Topic: Astrophotography

Speaker: Doug Paul

Description: Astrophotography can be divided into two classes. The first class is basic photography using a fixed tripod. This allows the brighter objects (e.g. the planets out to Saturn) to be imaged, but the exposure time is limited by the earth's rotation. The second class allows longer exposures by using tracking mounts that cancel the rotation. Deep Space Objects (DSOs) can be very dim, requiring minutes or hours of total exposure time built from a number of shorter sub-exposures ("subs"). The individual subs are processed to remove systematic noise, aligned and stacked to create a RAW image. Lastly, the RAW image usually needs to be stretched to bring out the details and reduce the dynamic range so the image can be displayed.

Doug Paul has been an amateur photographer for most of his life and is a retired electrical engineer. He has used his professional skills to understand the processing of astronomical images and to write programs for image acquisition and processing. The talk will chronicle his path from landscape photographer to DSO imager using a standard DSLR and lenses. He will then describe the techniques used to produce DSO images.

Location: Common Room, First Parish Church Bedford, Elm Street Entrance