At the start of the year, Comet 144P Kushida had just glided eastwards from Aries into Taurus. At magnitude 10.7 and no discernible tail, it glows eerily to the north west of the mag 7.4 star GSC 1234-545, which by comparisonshines brightly towards the bottom of the picture.



This picture 'freezes' the motion of the comet against the background stars by using some image processing trickery. First of all I used AstroArt to stack the images in AstroArt so as to correlate the stars, which results in sharp background stars and a trailed comet image. I then repeat the stacking process, this time to use the comet as the correlation reference point, which results in a good comet image with blurred background stars.

The second phase uses Adobe Photoshop: I created a layer with the crisp background stars and erased the trailed comet (using the healing brush and clone stamp tool). I then added a second layer using the image of the comet and trailed stars. After aligning the two layers, I used a layer mask on the second layer to hide everything on that layer. By then erasing the mask around the comet I could allow the image of the comet to show through against the background of field stars. A little Gaussian blur of the mask allows a smooth blending of the comet onto its background with the result you see above.