Target Details
The Iris Nebula, also NGC 7023 and Caldwell 4, is a bright reflection nebula and Caldwell object in the constellation Cepheus. NGC 7023 is actually the cluster within the nebula,the nebula is lit by a magnitude +7 star, SAO 19158. It shines at magnitude +6.8, it lies 1,300 light-years away and is six light-years across.

Capture Details
Data captured 16 sessions between 21 April & 18 May, 2018.

82x 2 minute exposures with Red filter (Binned 2x2)
81x 2 minute exposures with Green filter (Binned 2x2)
80x 2 minute exposures with Blue filter (Binned 2x2)
230x 3 minute exposures with Luminance filter.

Total Exposure: 19.6 hours.

Equipment Details
Skywatcher Quattro 200 CF
NEQ6 Pro
Atik 428EX Mono
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. (All channels separately)
Dynamic Background Extraction - To remove gradients. (All channels separately)
Deconvolution - To bring out some fine detail (Luminance only).
Multiscale Linear Transform - Noise reduction (All channels).
Linear fit - to align brightness of RGB, red as reference.
Channel Combination - to create RGB image
Photometric Colour Calibration - To colour calibrate the RGB image.
SCNR - To neutralise Green. (RGB image)
Channel Extraction - To split R,G & B.
Histogram Transformation - To stretch Lum, R, G & B separately, using preview with statistics module to get same background level.
Multiscale Median Transform - To extract Large Scale structures from Luminance Image.
Pixelmath - To extract Small scale structures (Original minus Large Scale)
Histogram Transformation - Small stretch to highlight dust, range mask in place to protect nebula core. (Large Scale only)
Local Histogram Equalistion - To boost contrast of dust, previous mask in place. (Large Scale only)
Curves - To boost dust, previous mask in place. (Large Scale only)
ATrous Wavelet Transform - To boost small scale dust. (Small Scale only)
Histogram Transformation - To bring up small scale dust. (Small Scale only)
Pixelmath - Recombine Large & Small scale images.
LRGB Combination - To create LRGB image.
HDR Multiscale Transform - To recover detail in bright core, rangemask in place to select core only.
Pixelmath - To blend HDR image with original, 50-50.
UnsharpMask - To sharpen detail in core, with sharpening mask in place.
Histogram Transformation - To brighten image slightly.
Curves Transformation - To Desaturate backgorund, with mask to protect nebula and stars
Curves Transformation - To Boost star saturation, with inverted starmask in place.
Histogram Transformation - To bright image and expose dust further.
Curves Transformation - To reduce purple colour cast in one corner, with stretched magenta mask in place.
Histogram Transformation - To brighten image slightly.

Export as JPEG and import into Lightroom.
Enhance Contrast (+25)
Clip Blacks Slightly (-10)
Aqua Saturation Boost (+25)
Blue Saturation Boost (+50)

Export final JPEG for upload