IC 1318
Sky-Watcher Esprit 70 EDX First Light

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July 5, 2025

IC 1318 is the nebula around the bright star gamma-Cygni at upper left in this photo. Gamma-Cyg is the star where the body and wings of Cygnus, the swan, cross in the sky.  Cygnus is a rich region for imaging during summer and fall in the Northern Hemisphere. Despite its appearance in this image, this nebula is actually faint and tenuous visually — the brightest parts are visible in a dark sky with a big telescope, but they look just like a faint haze in the eyepiece. The brightness of gamma-Cygni makes it challenging to see faint objects unless you keep the bright star out of the eyepiece field of view. I framed this image to also capture the Crescent Nebula, NGC 6888, at lower right.

This is the First Light Image for a new telescope:  the Sky-Watcher Esprit 70 EDX. Unlike the Esprit 80mm, this scope has an image circle that can cover a full-frame 35mm sensor with pinpoint stars. The field of view is a whopping 4.5 x 3 degrees. Focus was stable over a 3C temperature range (I focused only once, manually, at the start of a 4-hour imaging run). They will hopefully be available to buy later in 2025.

Tekkies:
Acquisition, focusing, and control of Paramount MX mount and other equipment with N.I.N.A. and TheSkyX. Unguided, manual focus. Equipment control with Primalucelab Eagle 4 Pro computer. All pre-processing and processing in PixInsight. Acquired from my SkyShed in Guelph. Acquired under average transparency and seeing and a first-quarter Moon on the night of July 4-5, 2025.

First Light with Sky-Watcher Esprit 70 EDX refractor. QHY367C Pro camera with Optolong L-Quad Enhance filter.

41 x 5m = 3hr 25m

Image scale 1.1 arcsec per pixel (with 2X Drizzle)

 
Finder Chart and Annotated Image:
 
 
 
Data Reduction and Linear Processing

Preprocessing: The WeightedBatchPreProcessing script was used to perform calibration, cosmetic correction, debayering, weighting, registration, integration and Drizzle integration of all frames (2x drizzle, 1.0 Drop Shrink).

Gradient Removal: Graxpert was applied with default settings except smoothing = 0.5.

Colour Calibration: BlurXterminator was applied to the RGB master with Correct Only selected, followed by SpectrophotometricColorCalibration.

Deconvolution: BlurXterminator was applied to the RGB master with Automatic psf , star sharpening set to 0.5, and non-stellar set to 0.9. 

Linear Noise Reduction: NoiseXterminator was applied with settings Amount=0.9 and Iterations=4.

Stretching:  HistogramTransformation was applied to make a pleasing image with background approximately 0.08. 

Nonlinear Processing

Star Removal:  StarXterminator was used to remove the stars from the master, with default settings, except Large Overlap was selected. The stars-only image was retained.

Nonlinear Noise Reduction: NoiseXterminator was applied with Amount=0.9 and Iterations = 4

Re-stretch: HistogramTransformation was used to boost contrast by moving the dark point to the toe of the histogram and slightly decreasing the mid-point slider.

Contrast Enhancement: LocalHistogramEqualization was applied twice. A Contrast Limit of 1.5 and 1 iteration was used for each LHE application (scale 50, strength 0.25; scale 320, strength 0.18).

Sharpening: MultiscaleMedianTransform was applied. (Layers 2 – 4 with strengths of 0.03 0.04, and 0.02 respectively).

Contrast, Brightness and Colour: Brightness, contrast, hue, and saturation were adjusted in several iterations using CurvesTransformation and the Jurgen Terpe Selective Color Correction script, with masks as required.

Stars-only steps: The CIE L* channel (i.e. the lightness channel) was extracted from the stars-only image and then applied to the star image as a mask. CurvesTransformation’s Saturation slider was used to boost colour in the stars.

Star Restoration: The PixelMath expression combine(starless, stars, op_screen())  was used to combine the starless starless image with the stars-only image. The StarReduction script was applied with small star protection enabled (Tranfer method, strength 0.4) to slightly reduce the larger stars.

Final Steps: Background, galaxy, and star brightness, contrast, and saturation were adjusted in several iterations using CurvesTransformation with masks as required. ICCProfileTransformation (sRGB IEC61966-2.1; Relative Colorimetric with black point compensation) was applied prior to saving as a jpg. The finder chart was made using the FindingChart process. The annotated image was made with the AnnotateImage script.