IC 443 - Jellyfish/Medusa Nebula

Date: 30/03/08    Time: 2130hrs   Location: Sunningwell   Temperature: 9.5ºC  Relative Humidity: 66%

Camera: Nikon D80    Scope: William Optics Z66 Apo Doublet at prime focus   Filter: Astronomik Hα narrow-band   Mount: piggy-backed on Meade LX90 in equatorial mode  Exposures: 15 + 17 + 15 + 16 minutes  ISO: 1600   F ratio: 5.9   Guidance: Autoguided

This is my first picture to be displayed monochrome.  It represents 63 minutes cumulative exposure of Hα-filtered light from the region around the star Propus (Eta η Geminorum) which can be seen as the bright star to the right of centre of the photograph.  IC 443 is a supernova remnant of a massive star in our galaxy approximately 5000 light years away,  which exploded some 8000 years ago.  (Sources vary in this estimate between 3000 and 30,000 years ago - which is as close as saying "we don't know" as far as I'm concerned - although if the distance estimates are correct, it must be more than 5000 years ago since the light from it has reaches us already.)  This was a challenging object to image for a learning-amateur like myself.  The key to this is, I believe, long-exposures with good tracking and clean skies.  I used a hydrogen-alpha filter because of the main wavelength of radiation coming from this emission nebula interacting with surrounding molecular gas clouds, so this picture was originally completely red.  Black and white points were set using the levels command in Paint Shop Pro, (dark subtraction having been carried out by the Nikon NR function) with midtone enhancement in the curves command.  The picture was desaturated and cropped, also in PSP.

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