Astronomy Now - January 2021

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Nik Szymanek

Imaging Masterclass: From pixels to

gigapixels (part 2 )

ast issue we used Topaz Labs’ Gigapixel AI to resample some daytime DSLR images and then
assessed the end result after enlargement. e images passed muster with ying colours,
outperforming the resampling tools in both Photoshop and Affinity Photo. is issue, we’ll examine its
performance on deep-sky astro-images, and things are going to get really interesting in a way that I
certainly wasn’t expecting.

My curiosity about Gigapixel AI was piqued by the fact that when I’m imaging in my back-garden
observatory I tend to bin my CCD camera into a 2 × 2 conguration. is works well since it makes
the camera more sensitive and the pixel sampling rate matches the typical seeing conditions. e
end result, though, is quite a small le, around 1,663 × 1,252, which just lls my PC screen when
shown at 100 per cent. And, of course, resampling is required for any poster or large-print
production. Having good software to x this is important, so let’s see how well Gigapixel AI performs
on the deep sky.

I started by calling up a 2 × 2 binned LRGB image of the beautiful galaxy Messier 81 in Ursa Major
(Step 1). A quick application of Gigapixel AI to enlarge it by 2× produced an intriguing result. After
manipulating the ‘Suppress Noise’ and ‘Remove Blur’ sliders I was very surprised to see that not only
had it performed very well in terms of resampling, but it had also sharpened the image, better
resolving the detail in the spiral arms and tightening up the star images and diffraction spikes.
Further, the image was smoothed, with no loss of resolution (see the right pane in Step 1). is
really piqued my interest, so I opened another image taken a few years ago from the AstroCamp
remote observatory in Spain. e galaxy featured in that image is Messier 82, which is also in Ursa
Major, and this image in particular is an extremely deep LRGB image combined with hydrogen-
alpha data to capture the bipolar outburst from the galaxy’s core. I applied 2× resampling and then
once again adjusted the two sliders and was amazed at the level of detail that popped out of the
image (Step 2). is was particularly evident in the dark, dusty tendrils emanating along the plane
of the spiral arms and in the outow material. As before, star images improved, as did the diffraction
spikes. And, yet again, the image was smoothed remarkably well.

I certainly had not expected these enhancements from a resampling software package. When I
compared the before-and-after views shown in Steps 1 and 2, I was once again reminded of
deconvolution software, whose raison d’être is to eke out resolution from blurry images. Gigapixel AI
does that almost as an afterthought and with no ugly ‘ringing’ around the stars.

For the next test, I wanted to try resampling an image that contained lots of stars as well as
nebulosity. For this, I used an image of the famous Eta Carinae Nebula that was taken with the
Telescope Live remote-imaging platform in Australia. Using a Takahashi FSQ-106 premium
refractor coupled with an FLI PL16803 large-format CCD camera and Astrodon narrowband lters,
the entire nebula was visible in a single frame. Step 3 shows the image in the left-hand pane. I
usedGigapixel AI to resample the image by 2× and then cropped it to home-in on the lovely emission
nebula NGC 3324, which is seen at the top left. e centre pane shows the enlarged original crop
zoomed in to 200 per cent to match the scale of the 2× resampled version, shown in the right-hand
pane. e original image is quite pixelated, but the resampled version shows great stars and nebulae
with just a small amount of smoothing.

Next, I opened a Milky Way image taken under La Palma’s dark sky with a Canon 5D MkII DSLR
and made up of ten 300-second exposures stacked together. Once again, I applied a 2× resample and
adjusted the sliders to get the result shown in Step 4. To obtain this image, I’d pre-focused the lens
in twilight using the camera’s auto-focus capability and taped the lens barrel in place. is method
delivers the sharpest star images. On the left is the original image, showing the famous ‘Pipe
Nebula’ (also known as Barnard 59, 65–67 and 78) and on the right is the resampled and slider-
tweaked preview. It’s quite similar (no mean feat for a 2× resample) and has slightly sharper stars.

Clicking on ‘Save’ processed the image. I should mention that when using this program it doesn’t
save the image as a new state (like the other Topaz Labs programs) but creates a new layer. You can
hide the new layer to see the preprocessed version and compare the two. Intriguingly, both states are
shown as the same size. I’m not sure how that’s done, but it makes the comparison very easy.

If I’m happy with the result, then I atten the image into a single layer, hiding the original image.
It’s then a simple matter to just save the new image (Step 5).

is concludes our articles on the use of Topaz Labs software for deep-sky and DSLR images. I’ll
summarise them thus: Sharpen AI does brilliant sharpening with high-quality noise reduction;
DeNoise AI proves to be brilliant at noise reduction with high-quality sharpening; and Gigapixel AI is
brilliant at resampling with high-quality sharpening and noise reduction.

I think that all of these programs deliver good value for money. ey come with free updates for one
year and since I started using them several months ago, all three have had several updates. Each
program takes quite a bit of hard-disk space and when an update is carried out, the download is
around 1.5GB; this is presumably so large because it is replacing the earlier version. With a
reasonably fast broadband speed it doesn’t take too long. Some user participation is required as each
of the programs works slightly differently on the input images. At times, I found the applied effects
to be quite subtle and requiring further experimentation, but all three user interfaces are simple and
intuitive to use. In a lot of cases the ‘Auto’ settings seem to work pretty well. I did have the
occasional glitch following an update – for example, after one update Gigapixel AI wouldn’t run as a
plug-in for Photoshop, but this wasn’t a big issue since it worked perfectly well as a standalone
program. e next update xed the problem.

Step 1: Before (left) and after views of M81, which is a lovely spiral galaxy in Ursa Major. This image was taken with a GSO 254mm
Ritchey- Chrétien telescope, with 22 hours total exposure time through Astrodon LRGB and hydrogen-alpha lters. The left pane is
the original image captured with a QSI 583wsg CCD camera binned 2× 2. The right-hand pane shows 2× resampling with
sharpening and smoothing applied. All images: Nik Szymanek.

Nik Szymanek resampled some of his deep-sky images using Topaz Labs’ Gigapixel AI software,

and found that it has a surprising sharpening ability too.

Step 2: The enigmatic galaxy M82 in Ursa Major. After resampling the image 2× and carefully manipulating the sliders, the core
detail of the galaxy was enhanced, smoothing any background noise and tightening the diffraction spikes. This LRGB/hydrogen-
alpha image was taken remotely with an Ikharos 254mm Ritchey-Chrétien telescope and a QSI 683wsg CCD camera from AstroCamp
in Nerpio, Spain.

Step 3: The famous Eta Carina Nebula, imaged remotely from Heaven’s Mirror Observatory in Australia using Telescope Live’s
Takahashi FSQ-106 refractor coupled with an FLI PL16803 CCD camera and Astrodon narrowband lters. The centre pane shows the
image cropped and enlarged, featuring NGC 3324, which is a part of the Eta Carina Nebula. The right-hand pane shows the 2×
resampled image viewed at 100 per cent and is clearly smoother and non-pixellated.

Step 4: A tough test for resampling software are the rich star elds of the summer Milky Way in Sagittarius. Shown here is Barnard
59, 65-67, and 78, dark nebulae collectively known as the Pipe Nebula. The 2× resampling shown in the right-hand preview
window has done a great job, keeping the stars crisply dened and the sky free from background noise.

Step 5: The complete Milky Way image after 2× resampling. The image was taken with a Canon 5D MkII DSLR camera and 28mm
lens on an AstroTrac TT320 Star Tracker mount from La Palma in the Canary Islands, with 10 ve-minute exposures stacked in Deep
Sky Stacker. An image like this could be printed as a moderately large poster (A2, or possibly larger) after resampling.

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Imaging Masterclass: From pixel...

January 2021

Astronomy Now