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Contains:  NGC 4236, NGC 4120
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NGC 4236, 





    
        

            Jonathan W MacCollum
NGC 4236

NGC 4236

Technical card

Imaging telescope or lens:Orion 203/1000 f/4.9

Imaging camera:ZWO ASI071MC Pro

Mount:Celestron CGEM

Guiding telescope or lens:ZWO OAG

Guiding camera:ZWO ASI 178MM

Software:PixInsight PinInsight 1.8.5Isbeorn N.I.N.A.PHD 2

Filter:Hutech IDAS LPS D1 2"

Accessory:Skywatcher 2" Coma Corrector f/4

Resolution: 8545x4796

Dates:March 6, 2019March 11, 2019March 28, 2019

Frames:
398x120" -10C
390x60" -10C

Integration: 19.8 hours

Darks: ~60

Flats: ~30

Flat darks: ~30

Avg. Moon age: 18.76 days

Avg. Moon phase: 22.68%

Bortle Dark-Sky Scale: 4.00

Astrometry.net job: 2653519

RA center: 183.387 degrees

DEC center: 69.439 degrees

Pixel scale: 0.492 arcsec/pixel

Orientation: 187.729 degrees

Field radius: 0.670 degrees

Data source: Backyard

Description

**NGC 4236**

**Equipment:**

* Orion 8in f4.9 1000mm / Flocked / Mask on Turned down edge on primary

* Guiding with ZWO OAG and asi178mm camera

* ASI071mc one-shot-color cam

* Hutech IDAS LPS D1 Filter

* Celestron CGEM Mount

**Acquisition:**

* Lights:
163x120.0s at -10C on 2019-03-06
235x120.0s at -10C on 2019-03-11
003x120.0s at -10C on 2019-03-28
390x060.0s at -10C on 2019-03-28

* Flats: combination of sky flats and ceiling flats for each session

* Darks: 60x60s at -10C

* Darks: 60x120s at -10C

* Bias: None

* Bortle Dark-Sky Scale: 4.00

* Pixel scale: 0.981 arcsec/pixel / 2x (from drizzle)

* Orientation: 187 degrees

**Pre-Processing with PixInsight:**

* Calibrated and stacked using [LVA PreProcessing Steps](http://www.lightvortexastronomy.com/tutorial-pre-processing-calibrating-and-stacking-images-in-pixinsight.html)

* Integrated best 751 of 792 frames selected using a combination of Blink Subframe Selector

* Weighting:
```
10*(1-(FWHM - FWHMMin) / (FWHMMax - FWHMMin))
+ 45*(1-(Eccentricity - EccentricityMin) / (EccentricityMax - EccentricityMin))
+ 35*((SNRWeight - SNRWeightMin) / (SNRWeightMax - SNRWeightMin))
+ 30
```

Processing Steps:
I've decided my processing workflow can be best summarized with pseudocode:

```F#

/// Pre Processing
let rgb =
Image Integration
|> Drizzle Integration (CFA, Scale 2.0, Drop Shrink 0.7)
|> Dynamic Crop
|> Dynamic Background Extraction
|> Background Neutralization <| (4 Previews |> Preview Aggregator)
|> Color Calibration
|> Image Solver
|> Photometric Color Calibration
|> RGB Working Space <| (1,1,1)

/// Synthetic Luminance
let l_orig =
rgb
|> extract synthetic luminance

/// Background Noise Reduction
let l_nr =
l_orig
|> Tgvnr // Small Scale Noise Reduction
|> Mmtnr // Large Scale Noise Reduction

/// High-Signal Sharpening
let l_sharpen =
l_orig
|> Deconvolution // 5-layer regularization no deringinging
|> Replace stars <| star mask <| l_orig
|> Mmt sharpen

/// Prepare mask for combining Low-Signal background with High Signal Foreground
let l_combine_mask =
l_nr
|> stf
|> hist stretch cliping whites and blacks
|> blur

/// Combine Low-Signal background with High Signal Foreground
let l =
l_orig
|> l_nr (inverted l_combine_mask)
|> l_sharpen (l_combine_mask)
|> Histogram Transformation // Stretch to non-linear
|> Local Histogram Equalization <|
mask((l_combine_mask-star_mask)|>convolution))

/// RGB cleanup and combination
let final =
rgb
|> tgvnr
|> mmtnr
|> shrink stars
|> histogram transfromation
|> lrgb combination(l)
|> curves to boost contrast and saturation
|> cleanup artifacts in brighter stars

```

* Save as JPEG

Comments

Author

eigenVector
Jonathan W MacCollum
License: Attribution-NoDerivs Creative Commons
932
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NGC 4236, 





    
        

            Jonathan W MacCollum

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