Sh2-240-20090118-Ha Back to Index Page Previous Image Next Image
Imaging Date: 13th - 18 Jan 2009

Designations :
Sh 2-240, Simeis 147

Object Type :
Supernova Remnant

Description :
These are the intricate filaments of faint supernova remnant Simeis 147. Seen towards the constellation Taurus it covers nearly 3 degrees (6 full moons) on the sky corresponding to a width of 160 light-years at the stellar debris cloud's estimated distance of 3,000 light-years. It is one of the faintest objects in the sky, discovered using a 25" Schmidt camera in 1952 by G.A Shajn and V.E. Hase at the Crimean Astrophyical Observatory at Simeis (in the former U.S.S.R). It was also imaged independently at Palomar by the 48" "Samuel Oschin" Schmidt camera on red photographic plates at roughly the same time period.
This supernova remnant has an apparent age of about 100,000 years - meaning light from the massive stellar explosion first reached Earth 100,000 years ago - but this expanding remnant is not the only aftermath. The cosmic catastrophe also left behind a spinning neutron star or pulsar, all that remains of the original star's core.

Coordinates (J2000) :
RA: 05h39m06.0s Dec: +2800'00"

Constellation : Taurus

Integrated Magnitude : N/A

Size : 3.3 degrees

Equipment details :
ART11002 through Pentax SDHF-75, unguided

Exposure details :
Ha = 115 x 600s (19.2 hours) binned 2x2

I have always been impressed by images of this very faint nebula, so thought I would give capturing it a go.
From the outset, I knew it would require a lot of long exposures, but with my main scope out of action I had to use my 75mm aperture scope, imaging unguided. The small aperture meant even more exposures were needed, but with an automated setup it was mainly a case of waiting for good weather.
I was using my 7nm Ha filter, which does a reasonable job of cutting out the moonlight - this was imaged starting just after the full moon, not ideal, but that's when the good weather started.
Even after stacking over 19 hours of subs with the 7nm filter, the nebula was only 15 ADU brighter than the background, so processing was tricky and good calibration essential. I used 100 sky flat field images to give a good correction to allow me to push the processing as much as possible.