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Digital Image Processing for Comets

Starting into the field of astronomical image processing is a long and time-consuming learning process, especially without guidance.
Buying the wrong software or equipment can get expensive and frustrating.

Especially for beginners
, reading this "book" provides an easier entry into comet photography. For all other beginners in astrophotography it teachs the basics of astronomical image processing, explains the CCD technology, provides an overview of CCD cameras, producers and distributors, as well as the practical doing with attractively priced commercial software, but also with freeware.

The first edition was free for individuals. It was possible to make a donation for this publication.


I observe and image comets since 1987. I started with a SLR on a mobile tracking platform owned by a friend. After acquiring a equatorial mount and a 13cm Newtonian I imaged the first comets through a telescope. The next step was the use of self hypersensitized Kodak Technical Pan 2415 film. With a 15cm Newtonian and a 5.5-inch Schmidt camera from Celestron I made observations in the South of France and in Namibia. A 20cm Newton, a CCD camera and a unmodified digital SLR were used for several years.

Until 2003 I observed comets visually and made brightness estimations. But after the acquisition of a CCD camera I observe only the brighter comets visually.

Some visual observations, however, have left a long lasting impression. Among them are, for example, the visual observation of a "bright" 13 mag. comet with the 1-meter telescope of Dany Cardoen in Puimichel, Southern France, the dust bowls of C/1995O1 Hale-Bopp, an of course the show of C/1996B2 Hyakutake in March 1996.

However, it is important to me to have portable equipment to observe comets outside the cities. Therefore, the telescope must not be too large.

A view pages of the second editon can be downloaded at the bottom. (12.03.2016 link fixed)

The copyright is owned by Stefan Beck.

I welcome your feedback, criticism and requests.

Stefan Beck

Email: (

Table of Contents
1. Introduction
1.1 Equipment for imaging comets
2. Basics to CCD / CMOS image sensors
2.1 Full-Frame / Interline CCD sensor
2.2 Microlenses
2.3 Number of pixels
2.4 Pixel size
2.5 Surface
2.6 Characteristics of the image sensors
2.7 Cooling
2.8 Electronics
2.9 Field of application
2.10 Resolution
3. Basic concepts + practices
3.1 Light or Light frame
3.2 Dark or Dark frame
3.3 Bias or Bias frame
3.4 Flat or Flat frame
3.5 Creating a Flat frame
3.6 Creating a Dark frame
3.7 Creating a Bias frame
4. Standard image processing and calibration
4.1. Calibration of the data
4.2. Calibration with Astroart, how to do it
4.2.1 Manual calibration
4.2.2 Batch processing with Astroart including stacking the calibrated images
4.3 Calibration with Fitswork. How to do it.
4.3.1 Creating Master dark-/Master flats
4.3.2 Manual method of calibrating images
4.3.3 Automatic method, stacking of calibrated images
4.4 Processing RAW-Images of DLSR cameras
4.4.1 Developing a RAW Image with Fitswork
4.4.2 Batch mode RAW Images
5. Advanced image processing
5.1 Histogram
5.2 Levels
5.3 Curves
5.4 Digital Development Processing
5.5 Noise reduction + sharpening + save as JPG
6. Special processing of comet images
6.1 Stacking without star trails
6.2 DeepSkyStacker-Method
6.3. Radial Weighted Model + Median Coma Model with Astroart
6.4 Larson-Sekanina filter
6.4.1 Exampel: How to use the Larson-Sekanina filter
6.4.2 Example with Astroart
6.4.3 Example with Fitswork
6.4.4 Example with positive display, jet- and tail structures
6.4.5 How to remove the double stars within Larson-Sekanina filtered images
7. Tools
7.1 Measuring the tail and coma with Astrometrica
7.2 Orbitas, caculating the maximum exposure time
7.2.1 Configuration
7.3 Imageprocessing with Imagemagick
8. Evaluation, documentation and publication
9. Table of CCD cameras, manufacturers, software

91 pages with many screenshots.

Some pages of the content to download.

The price is 7,99 Euro.

You will receive the PDF (7 MB) via email. There is no automatic processing. Therefore it can take some days until your receive the document. Just send me an email if you have questions.

Download some raw images ( 3 images, 1 flat, 1 master dark ) to try the standard image processing.

1. Publication: December 2015