Gallery of Astrophotography and CCD-Images

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Important info:

In this gallery, I (Walter Koprolin) present my best results in astrophotography. Most the images which can be found here were taken using CCD and CMOS sensors built into camera bodies dedicated to astrophotography and DSLRs modified for the needs of amateur astronomers.

The Showcase

A new way to experience this website is The Showcase, which contains thumbnails and links for a selection of my very best astrophotos.

Deep-sky objects, planets, comets and nightscape photography - Just click on an image to enter the object category

Photos of Galaxies
Photos of Globular Clusters
Globular Clusters
Photos of Galactic Clusters
Galactic Clusters
Photos of Galactic Nebulae
Galactic Nebulae
Photos of Supernova Remnants
Supernova Remnants
Photos of Star Fields
Star Fields
Photos of Planetary Nebulae
Planetary Nebulae
Photos of the Solar System
Solar System
Photos of Comets
Dusk, dawn and startrail photography

Special Objects and Events - Just click on an image to enter the event

Photos of the Venus Transit 2012
The Venus Transit, June 6th, 2012
Photos of Comet Garradd
Comet Garradd
Photos of the June 2011 Total Lunar Eclipse
The June 2011 Total Lunar Eclipse
Photos of the January 2011 Partial Solar Eclipse
The January 2011 Partial Solar Eclipse
Photos of Comet Machholz
Comet Machholz
Photos of the Venus Transit 2004
The Venus Transit, June 8th, 2004
Photos of the November 2003 Total Lunar Eclipse
The November 2003 Total Lunar Eclipse
Photos of the Aurora Borealis on November 2003
Aurora Borealis in November 2003
Photos of the May 2003 Partial Solar Eclipse
The May 2003 Partial Solar Eclipse
Photos of the Mercury Transit 2003
The Mercury Transit, May 7th, 2003
Photos of Comet Ikeya-Zhang
Comet Ikeya-Zhang
Photos of Tenerife's Teide Observatory
The Teide Observatory at Tenerife
Photos of the January 2001 Total Lunar Eclipse
The January 2001 Total Lunar Eclipse
Photos of the August 1999 Total Solar Eclipse
The August 1999 Total Solar Eclipse
Photos of Comet Hale-Bopp
Comet Hale-Bopp
Photos of Comet Hyakutake
Comet Hyakutake

About these images...

Here I (Walter) describe my astrophoto setup, my equipment, and imaging techniques. Links within this part are external and point to various manufacturers.

Table of Contents:


For taking most of the astrophotos found in this gallery I used one of three different telescopes:

    TMB 4.1" f/6.2 APO and guidescope in astrophotographic use

    For standard wide-field imaging the TMB 105 (shown in the photo mounted side-by-side with the Telementor refractor, which is used as guidescope), which is a 4.1" f/6.2 Triplet APO refractor with optics designed by Thomas M. Back / USA and sold for Europe by APM Telescopes in Germany. My version of this superb refractor has a heavy German-made tube. For astrophotography, a flatfield corrector is mandatory, I use the TMB flatfield corrector which is optionally sold with this telescope. It is designed for medium format, so I use a custom-made adapter for my CCD and digital cameras.

    JSO 4.9" f/3.8 Wright-Newtonian and guidescope in astrophotographic use

    For extreme wide-field photography the JSO 4.9" f/3.8 Wright-Newtonian (shown in the photo below the guidescope). This rather exotic telescope is designed as astro-camera and was produced by Japan Special Optics Co., a company which ceased to exist around 1996. I got my sample used from a long chain of predecessors. At f/3.8, and with a focal length of 475mm, it is very well suited for digital camera photography of large nebulae and Milky-Way structure, the results often have Schmidtcamera-like quality.

    9.5" f/4.9 Newtonian in astrophotographic use

    For medium focal length photography a 9.5" f/4.9 Newtonian. Its optics were purchased from Orion Optics UK via Teleskop-Service, while the tube assembly was custom-made by a friend, who is a mechatronics expert. A TeleVue Photographic Paracorr corrects for coma and boosts the focal ratio of this scope to f/5.6, so the effective focal length of the Newtonian is 1356mm. The secondary mirror has a small diameter of 3.5".

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My primary mount for astrophotography is an OTE-150 (2002 version), which is a mid-weight German Equatorial Mount produced in Germany. It may not look attractive, but it is rigid, and its drives run quite smoothly with a built-in mechanical periodic error correction. This mount handles the small telescopes well, even under windy conditions; better than the VIXEN GP-DX, which is still in use as secondary mount for astrophotography with small telescopes and for visual observations. However, the 9.5" Newtonian plus guidescope, camera, autoguider and other accessories pushes the OTE-150 mount to its limits.

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The OTE-150 is mounted on a massive wooden TS Stativ Deluxe tripod, mine is designed to handle Newtonian reflectors and can be loaded (in theory) up to 120 kg. The GP-DX is mounted on a pointed Baader hard-wood tripod which I usually ram deep into the ground to quickly damp any vibrations.

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For photography, both mounts can be controlled by a PowerFlex MTS-3SDI, which features everything an astrophotographer really needs: Fully programmable drive speeds, microstep mode, periodic error control, backlash compensation in declination, a (non-standard) autoguider port, PC interface and (at least in theory) GOTO capability, i.e. the ability to point automatically on objects, when connected to a computer. It is produced by Boxdörfer Elektronik in Germany. For visual observations an older version of the PowerFlex MTS-3SLP, which I also own, is sufficient.

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Currently I use two special CCDs for astrophotography: A monochrome and a color camera.

The monochrome CCD is an ATIK 383L+ which features a Kodak KAF-8300 sensor with 3362 x 2504 effective pixels (8.4 megapixels). The pixel size is 5.4μm x 5.4μm, the bit depth 16 bit. This is a superb sensor which worked right from the start and never gave me any kind of problems. It has a mechanical shutter and cools down to a maximum of -40 degrees below ambient temperature, the chip temperature is regulated. The ATIK is used for taking deep luminance frames in the field, and in combination with narrow-band filters (see below).

My color CCD is a ZWO ASI294MC Pro. It is equipped with the Sony IMX294CJK CMOS sensor which has 4188 x 2822 pixels (11.8 Megapixels). The pixel size is 4.63μm x 4.63μm and the bit depth of 14 bit. The ZWO ASI is a one-shot color camera with an RGGB bayer matrix on the sensor. It can be cooled down to -35 degrees below ambient temperature, the chip temperature is regulated. I like to work with a gain setting of "0" to make use of the camera's maximum 63700e- full well capacity, and take longer exposures up to 10 minutes when I have dark skies.

Older color images were taken with a QHY8 Pro. While basically a good camera, and cheap as CCDs go, it had a few drawbacks, most annoying was its tendency to collect dew (and occasionally ice) on the CCD window and - additionally - on the sensor itself once its temperature drops below 0°C.

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Occasionally I am astro-imaging in my backyard at home in Vienna, where the sky is heavily light-polluted. Nonetheless, I image emission nebulae there, and do so using a set of 2" Baader CCD Narrowband Filters, which consists of a Hα, a [OIII] and a [SII] filter with band widths between 7 and 8.5 nanometers, in combination with the ATIK monochrome camera. Exposures of emission nebulae through all three filters can be combined to "Near Natural Color" or "Hubble Palette" color composits. I also own an older broad-band Hα filter with a band width of 35nm.

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DSLR Cameras

The Canon EOS 350D (=Digital Rebel XT) was my main astro camera before I bought my first CCD and is still in use as backup and as secondary camera for piggy-back photography of larger areas of the night sky using my assortment of Nikon lenses, many of them older fixed-focal-length lenses out of film days. I employ a Nikon Lens to Canon EOS Body Adapter to couple the Nikon lenses to the Canon 350D. The Canon 350D has a CMOS sensor with 3456 x 2304 effective pixels (8 megapixels) and a pixel size of 6.4μm x 6.4μm. To overcome the camera's weak Hα sensitivity, I have myself exchanged the original IR-cut filter by a Baader UV/IR cutoff filter, which was not an easy task, since the process voids the manufacturer's warranty and the risks of damaging the delicate parts in the camera's interior are high.

When astro-imaging with the Canon EOS 350D, I use a sensitivity of ISO 800. 10-minute exposures will yield a nice Signal-to-Noise (S/N) ratio and a sky background level somewhere between 10% and 30% of saturation level, and this ISO setting turned out to yield the best S/N for faint object detail if the conditions are good.

For startrail photos on a fixed tripod, I use a Nikon D7000, which I also employ for daytime imaging. It has not been modified. On the tripod, it is used with Nikon lenses, most often the Nikon 18-200mm VR lens. This is also the setup I use for time-lapse videos of the night sky, with the focal length locked to 18mm. For those, I use very high ISO settings of 3200 and above.

The bit depth of both cameras is 12 bits per color channel in RAW mode. Both cameras can work in several color spaces, originally I prefered Adobe RGB, more recently I switched to sRGB.

Lots of older DSLR images which can still be found in my webpages were taken with a Nikon D70 camera, where I also had replaced the IR-cut filter, and which was my first DSLR, bought in 2004. Before that, I was astro-imaging with a Nikon F3 film camera.

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Focusing the CCDs and the DSLRs is done manually on a not-too-bright and not-too-faint star within the frame. I do not have a focus motor on my scopes. Most often I use a Notebook and appropriate software for evaluating the star's "sharpness". Any software which provides the ability to repeatedly download subframes around a star and offers a zoom tool will do. An alternative method I use at times for focusing the DSLR cameras employs the camera's LCD screens, with Live View.

For the Nikon lenses, I have predetermined their exact focus spot by taking a test series of startrail images. For the zoom lenses, I have done that at several focal lengths. A microscale fixed on the focus ring of each lens provides reference.

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Exposure Times

When I have dark skies, the deep-sky exposure times are usually standardized to 10 minutes for individual exposures, with both CCDs and the Canon 350D. For those exceptionally darks skies which I sometimes encounter at remote sites, or when imaging through narrow-band filters, I recently started taking 20-minute exposures.

To minimize noise in the final image I take as many indivdual exposures of each object as I can. A series should at least include 12 exposures, although I had to work with less a few times.

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Since 2012 I am guiding my astrophotos with a Lacerta MGEN stand-alone autoguider. This is another one of these superb devices which worked perfectly right from the start and never gave me any problems. The MGEN is placed in the prime focus of a TS-Optics 8x50 Finder and works perfectly for all my telescopes. My prefered guider settings are: Mode 2, 0.3 pixel tolerance for both axis, and an agressiveness of 60%-120% depending on the seeing.

Previously, I guided my astrophotos with a Meade Pictor 216XT, which had just a 2-digit numerical display at its back, but could also guide stand-alone.

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Image Calibration

For both CCDs and the Canon camera, I take calibration frames: Dark frames and bias frames. Additionally, I take flatfields to correct for uneven illumination caused by the optics. To obtain flatfields I use an Aurora Flatfield Panel with a diameter of 220 mm set directly in front of the optics using the same setup, camera orientation and focus position as in the field.

I do not waste precious dark time under a clear sky for calibration exposures. Only the dark frames for the Canon camera (which have to be taken at the same ambient temperature as the light frames) are taken in the field, and that usually during packing.

For the startrail and still photographs taken with the Nikon camera, I take the simpler approach of using the automatic dark frame subtraction to subtract the so-called "amp glow" (actually it is not caused by heat, but by electroluminosity, the same thing you encounter in LEDs) in the upper left corner of the frame, and the dark current. Edge vignetting is corrected with the "Lens Correction" filter of Abobe Photoshop.

Currently, I do not use a special color calibration. Both DSLR cameras are set to the "full sun" white balance, that yields realistic color results.

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Image Processing

Basic data reduction (bias and dark frame subtraction, hot pixel filtering and flatfielding) for digital deep-sky images is done with IRIS, an excellent freeware image processing software written by Christian Buil. For stacking the many different images, I use the DeepSkyStacker. Further image processing is done in Adobe Photoshop, for noise filtering SGBNR is additionally employed. Getting the most out of astrophotos is a sophisticated process which takes a long time to learn. Jerry Lodriguss' Articles on Digital Techniques are an excellent starting point. Maybe I will publish some articles on my own digital processing techniques in the future (if I get enough requests from you :-)). The usual processing steps are: Basic data reduction, image combination, background flattening, logarithmic curves, color correction, local contrast enhancement, noise filtering, star size reduction, and final framing.

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Planetary Images

Images of planets, the sun and the moon were taken using the 9.5" Newtonian. Since the spring of 2010 I use an Imaging Source DBK 31AU03.AS single-shot color camera for planetary imaging, which features 1024 x 768 pixels and can be run at 30 frames per second (fps). A Televue 5x Powermate boosts the effective focal length of the telescope to about 6 meters for small planets. Older planetary images were taken with Philips PCVC 740K and 840K webcams.

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To read more about my telescopes, see my page about Telescopes and Equipment.

You want to start in astrophotography yourself? Or you want to improve your astrophotography techniques? Read the well-written Astrophotography Articles by Jerry Lodriguss. Again many thanks to him for his comprehensive descriptions, which where a lot of help to me, too!

There are many more images waiting to be processed, and many more beautiful objects waiting out there to be photographed, so this photo/CCD gallery will regularly be expanded with new images. So it may even be worth visiting it again... ;-)

© 2018 Dipl.-Ing. Dr. Walter Koprolin

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