Important info:

• The Copyright and Reproduction Policy.
• Prints of Walter's astrophotos are available for purchase, see the Print Purchase Info.
• If you are interested in Walter's astrophotography setup and the equipment he uses, see About these images...
• Please calibrate your monitor to view my astrophotos as they are intended to be seen.
• If you want to contact Howdii or Walter, e-mail addresses are given below.

In this gallery, I (Walter Koprolin) present my best results in astrophotography, and also a few of Howdii's results. The images which can be found here were obtained using digital cameras, film cameras, webcams and CCDs dedicated for amateur astronomers.

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

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

Galaxies	Globular Clusters	Galactic Clusters
Galactic Nebulae	Supernova Remnants	Star Fields
Planetary Nebulae	Solar System	Comets
	Nightscape

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

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

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

Table of Contents:

• Telescopes
• Mounts
• Tripods
• CCDs
• Filters
• DSLR Cameras
• Focusing
• Exposure Times
• Guiding
• Image Calibration
• Image Processing
• Other CCD and Webcam Images
• Miscellaneous

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Telescopes

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

	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 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.
	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.
	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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Mounts

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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Tripods

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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Controllers

For photography, both mounts can be controlled by a PowerFlex MTS-3SDI, which features everything an astrophotographer 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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CCDs

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 bits. 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 other CCD is an ALccd 6c Pro, which is called QHY8 Pro in English-speaking countries. It features a Sony CCD sensor with 3032 x 2016 effective pixels (6 megapixels). Pixel size is 7.8μm x 7.8μm, bit depth is 16 bits. The QHY8 Pro is a one-shot color camera with an RGGB bayer matrix on the CCD. It can be cooled down to -45 degrees below ambient temperature, the chip temperature is regulated. While basically a good camera, and cheap as CCDs go, it has a few drawbacks, most annoying is its tendency to collect dew (and occasionally ice) on the CCD window and - additionally - on the chip once its temperature drops below 0°C. The QHY8 is used for taking color data of deep-sky objects, recently often for combination with luminance or Hα data obtained with the ATIK during image processing.

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Filters

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.

For startrail photos on a fixed tripod, I use a third camera, a Nikon D40, which I also employ for daytime imaging. It has not been modified. On the tripod, it is used with Nikon lenses, recently most often the Nikon 18-200mm VR lens. Since the spring of 2010, a fast Nikon 50mm f/1.4 lens employed fully open is used on the D40 to capture untrailed stars, sky background, and foreground objects all in one frame with short exposures (a few seconds) for nighttime environment documentation.

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 at his webpage 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

Focusing the CCDs and the Canon EOS 350D 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, although neither the 350D nor the D40 do offer Live View. However, a series of 1 second exposures taken during turning the focus knob and displayed a max magnification for critical examination works well enough, especially since you can quickly cycle through exposures by using the camera's thumbwheel.

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. With the Canon camera, 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 the ISO setting I use with the Canon camera turned out to yield the best S/N for faint object detail if the conditions are good.

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.

I am still experimenting with gain and offset values for the QHY8 Pro. A gain of 20% seems to work well for stars and 50% is the value I use for faint nebulae.

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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Guiding

As guidescope for all of my telescopes a parallel-mounted 63/840 Zeiss Telementor2 achromatic refractor (1986 version) is used. This already is a good scope on its own which delivers excellent stellar images for the autoguider, but is a bit on the heavy side for a guidescope. I use it together with a 2x Barlow lens to boost the effective focal length for the autoguider, and with a flip-mirror system to search and center the guidestar using an illuminated crosshair eyepiece.

My autoguider is a Meade Pictor 216XT which is quite obsolete these days. While its operation is a bit awkward and takes getting used to, and it does not feature sub-pixel guiding, it does fine for my long focal length guidescope, most images guided by the Pictor show circular stars and no trailing (although some do, but I'm not sure whether the Pictor is to blame). If you understand German, you can read my old report on the Pictor 216 XT. I prefer it because it is a stand-alone autoguider, it does not require a computer, control box or separate software for guiding.

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Image Calibration

For both the CCD 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 with the smaller optics, I simply use my LCD computer monitor at home, set to pure white, and photograph it using the same setup, camera orientation and focus position as in the field. For the 9.5" Newtonian, the LCD screen is too small, so I use the rough-textured and reasonably evenly illuminated white ceiling of my living room at home for "ceiling flats".

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. The QHY8 Pro gets a simple red:green:blue scaling of 1:1:1 during color conversion, which works well for most cases.

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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. 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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Other CCD and Planetary Images

Some CCD images which can be found in these pages were obtained by my observing partner Wolfgang "Howdii" Howurek. He uses a ST-8XME camera for monochrome and a ST-402 camera for color imaging, both are produced by SBIG in California. Most often, these CCDs are used on Howdii's Intes-Micro 8" f/6 Maksutov-Newton or his APM 4" f/8 APO refractor, which are now both mounted side-by-side on a heavy-duty AOK WAM 450 mount at his O2O observatory.

Images of planets, the sun and the moon are for the greater part taken by Howdii at his observatory with the 8" Maksotov-Newtonian. My own planetary images are taken using the 9.5" Newtonian. Since the spring of 2010 we both 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), although my notebook only manages 15 fps at download via USB. A Televue 5x Powermate boosts the effective focal length of both our telescopes for small planets. Older planetary images were taken with Philips PCVC 740K and 840K webcams.

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Miscellaneous

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

The astronomical descriptions of individual objects found in the gallery were written by me, the observing hints by my experienced observing partner Wolfgang "Howdii" Howurek, I did only translate them into English. Many thanks to him!

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 photos waiting at home to be scanned, 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... ;-)

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