Written by Mr. WONG Hin-fan
Any camera with a "B" shutter may be used. Single lens reflex camera is the best choice since its lens is interchangeable and can be adapted to a telescope. The choice of lens depends on the size and brightness of the celestial body photographed. Lenses ranging from fisheye to super telephoto can all be used. Other accessories include tripod, shutter release cable, adaptor ring, equatorial mounting, guiding telescope and cross-hair eyepiece.
When taking photographs of the Sun , the slowest film of speed ISO25 is used. For Moon, lunar eclipses and total solar eclipses, film of speed from ISO100 to ISO400 is suitable. Whereas film of speed from ISO400 to ISO3200 fits for shooting star field, the Milky Way, nebulae, star clusters, galaxies and comets. Recently, the use of ISO800 colour negative film has been very popular because of its high sensitivity, fine grain quality and good balance.
As the right combination of exposure time and aperture varies for different celestial objects shooted and equipment used, bracket exposure (two stops either way) is recommended in order to find out the best exposure time. Every technical data must be clearly recorded for future reference.
Since the partition between successive frames may not be apparent for film of astrophotographs, taking a daytime photo or a flash photo before start is recommended to fix the first frame. To avoid improper cutting of the film by processing store, "DON'T CUT FILM" should be specified.