Iris Nebula

Target details

The Iris Nebula (NGC 7023, Caldwell 4) is a bright reflection nebula in Cepheus, about 1,300 light-years away and six light-years across. Strictly speaking, NGC 7023 is the star cluster inside it. The nebula doesn't glow itself: it shines at magnitude +6.8 by reflecting the light of the magnitude +7 star SAO 19158.

Capture details

Data captured 24 September, 2017.
47x 10 minute exposures at ISO400.

Equipment details

Skywatcher Quattro 200 CF
NEQ6 Pro
Canon 40d (IR Filter removed)
Skywatcher ST-80
QHY5L-II

Processing details

This image was processed in Pixinsight & Lightroom.
Calibration and Stacking in Pixinsight.
Dynamic Crop - To remove black edges & integration artifacts.
Dynamic Background Extraction - To remove gradients.
Canon Banding Reduction script - To remove horizontal lines. (In this image it wasn't as effective as usual)
Photometric Colour Calibration - To colour calibrate the image.
Deconvolution - To bring out some fine detail.
Multiscale Linear Transform - Noise reduction.
Histrogram Transformation - To stretch the image and bring out the data.
TVGDenoise - Noise Reduction.
Curves Transformation - To increase contrast, without mask.
Local Histogram Equialisation - To sharpen and increase detail in dust, without mask.
Multiscale Linear Transform - To sharpen and increase detail, without mask.
Curves Transformation - To enhance blue, using starless mask.
Dark Structure Enhance - To bring out some detail surrounding the nebula core.

Export as JPEG and import into Lightroom.
Enhance Contrast (+25)
Clip Whites (-25)
Clip Blacks (-25)
Blue Saturation (+50)
Luminance (+50)
Graduated Filter to remove green cast in top and bottom left. Exposure (-0.5)

Export final JPEG for upload.