Comet Catalina was a comet that was discovered in 2013, but only visible in the northern hemisphere in the autumn of 2015 and then into 2016 as it swung away from the sun. It was not very bright, and light pollution made it difficult for me to photograph it when it passed through an interesting area of sky in the Plough early on 16 January 2016.
The main image combines the stars and comet (processed separately so neither is blurred) from the same set of 92 images, each 30 seconds at ISO 800. In the picture, Mizar is top left, Alkaid top right, M101 at the bottom and the comet is half way between Alkaid and M101. This comprises 92 exposures stacked in DSS, once tracking the stars and once tracking the comet. The images of the background and the comet were then combined.
Comet Catalina, with Mizar, Alkaid and the galaxy M101
This smaller image is the comet with the blurred background unadjusted, giving the most accurate picture of the two tails, a long thin one and a much shorter 'fat and fuzzy' one. The picture shows how far the comet moved over a period of exactly an hour and a quarter.