NGC 3324: approaching JWST raw data (.fits) for post-production attempt
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
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:
- a “simplified” RGB or LRGB image integration by channel combination
- 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.
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.
