar granulation and very rarely - solar flares. Features in white light tend to change in form subtly over the course of a few hours or days.

H-alpha filters reveal chromospheric and inner atmosphere (corona) features including active regions, plage, spots, spicules, filaments, fibrils, dark mottles, prominences and flares..