{"id":44499,"date":"2023-05-11T10:12:43","date_gmt":"2023-05-11T10:12:43","guid":{"rendered":"https:\/\/www.skyatnightmagazine.com\/?p=118597"},"modified":"2023-05-11T12:32:32","modified_gmt":"2023-05-11T12:32:32","slug":"bring-out-beauty-and-detail-in-your-images-of-edge-on-galaxies","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/rss_feed\/bring-out-beauty-and-detail-in-your-images-of-edge-on-galaxies\/","title":{"rendered":"Bring out beauty and detail in your images of edge-on galaxies"},"content":{"rendered":"

Advice from a 2022 shortlisted entrant in the \u2018Galaxies\u2019 category of the Astronomy Photographer of the Year competition. <\/p>

By Jason Guenzel\n \t\t<\/p>

Published: Thursday, 11 May 2023 at 12:00 am<\/p>

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A<\/span> <\/b>backyard astrophotographer will often strive for world-class results. Perhaps it is in our nature.<\/p>\n

But rising to this challenge requires continued improvement in image processing<\/a> techniques and also careful consideration of attainable goals for each project.<\/p>\n

In years past, I was honoured to be recognised and awarded in the annual Astronomy Photographer of the Year exhibition.<\/p>\n

It happened again in 2022 as my image, \u2018Edge-On\u2019, was shortlisted in the \u2018Galaxies\u2019 category.<\/p>\n

It\u2019s interesting to revisit it and consider what makes this particular image stand out above thousands of other submissions.<\/p>\n

The target is NGC 891<\/a>, a beautiful spiral galaxy<\/a> 30 million lightyears distant. Our vantage point lies along the plane of its galactic disc.<\/p>\n

Find out how to improve your image processing<\/a><\/strong><\/em><\/p>\n

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NGC 891 photographed by Jeff Johnson, Las Cruses, New Mexico, USA<\/span><\/figcaption><\/div>\n

We are treated with a spectacular edge-on view: a diffuse stellar halo crossed with a complex, backlit dark dust lane.<\/p>\n

The contrast within these delicate and wispy features creates a visual drama that draws the eye deeper into the galaxy.<\/p>\n

Highlighting this dust was a definite goal from the beginning.<\/p>\n

If we consider each workflow to be a unique creative journey, that artistic vision of the end product can serve as a guide to our processing choices.<\/p>\n

The aim is to simply serve the image, assessing what is needed and continually adjusting course as necessary.<\/p>\n

A capable collection of tools can be used to steer, with subtle corrections, towards that ultimate goal.<\/p>\n

Here is a brief overview of some post-processing concepts for dust lane enhancement, widely applicable to galactic images.<\/p>\n

I started with the raw stack for the monochrome luminance filter, as this channel conveys visual details in the image (see image below).<\/span><\/p>\n

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Ooriginal raw image stack (top) captured with a ZWO ASI1600MM and Celestron 8-inch EdgeHD, 696x 90\u201d, 17.4h total; (middle) the image after RC-Astro\u2019s BlurXTerminator one-click plug-in was applied; and (bottom) after NoiseXTerminator was applied<\/span><\/figcaption><\/div>\n

Deconvolution in PixInsight mathematically sharpens the image based on data contained within.<\/span><\/p>\n

When I originally processed \u2018Edge-On\u2019, I used an elaborate workflow of mask generation and deconvolution.<\/span><\/p>\n

Ultimately this can be replaced by the new BlurXTerminator plug-in from RC-Astro<\/a><\/span>.<\/span><\/p>\n

In reprocessing this photo, I can confirm the results to be directly comparable to my previous process, and with just a single button click!<\/span><\/p>\n

Noise Reduction in PixInsight reduces the noise without destroying fine detail.<\/p>\n

For this demonstration, another RC-Astro tool, NoiseXTerminator, does an excellent job of protecting the details within the galaxy while effectively reducing background noise.<\/p>\n

After stretching and applying colour to the previous result in Photoshop (see image below), I turned to contrast enhancements.<\/p>\n

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The resulting image after stretching and applying RGB colour (left) and with high-pass filtering applied (right) at radius scales 3, 6, 12, 24 and 48 to enhance contrast before blending in \u2018Overlay\u2019 mode as layers in Photoshop<\/span><\/figcaption><\/div>\n

Several software packages are capable, but Photoshop offers the benefit of working in layers of varying opacity while still providing real-time visual feedback.<\/p>\n

Creating projects consisting of many layers using different enhancement processes, and blending them into each other in creative ways, can yield results unobtainable with single processes executed in a serial fashion.<\/p>\n

One effective method of multi-scale contrast enhancement is high-pass filtering.<\/p>\n

Start by duplicating the original layer. With the new layer selected, navigate to Filter > Other > High pass<\/strong><\/em>.<\/p>\n

The Radius<\/strong><\/em> slider allows you to choose the scale of the effect (smaller radii will emphasise smaller structures).<\/p>\n

Click Ok<\/strong><\/em> and then change the blending mode of the layer to Overlay<\/strong><\/em> (or Soft light<\/strong><\/em> for less effect).<\/p>\n

The layer opacity can be lowered to provide a subtle contrast enhancement.<\/p>\n

I repeated this technique multiple times at different radius scales and layer opacities.<\/p>\n

I used masks to limit the effect to exactly where it was needed in the galactic core (see image above).<\/p>\n

Other interesting tools to try for local contrast enhancement include:<\/p>\n