AUSTRALIAN PHOTOGRAPHY + DIGITAL SEPTEMBER 2015 AUSTRALIANPHOTOGRAPHY.COM 7
Star
Light
PHOTOGRAPHER
Andrew Campbell
My backyard in Burwood, suburban Melbourne, seems
an unlikely place to be photographing distant nebula,
but with the right tools, patience and many late nights,
images like this one are possible. This photograph of the
Seagull Nebula NGC 2327 was made using a 660mm
Williams Optics telescope and a QSI 683 Cooled CCD
astronomical camera. Unlike ordinary digital cameras
which have a Bayer RGB filter array over the sensor,
this astronomical camera has a monochromatic sensor.
To create a coloured image like this, you have to make
three separate exposures (often of several hours
duration) using three separate 5nm narrow bandwidth
filters (in this instance an Ha, an S2 and an O3 filter)
to capture light frequencies specific to chemical
signatures in the stars. The narrow frequency range of
these filters helps to eliminate the normal light pollution
that you get around a city. The three monochromatic
images are then assigned to RGB channels in
Photoshop to create this faux colour image. This same
technique is used by the crew driving the Hubble Space
Telescope! One of the big challenges is simply keeping
the telescope tracking the one tiny patch of sky for
several hours at a time, often over several nights so you
can overcome the signal-to-noise ratio and get enough
photons onto the sensor to get a good exposure. This is
where having a solid tripod and a decent equatorial
tracking mount really becomes important. I first got
interested in astro-photography three years ago, but it
took at least six months to get my head around the
science, maths and processing that go into capturing
images like this. Over the past two years though, I have
been more consistently capturing images that I’ve been
happy with and last month one of my images was
successful in winning the Central West Astronomical
Society’s Prestigious David Malin Deep Sky award.
With a folio of four of these images I was also named
the AIPP Victorian Science, Wildlife and Wild Places
Photographer of the Year for 2015.QSI 683 CCD CAMERA, WILLIAMS OPTICS
660MM F5.6 LENS, 15.3 HOURS (OVER SEVERAL
NIGHTS), F5.6.