History of Long-Range Photography in Astronomy

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Slide 1

CCD Astronomy

Jeff Thrush

Slide 2

Optical Sensors used in Astronomy

Human Eye

For most of history the practical sensor has been the human eye.

Limited by Sensitivity

Physiological considerations and human subjectivity, placed serious limits on what could be discovered.

Photographic Films

The advent of photography in the last century was a monumental step forward in astronomy

It has the ability to record “unseeable” objects with long exposure times

Despite improvements, its efficiency remains very low.

For every 100 photons that strike the film, at best only three or four react with the silver in the film’s emulsion

Reciprocity failure

Slide 3

My Telescope “1979”

Slide 4

Optical Sensors used in Astronomy

Charged Coupled Device (CCD)

With better than 20% efficiency, they quickly won over the astronomical community

There sensitivity extends into the infrared spectrum

Its response to light is a linear function of incident flux and exposure time.

There is no reciprocity failure as encountered in long duration astrophotographs

Slide 5

A CCD camera can provide a personal window to the universe or total frustration

Slide 6

CCD Camera “Buzz” Words

CCD Arrays

Sampling

Pixels

Sensitivity

Pixel Binning

Blooming vs. Anti-Blooming

Readout Noise

Gain

Thermal Noise

Quantum Efficiency

Slide 7

The first questions you should ask yourself

What kind of imaging are you interested in doing

The selection of your camera depends strongly on whether you want a system tuned for planets or deep-sky objects. In most cases your telescope and mount will make this choice for you.

While a deep-sky system can certainly record planets, and a planetary system can image galaxies, the best results almost always come from systems customized for a particular task.

Slide 8

Deep Sky Imaging

The DEEP-SKY Camera must be:

Sensitivity

Low-noise

Some means of cooling the CCD

Peltier

Multi-pinned-phase mode (MPP)

A large detector (number of pixels verses pixel size)

600 pixel-square array with 20 micron pixels

1024 pixel-square array with 10 micron pixels