C/2017 T2 (Panstarrs), a circumpolar comet

A few hours of clear sky made imaging comet C/2017 T2 (Panstarrs) possible, the comet was discovered at 20^th magnitude in September 2017 when it was 9.3 au ( 1 au is about 93 million miles ) from the Sun, it is now 1.5 au from the Sun and at approximately 10th magnitude. it can be found in the constellation of Perseus, this makes it currently circumpolar, meaning it does not set from UK latitudes.

The comet can be seen to move againts the background stars over a series of exposures, this is how they are discovered – an image is taken, then another of the same patch of sky a few hours or days later – anything that seems to have moved position is either an asteroid or a comet, comets tend to have a fuzzy appearence to them, as they approach the sun they warm up and produce a coma.

I took a total of 20 x 3 minute exposures through a clear filter, only this time instead of guiding on a star, I guided on the comets bright nucleus itself, this stops any elongation of the comet due to exposure lenght, this gives an hour of image data, but when you add dithering between images this gives 75 minutes from first image to last. After processing the images twice, once for the stars and once for the comet, then combining the two images together to give this final image.

Some of the tail was lost in processing the final image, if you look at the animated image you can see faintly the extent of the tail towards the left of the picture. Hopefully ( weather permitting ) I’ll get another chance to image this as it gets brighter on nearing the Sun.