Most H-a images of the sun are captured with either a DSLR, webcam or a more specialised CCD video camera connected to a telescope or camera lens with the appropriate solar protection. This post looks at the process of taking the video from a Imaging Source DMK41 CCD camera and converting it into a single image using Registax and PixInsight.
After processing all of the images have had their levels adjusted to that the image is fully stretched with no midpoint adjustment and no image data clipped. It should be noted that the final images have not been produced to make them ‘pretty’ they are purely for the comparison of the wavelet/deconvolution options available. To improve the visual appearance of the final image a mid point adjustment and an unsharp mask is applied, as shown in the final image.
The original 30 second video (15fps) was captured with the DMK41 mounted to a PST Stage 1 modified Lyra Optic 4″ f/11 refractor, seeing conditions was no more than average with the sun very low over the surrounding rooftops.
The images below show various treatments applied to the single stacked FITS image produced by Registax v6 after alignment of the video frames.
This is the single stacked image straight from Registax v6. If you want to play with the original FITS file it can be downloaded here
The next three images show the stacked image with Registax v6 wavelets applied in 3 levels of aggression.
The next image shows the Registax v6 stacked image processed in PixInsight to remove the vignetting on the right hand side of the original image. The vignetting was removed by using the Dynamic Background Extraction (DBE) in PixInsight.
The image below is the DBE processed image with the PixInsight deconvolution function applied.
A levels mid point adjustment is now applied to lighten the image and a touch of unsharp mask to tighten up the edges.
Other adjustments could be made to visually improve the image like curves adjustment and colourising.