Adventures in Astrophotography
By Kerry-Ann Lecky Hepburn
My interest in astronomy started from a fairly young age. For as
long as I can remember I have had a real fascination with the wonders
of the universe and the countless number of objects in the night sky.
Those objects varied between beautiful, intricate, and
mysterious. After getting my first telescope at the age of 11
and then my first serious film camera as a teenager I began to think of
the possibilities of astrophotography. Over the course of more than
15 years I dabbled in it, but it wasn’t until the beginning
of this year (2007) that I have made some huge leaps in the hobby. I
became seriously hooked.
The early years:
My first ever astrophotos started with my decision to do a high school
science fair project on variable stars back in 1990. I figured that if I hooked up
my Minolta SLR 35mm film camera to my 4.5 in Newtonian reflector with
the help of a t-ring and t-adaptor, I could take a single second timed
exposure of the variable star, Algol, over the course of a few months. The
varying diameter of the star on my photo could possibly show how
it changed in brightness.
First telescope: 4.5in newtonian reflector
Algol
The planets and the moon were also fine targets for me to try. I
thought that with planets I would have to take long exposures to
capture them, but later found after getting my pictures back
that that was not the case. I also realized that the planets moved too
quickly for my 4 second long exposure, especially with no tracking on
my rickety equatorial mount.
First Jupiter and Venus images
Again with the moon I varied the exposures but they were still
overexposed since I had no formulas at hand giving me an idea of what
times would be ideal. The photos below were taken during a lunar eclipse.
During my university years, I spent a half a year as a volunteer
at the observatory. I was able to take advantage of a fully
computerized 30 cm telescope. I only took photos on a couple of
occasions by simply hooking up my Minolta 35mm SLR camera with my t-ring
and the observatory's t-adaptor. I took my first successful astrophotos
that I could say I was proud of for a very long time. Those
shots were only single exposures. I guessed at exposure times
while using cheap Blacks ISO1600 film.
Comet Hyakutake and M42
Since I didn’t have access to the observatory telescope whenever I
wanted and my Newtonion telescope was no good for photographing objects
other than the moon, I opted to start concentrating on photographing
widefield targets. With my camera and 50mm lens on a simple tripod, a
30 second exposure with high ISO film yielded fairly good results.
The year of leaps and bounds:
2007 was when I really wanted to try my hand at long
exposure astrophotography through the telescope. I did a bit of
research and found the best deal that I could find for an entry level
motorized mount and a scope with reasonable amount of aperture that
would be a nice upgrade to my 4.5 in Newtonian. I settled on the
Celestron 6in Schmidt Cassegrain telescope on the CG5-GT (ASGT) mount.
This scope, combined with my Canon 300D digital SLR camera, would
provide the stepping stone I needed to get into more serious
astrophotography.
There was a bit of a learning curve to start because in order to get
the GOTO features and tracking to work properly, I needed to
learn about polar aligning. Once I got that figured out I started
taking short exposure images of bright objects like the moon and Saturn.
“First light” images
Once I got the setup and aligning all figured out over several nights
on my balcony. I took my scope out to a dark sky site in April for my first
observing session with my local astronomy club. I always read that the best way to get
into really long exposure photography was to piggyback your camera and
lens on a mount that tracks. I then took images of Venus, Pleiades, and
Orion’s Belt. It turned out well and because I was using a wide
angle lens I was able to get exposures up to 3 minutes without seeing
star trails.
After a very short while of piggybacking, I felt the need to try those
long exposures through the 6in SCT. However, because of the higher
magnification and smaller field of view, I knew I would need very
accurate tracking if I wanted to image objects that are faint. Having a
motorized mount like the CG5-GT was great but not quite
good enough. I would need a way of precisely guiding a single star so
that the errors in the drive and tracking would not be noticed on the
long exposure images. I did a lot of research online, reading the many
pros and cons of various methods of guiding and finally came to the
decision that the way to start would be to buy a second small
scope (Sky-Watcher Equinox 80mm) that I could mount side by side with
the 6in SCT. So while
my camera was hooked up to the 6in scope, a guiding eyepiece called a
reticle eyepiece with illuminated cross-hairs would then be used with
the 80mm scope to ensure that a star in the field of view stayed on or
near the cross-hairs. The hand controller would be used to slew the
mount in which ever direction needed to accomplish this. After
practicing this for some time, keeping in mind some tips that a fellow
astrophotographer gave me, I was able to take a few long exposures of
one of my
favourite galaxies M51. After taking a few long exposures and loading
them onto the computer, it occurred to me that I would be faced with
another difficult feat.... image processing. Knowing that the more
images you take the more you can increase the signal to noise ratio, I
manually stacked the images in Photoshop and then made a few
adjustments to the levels and saturation and voila....
I was really proud of the fact that it actually looked better than what
I saw in the eyepiece and my husband was amazed that I
was able to capture such an object from home. That was
enough to keep me going.
Into the early summer, I continued to practice this method. I even
tried
imaging with the 80mm telescope on large targets while using the
reticle eyepiece
in the 6in scope for guiding. The results looked much sharper. The
images from the 80mm's larger field of view, did not show as much
error from my manual guiding because the field of view was much larger
than the 6in. I also started to take dark and flat frames to help
minimize noise and vingetting. In addition I improved my processing by
finding a free program (Deep Sky Stacker) on the net that easily stacked all those frames
in a way that gave me a drastically cleaner looking final image.
Although there is a great deal of satisfaction with manually guiding, I
found it very tedious. A few to several minutes staring at a faint star in the
eyepiece with the fingers practically pasted onto the hand controller, I
eventually got cramps in my neck, leg and back. I also love observing
and felt I was missing out by spending all my time staring at this one
star. I began to consider the auto-guiding route. I did a bit of
research and realized that all I would need is a cheap webcam or
imager. I already lug my laptop with me into the field so why not lug
around one more item plus a few more cables? I was recommended the Deep Sky Imager (DSI) because of its sensitivity
to fainter stars. I bought it from him for a good price and
immediately began to work on reconfiguring my astrophotography setup.
I had to first get my CG5-GT (ASGT) mount to communicate with my laptop
via the RS232 cable and ASCOM platform (many astro programs require
ASCOM in order to communicate with the ASGT mount). I then loaded a
freeware program called PHD Guiding which was able to communicate with the
DSI and my mount. A few clicks of the mouse a bit of DSI focussing on a
single star and a few more clicks and I was on my way. I was surprised
at how easy autoguiding was to get running after getting the initial
communication bugs worked out.
First autoguided image
New setup (Starfest 2007)
I was pretty happy with my images but still thought it could impove. I
wanted crisp stars, and a smoother dark background with more faint
features making it through the final image. I kept getting tips from
fellow astrophographers, encouraging me to take many more frames.
With my initial setup this task would have been very difficult but now
with my computer doing much of
the work in terms of timing exposures and guiding, I felt like it was
definitely possible. The results were astounding to me when I was
able to combine the accuracy of autoguiding and the improvement in
signal to noise ratio from taking 15+ frames which were a few minutes
in length each.
Image collecting is only half the battle when it comes to
astrophotography. The other battle is image processing. Sometimes
I actually find it takes way more effort and time processing an image
than it does setting up your telescope and collecting the
frames. I did some research online to try to improve on my
processing, but I didn't notice a huge change until I went to an image
processing seminar at Starfest (Canada's largest star party). I learned how to better use layers,
levels, curves, filters and saturation in a way that brought out even more
detail and colour.
I have also learned about stacking several sessions of images to
make one master image that can have a total of several hours of
exposure times. This can make a phenomenal difference as you can see
below
M31 first night 15x3min = 45min total
M31 first and second night combined ~2hrs total
Prior to this Fall, most of my astrophotos were taken with the Canon
300D. It proved itself to be a very capable camera for daytime
and nighttime photography, but with so much time and energy being spent
on this hobby of photography it made sense to finally upgrade
when I found out that Canon had come out with the new 40D. With its'
liveview capabilities I am now able to get focussed much faster and
easier. The higher resolution, lower noise, absence of amp glow,
and
increased image transfer speed have really added another level of
ease and improvement.
So now I am nearing the end of a great year of astrophography. I have
learned that it takes a great deal of patience, research and dedication
to accomplish this task. The joy of seeing a beautiful night sky object
appear before your eyes during the image collection and then
after the processing process, is so incredibly satisfying that it will
likely hook you in for a long time to come. I feel I can now say
that am well into my journey to
capture the wonders of the night sky.
Back To Kerry's Astrophotography page