Sky & Telescope - June 2024 - 56

JUNE 2024 OBSERVING
First Exposure
pHORSEHEAD PORTRAITS This pair of identical, 30-second frames illustrates the difference between the results produced by a regular Canon
EOS R (left frame) and an astronomy-friendly Ra camera (right). While the reddish hydrogen region surrounding Orion's dark Horsehead Nebula appears
in both shots, it's far more pronounced in the Ra camera's image.
as tiny pinkish knots of nebulosity in
the Milky Way.
While a regular camera will certainly
record bright nebulae as faint
pink highlights, a camera that has
been modified to be more sensitive to
hydrogen-alpha wavelengths will pick
up these details far more readily.
Filtering Fun
A dedicated astronomy camera is rarely
used without adding at least one filter
in front of its sensor. As it happens,
your camera already has a filter built in
to reduce IR and ultraviolet (UV) light.
If it didn't, your daytime images would
include a lot more red than you can
see and even allow some UV to intrude
into the photo. Aside from producing
flat and blown-out images, it's also
likely your camera's lenses wouldn't be
able to cope with such a wide range of
wavelengths, resulting in pictures that
appear a little out of focus as well.
So, the presence of a UV/IR filter is
great for daytime photography, but it's
not ideal for shooting certain objects in
the night sky. That's why your camera
will only barely register nebulosity in
many astronomical targets. Thankfully,
you're not stuck with the stock sensor
filter - you can replace it with one that
still blocks UV and IR light but lets the
valuable hydrogen-alpha wavelength
pass through. Milky Way images or
even portraits of constellations such
56 JUNE 2024 * SKY & TELESCOPE
as Orion or Cygnus really pop when
regions of glowing hydrogen gas are
also captured.
Plenty of YouTube videos and online
instructions will show you how to disassemble
your camera and replace the
standard built-in sensor filter with one
more suited to astrophotography. But
it's tricky work. In fact, I'll confess that
the very idea of messing with my camera's
delicate sensor terrifies me. (If you
ever saw me with a screwdriver or power
tool, it would terrify you, too!) And I'm
not alone in having this fear. Thankfully,
a few people gifted with steady
hands and experience will modify your
camera for a reasonable fee. Two firms
that offer this service are astrogear.net
and kolarivision.com. A Google search
will turn up several more.
I took advantage of this approach
myself with my original Canon EOS
Rebel. I was nervous about surrendering
my DSLR, but once I got it back
and started shooting, I wondered why
I'd waited so long! I even purchased
a brand-new Canon 5D Mark II and
nervously sent it to a gentleman by the
name of Hap Griffin, in South Carolina,
for a warranty-voiding modification. I
have no regrets.
You can find plenty of mod-ready
cameras on the used market, or maybe
you've recently upgraded and already
have a second camera that doesn't see
much use anymore. Another option
is to turn to a company such as
nightskycamera.com or hutech.com,
which sell new, pre-modified " spectrum-enhanced "
cameras and include
warrantees.
What's the Catch?
Shooting the night sky with a modified
camera is an amazing experience, but
there are a few things you should know
pIN THE PINK Shooting daytime photos with a modified camera requires a manual white-balance
adjustment to avoid a pink color cast to your images. The difference is obvious in this pair of
images shot with a modified Canon EOS Rebel DSLR.

http://www.nightskycamera.com http://www.hutech.com http://www.astrogear.net http://www.kolarivision.com

Sky & Telescope - June 2024

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