Image processing techniques for gas morphology studies in the coma of comet Halley

1 – Image Enhancemen

A world map painted by Henricus Martellus c 1491 is widely acknowledged to be of great importance in the history of cartography, but has been little studied since it came to the attention of scholars in 1959 because the pigments used to write the descriptive texts and place names has faded or flaked off of the surface Spectral images of this map collected in August 2014 have been processed by several statistical methods, allowing much of the text to be recovered The methods may be applied to other documents and for forensic applications

Rediscovering text in the Yale Martellus map

On the rotation of the IRAS-Araki-Alcock nucleus

Several digital image processing techniques were used to improve the visibility of details, fans and jets, in the inner coma of the comet IRAS-Araki-Alcock 1983 VII on the short CCD-exposures taken by R. E. Schild with the 61-cm telescope through three I, J, and F band filters, at the Whipple Observatory during the close approach from May 6 through May 12, 1983. About 140 CCD images with the pixel size of 0.73 give a resolution about 20 km, and selected CDD frames presented together with isophotes demonstrate the variation and interrelation of the coma morphology and the nucleus activities during the observing period. Results and processed images are compared with observations taken by other observers during the same period.

Near-nucleus imaging of comet IRAS-Araki-Alcock 1983H1

Finely detailed striae in astronomical images can be important in formulation of theory. Examples are studies of streamers in the solar corona and of dust tails in comets. In both instances, conventional observations fail to reveal much of the structural detail. Digital image processing has been used at Los Alamos Scientific Laboratory (LASL) for enhancing these images. The corona images have tremendous variations in film density which must be eliminated before fine striae can be seen. These variations can be removed by means of numerical modeling of their spatial relation to the sun. This model can be thought of as a surface of background film density. In the comet images the overall variation is less severe. Further, the large number of comet images makes it infeasible to model them individually. Hence, an extreme low-pass filter was used to create an image which can be used as the background surface. In both cases, the background surface is divided into the original image pixel by pixel. This quotient image is then frequency-filtered for edge enhancement or noise control. Nonlinear density transformations are then used to enhance contrast. For both types of images, heretofore unmeasurable details become readily visible for analysis.

Enhancement of Solar Corona and Comet Details

Finely detailed striae in astronomical images can be important in formulation of theory. Examples are studies of streamers in the solar corona and of dust tails in comets. In both instances, conventional observations fail to reveal much of the structural detail. Digital image processing has been used at LASL for enhancing these images. The corona images have tremendous variations in film density which must be eliminated before fine striae can be seen. These variations can be removed by means of numerical modeling of their spatial relation to the sun. This model can be thought of as a surface of background film density. In the comet images the overall variation is less severe. Further, the large number of comet images makes it infeasible to model them individually. Hence, an extreme low-pass filter was used to create an image which can be used as the background surface. In both cases, the background surface is divided into the original image pixel-by-pixel. This quotient image is then frequency filtered for edge enhancement or noise control. Nonlinear density transformations are then used to enhance contrast. For both types of images, heretofore unmeasurable details become readily visible for analysis.

J. A. Farrell

Papers

Enhancement of Solar Corona and Comet Details

Enhancement Of Solar Corona And Comet Details