JWST NIRCam starless and luminance approach for postprocessing

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NGC2070 Tarantula Nebula in Dorado, JWST NIRCAM raw data

After processing James Webb Space Telescope raw calibrated .fit data focused about NGC2070 by Photoshop screen colorized blending layers, with colours assigned according to NIRCAM filters guideline (cfr.: https://jwst-docs.stsci.edu/jwst-near-infrared-camera ) I was able to obtain this preliminary result.

Integration of NIRCAM f090W, f187N, f200W, f335M and f444W filters

According to spectrum values indicated by NIRCAM filters guidelines I decided a different approach for postproduction, considering the lowest nm values as “blue” colour band, the middle nm values as green, and the highest nm as red channel for an RGB combination.

Using Pixelmath I thus combined in PixInSight f090W and f187N masters creating my blue channel, f200W and f335N as the green channel, and f444W master for red channel.

NIRCAM f090W + f187N filter integration (PixInSight > Pixelmath)
NIRCAM f200W + f335N filter integration (PixInSight > Pixelmath)
NIRCAM f444W filter

Being NIRCAM data results of very narrowband recordings, I approach such masters as a peculiar SHO integration, and decided to attempt a starless integration for nebula details and colours work, and final recomposition of starry image using star luminance layer.

Starless version of each master I obtained by PixInSight > Starnet2. Each master I then stretched and export as .tiff in Photoshop for contrast adjustement, star residual removing and hot pixels fixing.

Starless NIRCAM f090W + f187N filter integration
Starless NIRCAM f200W + f335N filter integration
Starless NIRCAM f444W filter

In Photoshop I imported each master into pertinent RGB channel. Then I provide to contrast, saturation and Brightness adjustement layers and fix other pixels problem emerged from channels combination.

Starless LRGB integration where: L=f444W R=f444W G=f200W+f335N B=f090W+f187M JWST NIRCAM NGC2070

Starry NIRCAM f444W filter master as luminance was finally imported as upper layer in luminosity blending mode, while starless f444W master for starless version.

JWST NIRCam NGC2070 Tarantula Nebula

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James Webb Space Telescope NIRCam NGC2070 “Tarantula Nebula” , filters f090W, f187N, f200W, f335M and f444W

Photoshop screen blending mode and colorizing layers of f090W, f187N, f200W, f335M, f444W master calibrated RAW .fit data of James Webb Space Telescope NIRCAM mosaic photo session focused on NGC 2070.

Astrobin: https://www.astrobin.com/uv9q6w/

NGC1365, approaching to JWST MIRI data

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NGC 1365 JWST MIRI mosaic, filters f770W, f1000W, f1130W and f2100W

According to James Webb Space Telescope official documentation (cfr. https://jwst-docs.stsci.edu/jwst-mid-infrared-instrument) the JWST Mid-Infrared Instrument (MIRI) provides imaging and spectroscopic observing modes from 4.9 to 27.9 μm. These wavelengths can be utilized for studies including, but not limited to: direct imaging of young warm exoplanets and spectroscopy of their atmospheres; identification and characterization of the first galaxies at redshifts z > 7; and analysis of warm dust and molecular gas in young stars and proto-planetary disks.

MIRI imaging filter curves and wavelenght are resumed below

MIRI imaging filter curves – https://jwst-docs.stsci.edu/jwst-mid-infrared-instrument, figure 3

MIRI coronagraphic imaging filter curves – https://jwst-docs.stsci.edu/jwst-mid-infrared-instrument, figure 4

From Mikulksky Archive for Space Telescopes I downloaded raw calibrated .tif data focused about NGC 1365 Great Barred Spiral Galaxy, a double-barred spiral galaxy about 56 million light-years away in the constellation Fornax.

Among all data available I picked-up 3 sessions: a wide field MIRI mosaic by filters f770W, f1000W, f1130W and f2100W, a small field MIRI mosaic by the same filters f770W, f1000W, f1130W and f2100W a small NIRCAM field mosaic by filters f200W, f300M, f335M and f360M.

NGC 1365 JWST MIRI mosaic, filters f770W, f1000W, f1130W and f2100W
NGC 1365 JWST NIRCAM mosaic, filters f200W, f300M, f335M, f360M

NGC 3324: approaching JWST raw data (.fits) for post-production attempt

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After and according to Warren Keller intro and divulgation paper focused about James Webb Space Telescope raw data availability from MAST Portal, archive named after Barbara Mikulski fulls of tons and tons of data including Hubble Space Telescope’s .fits calibrated frames, I’ve downloaded a couple of sets focused on NGC 3132 and NGC 3324 to begin an attempt of post-processing.

Browsing mast portal is kinda experience within a state of art information retrieval system: filters options permits to produce precise queries for matching desired set of data. 

JWST target session produce .zip archives tagged, among other criteria, by NIRCAM, MIRI and NIRSPEC instrument label. 

According to JWST user documentation

https://jwst-docs.stsci.edu/jwst-observatory-hardware [10/02/2023]

with hardware specifications, and as according to Warren Keller 

https://www.skyatnightmagazine.com/astrophotography/astrophoto-tips/produce-images-using-james-webb-space-telescope-data/ [15/02/2023]

and Nico Carver 

https://youtu.be/DVuonz26P0w [15/02/2023]

suggestions and guidelines about JWST raw data elaboration and post production, most convenient and useful data for an Astrophotographic approach come from NIRCAM sensors and filters. 

NIR camera JWST official documentation guidelines specifies and classifies the following filters wheels clusters:

and resumes microns wavelength of filters set as pictured below :

Cfr: https://jwst-docs.stsci.edu/jwst-near-infrared-camera

and cfr KWST user documentation 


Wavelength and filters label specification, assigned to visible spectrum compass, as confirmed by Keller and Carver tributes, suggests and permits two approach as attempt of post-production and elaboration of JWST NIRCam available data:

  1. a “simplified” RGB or LRGB image integration by channel combination
  2. a “more complex” image integration by available channel combination

An RGB or LRGB approach is “simple” as it consists essentially in identifying proper NIRCAM filter most representative data for RGB channels and integrate them by simple melting channel combination in – for instance – PixInSight: Process > Channel Management > Combination.

NGC 3324 NIRCAM filters available data are f090W, f187N, f200W, f335M, f444W and MIRI f770W, f1130W, f1280W, f1800W. 

MAST portal retrieved data for NGC3324 filter by JWST mission

Letting MIRI data to further investigation, I focused on NIRCAM range records download them all.

Each .zip archives exploded out as follow:

file of interest is the _i2d.fits file, generally speaking the biggest among all records.

Opening it in PixInSight generate 8 preview:

A quick autostretch easily let us identify the proper image which I always found as the first, thus the downer pop-up opened.

In the name of .fits file are indicated which filter belongs to, thus it’s very easy to select.

Among JWST data from NIRCAM records focus about NGC 3324 I thought the lowest and more representative for blue channel could be f090W, whilst f444W for red and middle f335M for green.

Before channel combination I did proceed for a star registration of the whole masters, choosing f444W as reference.

I thus integrated all registered frames in percentile clipping and saved the .xifs integration as luminance.

“Simple” [L]RGB is about to end by:

RGB final integration by Process > Channel Management > Channel Combination

LRGB final integration by Process > All Process > LRGB Combination

About more “complex” 6 channel integration I just stretched very lightly by manual Histogram Transformation and export each filter master registered file as .tiff.

Using luminance as bg layer, I thus imported as layer each filter, according to Carver tutorial in screen mode blending with 50% opacity, by adjustment layer/saturation colorizing and boosting/decreasing saturation and luminance trying to respect NIRCAM wavelenght filters charts; take care to change Image > Mode to RGB from greyscale as very first step after luminance opening in Photoshop.

Finally applying an adjustment/curves layers to each filter and retouching pertinent saturation I try to obtain the most balance and well colored images, imho absolutely subjective pov.

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