The Helix Nebula, NGC7293 in Aquarius.
This image is a stack of 8 sixteen minute exposures shot through a Hydrogen-alpha filter,
combined with red, green and blue filtered exposures integrated for 40 minutes each.
The H-alpha image used for the luminance channels is shown in the image below.
The exposures were acquired using an SXV-H9 CCD camera on a Tele Vue NP-101 4" f/5.4 refractor.
The exposures were calibrated, defect-corrected and stacked using AIP4WIN.
They were automatically G2V-balanced and combined using AIP4Win's automated color tools.
This image has been resampled down from its original size of 1392x1040.