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Since the early 1990s renowned Astrophotographer Bob Fera has worked alongside his wife Janice to produce some of the world's most jaw-dropping images of the night sky.  Here, Fera explains exactly what is meant by astrophotography, and he outlines the types of cameras and optical equipment he finds are the best for capturing deep space images.

Astrophotography equipment

As Fera explains, put very simply, astrophotography is the art and science of photographing the night sky.  The discipline can range from using a simple single-lens reflex (SLR)-type camera on a tripod to record star trails, to high resolution images of the moon and planets, to so-called "deep-sky photography," long exposure images through a telescope of faint objects like nebulae and galaxies.

"Deep-sky photography is what I do," says Fera.

While it is possible to use digital SLR cameras (DSLRs), Fera prefers to use a type of CCD camera that is specifically designed for Astrophotography.  The U16M camera, manufactured by Apogee Imaging Systems, contains a 4096x4096 pixel monochrome detector that is about 36mm square.

The telescope, a Ritchey Chretien Cassegrain, has an effective focal length of 3046mm, made by Officina Stellare in Italy. Image courtesy of Bob Fera
The telescope, a 14" Ritchey Chretien Cassegrain, has an effective focal length of 3046mm (appx f/8.5), made by Officina Stellare in Italy.

"To take colour images I have to shoot separate sets of exposures through red, green and blue filters and combine them into a colour picture on the computer," says Fera.

To complement the camera, Fera also uses a range of other equipment at his home under the dark skies of Foresthill, California (US), including an Officina Stellare 14" f/8 Ritchey Chretien Cassegrain telescope.  The Hubble space telescope itself uses the Ritchey Chretien Cassegrain (RC) configuration and, according to Officina, the RC range is the "most widely used optical scheme by professional astronomers and astroimagers all over the world." 

To complete his set-up, Fera also uses an Astro-Physics 1200GTO German Equatorial Mount, a Clement Bellerophon Focuser, Astrodon LRGB and H-alpha Filters and an Astrodon Monster MOAG Off-axis Guider.

Equipment mounted on the Ritchey Chretien Cassegrain telescope. Image courtesy of Bob Fera.

The apparatus hanging off the back, starting at the scope and moving away is as follows: Motorized and computer-controlled focuser; Off-axis Guider with a secondary CCD camera used for tracking long exposures; Filter wheel containing 5 50mm square filters (clear, red, green, blue and "narrowband" Hydrogen-Alpha); Apogee U16M CCD camera.

Advanced cooling systems

According to Fera, the type of camera he uses is specifically designed for low-light, long exposure work.  They have very advanced cooling systems that can cool the CCD up to 50-60 degrees C below the ambient temperature to reduce noise, which Fera points out is a critical feature.

"In addition, most advanced astrophotographers use monochrome cameras, which gives us the full resolution of the chip.  One-shot-colour cameras use a Bayer Matrix that effectively reduces the resolution because they use three pixels on the chip to record one pixel of data," he adds.

Because he focuses solely on deep-space photography, Fera explains that he has no need to change the camera and optical equipment he uses depending on the type of image he wants to capture.

"I have only the one camera, and I do only the one kind of photography," he says.

M81 - Spiral Galaxy in Ursa Major. Image courtesy of Bob Fera
M81 - Spiral Galaxy in Ursa Major. 

"However, most good lunar and planetary photographers do use different types of cameras for those applications.  Typically they use something like a webcam that can take thousands of frames very quickly.  The sharpest of these frames are combined together to get a high-resolution final image," he adds.

Written by Andrew Williams, Contributing Editor, UK, Novus Light Technologies

All images courtesy of Bob and Janice Fera.

Labels: aerospace,astrophotography,telescopes,cameras,CCDs

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