Collecting  Photons

IC 1805 - Cassiopeia

This area is dominated by a large nebula powered by several loose open clusters which can be seen decorated by the lovely diffraction spikes. The field is about 1° 22' wide and, at the computed distance of the nebula (7500 LY) spans about 170 LY. The complex is far larger since it includes also the IC 1848 nebular cluster and several fainter nebular extensions to the north IC 1891. All this covers about 25 square degrees of sky, for a likely diameter of over 600 LY.

The image has been assembled by using two data set obtained with the ASA astrograph. The RGB data is comprised of 37x8' frames shot through an IDAS anti pollution filter. The Hα signal was imaged with 15x16' frames through a 6nm Astronomik filter. After registration, the Hα data was added to the red channel of the RGB composite. A small fraction of the overall Hα signal has been added to the B channel to account for the Hβ emission. Processing included hyperbolic asinh in Iris, gradient subtraction and several luminance masked operations on the transfer function (Pix Insight and CS). I have used photoshop CS for the composition and blending of the layers. I am not satisfied yet of the colour rendition, but for the time being this has to suffice. The Hydrogen image is less colourful, would require more integration but is more interesting:

The Hα image (17x16' subs; Astronomik, 6nm)

A shock front north of the nebula center. RA: 02h 35m 31 - Dec: +61° 50' 36"	The power house of the complex: the open cluster Melotte 15 dominated by three bright O-stars. The full resolution shows several pillars formed by radiation erosion. RA: 2h 33m 25s - Dec: +61° 30' 3"
A cometary protusion at the north side. RA: 2h 40m 00s - Dec: +61° 55' 28	Pillars eroded by Melotte 15: the protusions point toward the supergiant stars. RA: 2h 36m 45s - Dec: +61° 19' 30"

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