Celestron CR-150 HD User Manual download pdf (Page 27)

Telescope Basics • 27

Your Celestron telescope can be used for both terrestrial and astronomical

photography. Your telescope has a fixed aperture and, as a result, a fixed f/ratio.

To properly expose your subjects photographically, you need to set your shutter

speed accordingly. Most 35mm single lens reflex (SLR) cameras offer through-the-

lens metering that lets you know if your picture is under or overexposed. This is

important for terrestrial photography where exposure times are measured in

fractions of a second. In astrophotography, the exposures are much longer,

requiring that you use the “B” setting on your camera. The actual exposure time is

determined by how long you keep the shutter open. More on this in the section on

“Celestial Photography.”

To reduce vibration when tripping the shutter, use a cable release. Releasing the

shutter manually can cause vibration, something that produces blurred photos. A

cable release allows you to keep your hands clear of the camera and telescope, thus

reducing the possibility of shaking the telescope. Mechanical shutter releases can be

used, though air-type releases are best.

General Photography HintsGeneral Photography Hints

General Photography Hints

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Celestron CR-150 HD User Manual Page 27