Strangers in the Night – Comet 103P passes by the Pacman Nebula


Nick Howes

Cherhill, Wilsthire

TMB105 F6.2 telescope on an EQMOD/EQ Mosaic controlled EQ6 mount. Atik 4000 mono CCD, Astronomik CLS/HA/OIII and SII filters

Image which took several weeks to compile.edit and tweak. Initial run using an Atik 314L camera and narrowband CCD filters (Astronomik HA/OIII/SII and CLS) imaged the comet in the field of NGC281, using a multi pane wireframe approach (taking just a few subs for each of the 4 areas including the starfield/NGC281).

Then the comet was imaged in full on the night of closest approach to NGC281, with 30-60s sub frames in HA/OIII/SII narrowband augmented by a CLS filter. where the OIII channel really lit up quite well.

Then using a median combine method to eliminate the starfields, and then a SD combine on the starfield to put the comet back in to its correct position with no trailing (method used on other images I have made just of the comet), the comet was placed back into the correct FOV area against NGC281. The framework of star reference points and the nebula were imaged on the same night (one-two subs for each, relatively short) using the CLS filter and a H-A filter for the Nebula basic outline/shell.

Then gradually over several weeks, data was gathered to get enough sub frame time on the nebula in narrowband, mapping to a combination pallette of HST mapping and HA/OIII/SII, (total integration time around 12 hours in 300s sub frames), and the surrounding starfields. As the comet was moving very quickly, this was the only way it could be done to achieve this level of detail and complexity in the final image.

Atik 314L and Atik 4000CCD
Manually composited, along with use of Registar/MAxim DL/Photoshop CS5
TMB105 F6.2 refractor
Autoguided by PHD guide/ST102
EQ6 mount using EQ MOD and EQ Mosaic for the initial wireframe
Processed in Maxim DL/Registar and Photoshop CS5 using Noels Actions and Focus Magic plug in/DDP processing in MAxim DL for Nebula, Deconvolution FT process on star fields and nebula in Maxim DL.

Taken in Oct 2010 from my home in Cherhill, WIltshire, UK, this comet has since gone on to show quite remarkable activity compared to any other, with abundant CO2 being the most unusual ever seen from a cometary body.