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IC 443
Supernova Remnant
aka SNR 189.1+03.0, Sh 2-248, LBN 844
Integrated Visual Magnitude: 12
Apparent Diameter: 50'

Minimum requirements to view: 8-inch scope, OIII filter and very dark skies

IC 433 is a supernova remnant that was once only visible in photographs and very large telescopes.  Specialized, narrow band filters, such as the UHC or OIII, have changed this.  With an OIII filter in place the brighter portions of this nebula are now within reach of experienced users of 8-inch or larger telescopes observing from a dark location.
A spectacular object in photographs, only the brightest regions are visible in the typical amateur telescope.
I first observed IC 443 in January 2001 with my 18-inch f/4.5 Dob.  I was only able to make out this nebula with the OIII in place, perhaps due to the unusually bright sky on that night.  At 94x I was able to see the brightest (southern) portion of the large arc, appearing a bit like a curved, 4-day old moon.
The field in an 18-inch at 94x (22mm Panoptic).  The bright star to the upper left is Eta Gem.  The brightest portion is the small, arc-shaped knot on the lower left.  North is down and east is to the right.
The supernova that created IC 443 probably occurred some 3000 years ago.  As the shock and debris from the explosion spread outward it met a nearby molecular cloud complex.  The interaction resulted in the filimentary structure we see in photographs.  A molecular cloud complex is a region of cold, high-density gas.  It is out of such cloud complexes that stars can form, sometimes triggered by the passing shock of a nearby supernova.    Interestingly, the remains of a much older supernova remnant (possibly as old as 100,000 years) can be seen in silhouette in x-ray images.

IC 443 in X-rays

Millennium Star Atlas Vol I Chart 156
Sky Atlas 2000 Chart 5
Uranometria 2000 Vol I Chart 137