Astrophotography, or “imaging” as
it’s usually called by those in the hobby, can be both rewarding and a bit
challenging. Technology has revolutionized all aspects of astronomy. Today’s
amateurs can take better images with specialized digital cameras than professional
observatories could using the old film technology of just a few years ago. It’s
really easy to hold a cheap digital camera up to an eyepiece and take a great
image of the moon. But, if you’ve got any geekness inside you, don’t do it! You might get caught in
the world of imaging. It can become an all-encompassing endeavor eating up
countless hours while making your bank account vanish. Although you can start
with relatively inexpensive hardware and free software, you’ll progressively
want more expensive cameras, bigger telescopes, better mounts, and fancier
software. It’s an addiction that never ends. Plus, there can be a fairly
lengthy learning curve involved in this hobby and a million things can (and
do)
go wrong, so don’t even think about it unless you’ve got an amount of patience
and perseverance that borders on masochism.
If it’s so challenging and
expensive why do I do it? Perhaps it’s because it isn’t easy. Perhaps because
it reveals a universe we can’t otherwise experience. And I get to do it myself,
with my equipment, in my backyard, without relying on some massive government
project. There’s a popular belief that high magnification is required. Of
course this is true for many objects, but most of the images I take magnify
objects just 10 to 50 times (if printed on 10”x8” and held a couple feet
away).
This isn’t a lot. Many deep sky objects viewed by amateurs are fairly large;
some are several times larger than the full moon. But they are very dim
requiring the hardware to gather much more light than the human eye can detect.
My 12.5” telescope obtains 2300 times more light, a digital camera can increase
this by a factor of 50 times, and a 5 hour exposure increases it by an
additional factor of 500,000. I can’t think of another field capable of over a
50 billion times amplification. Perhaps it’s just the technical challenge.
Regardless, I find it very rewarding (yes, I may be a bit crazy – it’s
practically a requirement in this hobby).
When I started taking digital images, I was amazed at what I could see
with a camera compared to an eyepiece. Visual astronomy requires a very dark
site with absolutely no stray light destroying your dark adapted eyes. Of
course, dark skies are always an advantage, but a camera doesn't care about
that street light down the block. Cameras are always ‘dark adapted’ and they
are better at capturing photons. To record dim objects you need to take long
exposures. Our eyes gather light for only about 1/30 of a second before
resetting our mental image while a digital camera can build up an image
practically forever. A simple 10 second exposure gathers roughly 300 times more
light than our eyes can capture with an eyepiece on the same scope – and that’s
not including the fact that the camera is over 50 times more efficient at
detecting photons. I initially took a lot of 10 to 60 second exposures each
evening. The images were crude with lots of noise but the objects were far more
recognizable than what I could see using an eyepiece. I'd brag about how many
objects I captured. Two or three dozen during the evening wasn't unusual. Now I
realize how foolish that was. The images recorded by a camera can last forever
so why not take extra time and strive to make them look as good as possible.
Better images require longer exposures. I now know the figure of merit isn't
"how many images per night" but rather "how many nights per
image". I usually use exposures of 5 to 20 hours. Obviously, this can’t
always be done in a single night. Given daylight, clouds, rain or snow, and
perhaps a full moon coupled with some objects only being visible part of the
night, it may actually require several days, weeks or sometimes even months
just to get sufficient time with the right sky conditions (I told you
patience is required).
How can such an exposure be made? Well one benefit of today's digital world is
that we can get the advantages of a very long exposure by combining many
shorter exposures. I may take as many as fifty or sixty 10 minute exposures
throughout a night's session and repeat this over several nights. I then tell
my computer to add all the good ones together after discarding the images where
something went wrong. This effectively gives me a very long exposure without
worrying about shifting clouds destroying the image or a plane, satellite or
meteor going through my field of view (all very common). Yea, there's actually a
lot required to make this happen. But that's what makes it challenging.
I’m not a novice and clearly not an
expert. Guess that makes me a fairly typical deep sky imager - at least among
those serious about the hobby. I started the activity shortly after collage (many
years ago) when Celestron came out with their C8 Schmidt-Cassegrain scope. This
very popular little 8” orange scope revolutionized amateur astronomy and
eventually led to today’s fantastic equipment. In those days imaging meant
using specially hyped film with hours of manual guiding just to get something
vaguely similar to what you’d see in magazines. Well it was just too hard for
me. I put the scope away until I discovered the new world of digital imaging. I
followed the rule of acquiring ever more expensive hardware starting, like many
others, with a classic 10” Meade LX-200 scope and an SBIG 7E camera. Then, like
everyone, I slowly improved my equipment getting a better camera, mounting the
scope on a better mount and finally getting a better scope. I’ve now got some
great hardware including an Astro Physics AP-900 mount on a permanent pier, a
Rainbow Astro RST135E portable mount, Takahashi FSQ-106 4” refractor, Planewave
12.5” CDK scope, and Finger Lakes Proline 16803 camera. Better equipment
doesn’t necessarily lead to better images but it does mean less effort is
required. Someone starting out in the hobby today has the advantage of an
explosion in the availability of really good hardware and software at very low
cost that’s occurred over the last few years. This has made the hobby much
easier and far more affordable.
I specialize in deep sky images.
This means galaxies, star clusters, super nova explosions, planetary nebula,
and emission, reflection and dark nebula (the clouds of space). Although
I have many great Televue eyepieces, I almost never use them. I just can’t see
observing a dim fuzzy blob when you can get great images through digital time exposures. And since everything is
computer controlled I can do it in a nice warm living room in the winter or
hiding from bugs in the summer. I also don’t do much solar system work.
Imaging planets or the sun uses a totally different process than deep sky
imaging. I do have special filters for the Sun and several good video cameras
key to solar system imaging, but for some unknown reason haven’t done much with
them.
Deep sky imaging is dependent on
equipment, processing skill and sky conditions. I have good equipment and am
working on my processing skills but there’s no substitute for dark steady
skies. Unfortunately, my sky is neither dark nor steady. I use 2 observing sites. Most images are
taken at my home 60 miles north of New York City. Observing conditions are not
the greatest. I have limited sky visibility, considerable light pollution and
poor seeing. Surrounding trees hide altitudes under 35 degrees to the east and
55 degrees to the west with a visual magnitude limit of about 5.4 at best. It’s
rarely that good. In fact, I usually have a hard time spotting the magnitude 2
star, Polaris. It’s normally a class 6 location (orange) on the
Bortle scale, occasionally moving into class 5. Summer images are often taken
at a location 144 miles further north. Here the sky is better at about a 6.3
visual magnitude and the Milky Way is clearly visible with a lot of detail.
However, thanks to a nearby lake, there is a lot of water vaper in the air
which often fogs up after midnight significantly limiting imaging time. I’m
often asked “how can you do astrophotography with these sky conditions”. I know
my images will never compete with those taken from a better site. But, this
hobby is about enjoying what you can do yourself, even if it isn’t the best in
the world – just like every other hobby from playing golf to painting
landscapes.
I consider both locations to be
semi-permanent. They both utilize a fixed pier with all equipment mounted 24/7
but not contained within a permanent structure. I use a TeleGizmos 365 series
cover plus a garden variety Home Depot brown tarp to protect the
equipment. Power supplies and all
electronics, including a headless computer (no monitor or keyboard), are
contained in a simple box hung on the pier. This keeps cables short and organized
with a simple bundled cable set feeding the camera/focuser/heater units and a
second bundled cable set feeding the mount. This computer runs all the software
controlling the scope, mount and cameras plus a couple of weather stations
monitoring clouds, darkness and rain. A LAN connection allows remote control of
the system using VNC software. I use a remote laptop to setup a night’s
operations then usually an iPad to periodically monitor or modify operations.
Occasionally I’ll use my iPhone when I’m away from home.
I use software popular with many
deep sky imagers: Windows 10 Pro with TheSkyX planetarium software, ASTAP for
plate solving, PHD2 for guiding, NINA for image capture, MaxIm for image
calibration, CCDStack for stacking and initial stretching, and Photoshop with a
bit of PixInsight for image processing. NINA lets me run the whole thing while
I get a good night’s sleep. It can automatically sequence through the objects
I’ve selected with the appropriate filters, focus the scope, rotate the camera
as needed, correct for pointing errors, select guide stars, make calibration
frames, and of course take the images that I can process the next day.
I can fully understand why multi-hour exposures
or processing with complex programs like Photoshop or PixInsight might not be
for everyone. But that doesn’t mean you need to suffer looking through an
eyepiece at dim ill-defined blobs. Sometimes I attach a digital camera to a
scope and just take short exposures of just a few seconds. Visual Imaging is
the name I use to describe using a camera to see more than what most scopes
offer with an eyepiece but without spending the time or effort to make pretty
pictures. This is sometimes called Electronically Enhanced Astronomy, EEA, or
Electronically Enhanced Visual Astronomy, EEVA, or Observational
Astrophotography. A highly binned monochrome astro camera works best but a
normal DSLR or mirrorless camera is fine. The scope could be as simple as a
DSLR lens attached to an inexpensive tracking device on a standard camera
tripod. Objects are then viewed on a computer, tablet or camera screen. As I
said before, the camera is far better at capturing dim images than the human
eye. This configuration lets me enjoy many of the sights available in the night
sky with clarity but without complexity. They won’t be as impressive as the
processed long exposure photos seen in magazines but galaxies, bright nebula
and larger planetary nebula actually look like they should. Visual imaging is a
simple way to enjoy deep sky astronomy and in my opinion more rewarding than
using an eyepiece.