About the Author

About myself

Hi, I am Walter Koprolin. I may not be the typical amateur astronomer, as I have actually studied astronomy at the University of Vienna and finished with a doctorate. But let's start at the beginning:

I got interested in astronomy when I was about 17, my interest was probably kindled by a small department-store refractor which my family had stored in our garden-house. This had been purchased by my grandmother, back at the beginning of the '80s. Well, the views it offered were not really satisfying, as the optics were exceedingly bad; stars looked like planets as the scope was not able to show anything else but disks of light. Additionally, the mount was very shaky. However, I got curious enough to attend a basic astronomy course held by Hermann Mucke at Vienna's planetarium. During that course, another small refractor was introduced as ideal entry-level telescope, a 63 mm Zeiss Telementor achromat, back then still produced in Eastern Germany, and thus not expensive. A few weeks later, I found a sample of this telescope under the Christmas tree, along with a few astronomy books, and reasonable observations became possible for the first time.

As I grew older, my passion for astronomy, especially for extragalactic astronomy (I love those galaxies...) deepened, and I decided to study astronomy at university parallel to my course of studies in technical physics. I found studying astronomy easy and enjoyable, and got my master's degree in astronomy in 1997 and my doctorate in 2004. Both my diploma and my Ph.D. thesis where about extragalactics, what else would you think? ☺ My fields of research were the kinematics of early-type (elliptical and lenticular) galaxies, and the physical properties of the stellar population and the gas in Blue Compact Dwarf Galaxies.

During time, my collection of telescopes grew, but I have always specialized in scopes which are dedicated to astrophotography, or at least also usable in that regard. However I also enjoy using them visually. To read more about my telescopes, my current astrophotography setup and the equipment I use, see my Telescopes and Equipment page. For more history, see below.

My motivation for doing astrophotography has somewhat broadened during all those years: I wish to show the beauty and the science of astronomical objects and of the night sky in general to anyone who cares, to get people interested, even those who do not have or take the time to go outside and see for themselves. For there is rarely a more wonderful sight in nature than standing at night under a clear, dark sky far from any disturbing artificial light and seeing myriads of stars and the Milky Way running from horizon to horizon... That is why I like to go observing at remote sites, where it gets as dark as possible, there I feel somewhat closer to the sheer beauty of the sky.

In recent years, I have transformed from a mobile astrophotographer seeking "the very darkest skies" somewhere in the mountains to a backyard astrophotographer in light-polluted Vienna due to various reasons. However, weather permitting, I still go on an astrophotographic expedition high up into the Austrian Alps once a year, usually in September.

Photo of 2008, showing me astro-imaging with my favorite wide-field telescope, the JSO Wright-Newtonian, and a DSLR. No computers in the field back then!

My History of Astrophotography

It has been a long way.

Soon after I got my first telescope, I began to take my first astrophotos. I started with hand-guided telephoto lens photography, on chemical 35 mm film, with my father's camera, in 1990.

Astrophotography back then was in many ways different from today. I remained with telephoto lenses for a number of years, the camera and lens were mounted piggy-back on my newly-acquired 8" f/10 Schmidt-Cassegrain Telescope (SCT). This offered a drive in the RA axis only. I guided my photos manually using a crosshair eyepiece, spending hours in uncomfortable positions, trying to keep the guiding star split on the crosshairs - a tedious and tiring task, quite unthinkable today, when this task has long been taken over by autoguiders.

The go-to 35 mm camera body for semi-professional photographers in those days was the Nikon F3, and I had the good fortune of inheriting one of those, together with an array of lenses. Luckily this camera was designed with ruggedness and durability in mind. Mine for sure got used a lot and "made contact" with Earth during my astrophotography expeditions more than once, but it never failed to work until I sold it, with dents and all, after switching to digital photography many years later. I used it most of the time with Kodak Ektachrome E200 color slide (transparency) film, because E200 had a very standardized chemical development process, was sensitive to the red Hα line, had relatively fine grain, and was more accurate in color reproduction than any negative film. I scanned the slides after development to enhance them on the computer.

Realizing that the fork mount was not ideal for astrophotography, I upgraded to a Vixen GP-DX German equatorial mount, which had drives on both axes, and tried myself in primary-focus photography with an off-axis guider, still guiding manually. The manual guiding became even more tedious because of the increased focal length and the telescope's focal ratio was too slow. At f/10, my SCT was way too slow for really good results, and the photos of deep-sky objects I acquired back then can't stand up to modern standards. This, fortunately, did not stop my enthusiasm. In hindsight it was not a good idea to start my primary-focus astro-imaging career with a long-focal-length SCT, but those were the go-to telescopes of the 1990's and everyone seemed to have one of those big, shiny tubes. I purchased a f/6 focal reducer for the SCT later on, but this introduced really bad vignetting. It took me some years to acknowledge these facts and finally upgrade to my first good-quality 4" f/6.5 refractor, which soon proved much more adequate for astrophotography.

The tiresome hand-guiding days were finally over when I purchased a Meade Pictor 216XT CCD camera/autoguider, which was a bit cumbersome to use, but I was able to get nice round stars for the first time - whenever it worked correctly. Nobody else seemed to succeed with the Pictor as a stand-alone autoguider, but I managed it, and it remained in my service for more than 10 years. However, I can still remember frustrating nights when it wouldn't work as expected.

I left out some of the steps which more advanced astrophotographers took back in those late film days: I never upgraded to hyper-sensibilisized Kodak Technical Pan film, and I never upgraded to medium film format, and I never purchased a Schmidt Camera with its curved focal plane or the like. Looking back, I am glad I did not venture into those techniques which soon became outdated. I did, however, purchase a heavy German Equatorial Mount, the OTE-150, and still use it today. Yes, it is true that it doesn't find any objects in the night sky by itself and can't slew: I still like to find my astrophoto targets manually, being a bit old-fashioned and wanting to know my way around the constellations like a good visual observer.

In my opinion, the biggest step forward in astrophotography was the introduction of digital cameras to this hobby. I bought my first DSLR, a Nikon D70, in 2004 and modified it myself by replacing the original IR cutoff filter with an UV/IR cutoff filter better suited for photographing the red Hα line. The immediate first results were stunning (I still have some in my Gallery of Astrophotography, for example the Orion Nebula) and so much better than any result on chemical film that I soon sold my Nikon F3, which had accompanied me for so many years, and switched to digital imaging altogether, never looking back. It was one of those rare technological advancements which rendered all previous astrophotos inferior virtually "over night".

The advance of fast wide-field telescopes dedicated to astrophotography was another of those important steps forward. For me, it came when I bought my 4.9" f/3.8 JSO Wright-Newtonian, and quickly fell in love with this small exotic telescope in spite of its shortcomings like an inadequate drawtube and some degree of off-axis astigmatism. The results at such a fast focal ratio combined with a generously large field-of-view were new to me and unexpected. The quality I was at last getting at reminded me of Schmidt Camera results out of film days. I clearly have spent too many years with a slow, long-focal-length telescope, fighting all sorts of problems such as guiding, seeing and impossibly long exposure times. I then sold my SCT. I just wish I had arrived at small wide-wield telescopes much sooner. (Yes, it is true that I later found my way back to larger telescopes with my 9.5" Newtonian, but that is another story.)

The next step forward came with the advance of cooled CCD (later: CMOS) cameras dedicated to amateur astrophotography. This one was not as pronounced as the step towards digital imaging, but still, there is an advantage in using cooled sensors because of the thermal noise reduction. I started with a color matrix CCD and later added a monochrome CCD. Using CCD cameras came, however, with a drawback: Suddenly I found myself staring at a computer screen instead of the night sky. Before, I had not carried a notebook into the field: My autoguider was stand-alone, and the DSLRs did not require it. Now, it became mandatory, and my need for power supply in the field increased substantially.

My - to this date - final step forward in astrophotography was the introduction of narrow-band line filters. This was another game-changer for the photography of emission nebulae, because it freed me from the requirement of searching dark skies. With narrow-band line filters I could suddenly astro-image from my backyard, in the light-polluted suburbs of Vienna, and get good results. The most rewarding filter is Hα for most nebulae. The resulting images can be stacked with color images of the same object for HαRGB composites, presented stand-alone in their black-and-white beauty, or combined with [OIII] and [SII] narrow-band exposures for "near-natural" color images using a technique called tone mapping.

As for my philosophy in astrophotography, I go for esthetics, and not strictly for scientific content. A scientifically correctly reduced CCD image will not look very attractive. I use nonlinear enhancement for my astrophotos, trying to get as much faint structure and detail out of the deep-sky objects I photograph as possible, but I still want it to look natural and pleasing to the eye.