Expert processing tips to enhance your astrophotos <\/p>\n\n
ASTROPHOTOGRAPHY<\/span><\/h5>\n\n
PROCESSING<\/span><\/h2>\n\n\n\n
APY Masterclass: Cracking a smiley face in space <\/h2>\n\n
The processing routines that created the galactic grin of NGC 1055 <\/p>\n\n A Smiley in Space, the final processed image that won Martin the APY nod<\/figcaption><\/figure>\n\n
Unlike big and bold face-on spiral galaxies such as M101, the Pinwheel Galaxy and M33, the Triangulum Galaxy, NGC 1055 is an edge-on spiral galaxy. Located in the constellation Cetus, the Whale, at a distance of approximately 52 million lightyears, its proximity to two bright stars gives it the nickname \u2018a smiley in space\u2019.<\/span><\/p>\n\n
Described as a galaxy that has a prominent nuclear bulge crossed by a wide, knotty, dark lane of dust and gas, the immediate goal was to collect data in terms of both quality and quantity to be able to reveal these features in detail. Furthermore, a substantial quantity of data will largely suppress \u2018noise\u2019 when the data is combined, and this allows you to push the data further when processing. <\/p>\n\n
I collected more than the 22 hours of RGB and luminance data that went into the final image, but those frames that did not pass my quality threshold were discarded. I have learned that including images with \u2018fat\u2019 stars has a direct impact on the quality of the final image. Luminance data is key. It is from this data that the eye perceives detail, so this was acquired when the galaxy was at its highest in the night sky and only the very best frames were used to resolve the knotty, dark lane of dust and gas.<\/span><\/p>\n\n
Boosting the bulge <\/strong><\/h4>\n\n
My processing goals using Photoshop were to enhance the nuclear bulge and overall colour of the galaxy and stars. Figure 1 (below) is the result of combining the master RGB frames. Colour is looking good, but is somewhat underwhelming and in need of further enhancement. <\/p>\n\n
I duplicated the background to form a new layer then applied the \u2018Match Colour\u2019 filter and set the large stars were excluded as I prefer to deal with those separately.<\/span><\/p>\n\n
A \u2018Reveal Selection Layer Mask\u2019 was added to the star selection and treated to a mild 0.5 pixel Gaussian blur before applying the \u2018Match Colour\u2019 filter. This star layer was set to \u2018Colour\u2019 blend mode and then flattened. Again, this technique was repeated until my desired level of saturation was achieved. Using a layer mask ensured that I did not oversaturate the galaxy and add colour noise to the background (see Figure 2). <\/p>\n\nFigure 1: Initially, the combined RGB frames were a little lacklustre <\/figcaption><\/figure>\n\nFigure 2: Enhancing the overall colour, being careful not to oversaturate<\/figcaption><\/figure>\n\nFigure 3: Improving the galaxy with the luminance data <\/figcaption><\/figure>\n\nFigure 4: The final, selective application of sharpened luminance <\/figcaption><\/figure>\n\n
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3 QUICK TIPS <\/h4>\n\n\n\n
1. <\/strong>Apply the \u2018Match Colour\u2019 technique to the galaxy only, using a selection or mask. <\/p>\n\n\n\n
2. <\/strong>Be careful not to over-sharpen. Sharpen selectively and only on areas of high signal-tonoise ratio. <\/p>\n\n\n\n
3. <\/strong>Mild blurring of the stars helps to restore colour and smooths out pixelation. colour slider to 150. Next, I changed the blend mode of this new layer to \u2018Colour\u2019 then flattened and repeated until I was satisfied with the desired level of colour saturation. I then created a precise star selection and saved that as a new channel. The very <\/p>\n<\/div><\/section>\n\n
Sharpening the dust lanes <\/strong><\/h4>\n\n
Next up was resolving and improving the dust lane, where the high-quality luminance data \u2013 captured separately \u2013 comes into play. I layered the sharpened luminance image on top of the colour image and set the luminosity blend mode opacity to 50 per cent. The two layers were then flattened and the whole image treated to just enough noise reduction to smooth out the noise added by the sharpened luminance. <\/p>\n\n
When adding luminance, the colour can become washed out, so to compensate I applied another iteration of \u2018Match Colour\u2019 but reduced the impact by lowering the opacity of the \u2018Colour\u2019 layer to 50 per cent. The sharpened luminance was then reapplied with the blend mode set to \u2018Luminosity\u2019 at 70 per cent opacity. On this occasion, however, I applied a \u2018Hide All\u2019 layer mask and used the brush tool to reveal the sharpened galaxy only (see Figure 3). <\/p>\n\n
Then it was time to address the colour and size of the two large foreground stars. Here I used the \u2018Ellipse\u2019 tool to draw a selection around the large yellow-white star. I feathered the selection by 15 pixels so that any transitions in colour or texture were smooth. I then applied a curves adjustment, lowering the blue channel only to achieve a deeper yellow. While the selection was still active, I applied a two-pixel radius minimum filter (Filter > Other > Minimum) and set the \u2018Preservation\u2019 option to \u2018Roundness\u2019. This reduced the size of the star, making it less prominent. I repeated this procedure on the blue-white star, but lowered the red channel in the curves adjustment (see Figure 4). <\/p>\n\n
Finally, I reloaded the star selection created earlier and applied a very small amount of unsharp masking to make them shine, producing the final image you can see at the start of this article. <\/p>\n\n
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Martin Pugh has previously won APY awards in 2009 and 2012. Retired from the Navy, he runs his own remote astroimaging business from his home in rural Australia<\/p>\n\n
Photos: MARTIN PUGH<\/p>\n","protected":false},"excerpt":{"rendered":"
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