{"id":43718,"date":"2023-04-18T14:13:18","date_gmt":"2023-04-18T14:13:18","guid":{"rendered":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/?post_type=purple_issue&p=43718"},"modified":"2023-04-27T14:54:04","modified_gmt":"2023-04-27T14:54:04","slug":"capturing-the-magnificent-milky-way","status":"publish","type":"post","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/2023\/04\/18\/capturing-the-magnificent-milky-way\/","title":{"rendered":"Capturing the magnificent Milky Way"},"content":{"rendered":"\n
\"\"<\/figure>\n\n

Capturing the magnificent Milky Way<\/h2>\n\n

Get ready for the return of late summer nights under the stars, as Will Gater <\/strong>presents a beginners\u2019 guide to photographing our ever-changing home Galaxy<\/p>\n\n

As the lighter nights begin to swing around in May, one thing I like to do is fire up Stellarium and plan out all the things I want to photograph when proper darkness returns in the late summer. Almost always, the target that occupies me the most, no matter how many times I\u2019ve imaged it, is the Milky Way. Widefield, nightscape or long-focal-length close-up \u2013 it doesn\u2019t matter what format we\u2019re talking about, there\u2019s always something our Galaxy can offer. <\/p>\n\n

\"\"
Whether you\u2019ve got basic kit or full bells-and-whistles tracking gear, we\u2019ll help you get great images of our glorious Galaxy <\/figcaption><\/figure><\/div>\n\n

It\u2019s important to think ahead when it comes to Milky Way imaging. The view changes from month to month, week to week and even hour to hour throughout the night. And the best time to photograph our Galaxy from the UK, in my opinion, is the first weeks of August. Not only has astronomical darkness come back for most of us in the UK by that point, but you also don\u2019t have to wait all night for the band of the Milky Way to be positioned close to the meridian. Plus, from a composition perspective I love how the core of the Galaxy and the swathe of its spiral arms, arcing up into the eastern sky, are positioned as midnight approaches. <\/p>\n\n

If you\u2019ve never dipped your toes into the waters of Milky Way astrophotography, now\u2019s the perfect time to get prepped for this season. So read on as we introduce you to shooting the spectacular celestial metropolis that we all call home. <\/p>\n\n

Use the right kit <\/strong><\/h4>\n\n

You can achieve spectacular images even with a fairly modest setup <\/strong><\/p>\n\n

One of the really nice things about photographing the Milky Way is that there are lots of ways to do it, with lots of different types, and levels, of equipment. This means it\u2019s one of those targets that you can start off imaging as a beginner and keep coming back to year after year as you get more experience, often finding new and different ways of doing things as you do. <\/p>\n\n

The remarkable recent advances in smartphone camera tech mean it\u2019s now possible to get fantastic widefield images of the Milky Way using some of the high-end models equipped with low-light imaging modes. For many new astrophotographers, another common entry point into imaging is with something like an off-the-shelf DSLR or bridge camera with a stock wide-angle lens. This kind of kit, combined with a normal photographic tripod, is a brilliant way to start capturing basic portraits of the Milky Way, particularly if the lens is fast \u2013 that is, if the f-ratio it can achieve when the lens aperture is set wide open is relatively low, say in the region of f\/2\u20133 or thereabouts. A 30-second exposure using a medium-to-high ISO setting \u2013 let\u2019s say 1600 to 6400 \u2013 with such a setup will easily bring out great detail in the rich star fields and silhouetted dust lanes of the Milky Way from a dark site.<\/span><\/p>\n\n

Beyond widefield Milky Way nightscapes, though, the challenge with shooting with a static tripod is that if you want to use a longer exposure \u2013 to go deeper and capture more, faint, details \u2013 you run into the problem of the sky rotating and stars trailing. Now, you can get around this by taking your shorter exposures and stacking them in software to improve the signal-to-noise ratio (and then doing some clever compositing using layer masks, if you\u2019re shooting with a landscape in the frame). But the other approach is to progress to mounting or piggybacking your camera on a driven telescope mount or a smaller, portable tracking mount. <\/p>\n\n

\"\"
Pocket pro: got a high-end smartphone with low-light settings? Just add a mount and beautiful Milky Way shots can be yours <\/figcaption><\/figure><\/div>\n\n
\"\"
Once you\u2019ve mastered tracking, you\u2019ll get fine, pin-sharp stars like in this shot of Lyra and the surrounding star field and dust lanes <\/figcaption><\/figure>\n\n

Track for longer shots <\/strong><\/h4>\n\n
\"\"
A DSLR on a tracking mount will allow you to take longer shots that avoid star trailing <\/figcaption><\/figure><\/div>\n\n

This allows you to do two things: first, it enables you to drop down to a slightly lower ISO setting while dialling up the exposure length, so any resultant single image is less noisy \u2013 particularly useful for nightscapes. And, secondly, it opens up those much longer exposures more generally \u2013 we\u2019re talking several minutes at a time here \u2013 because now the mount is cancelling out Earth\u2019s rotation and keeping the stars point-like; with this, you can then take multiple long-exposure sub-frames and stack them together to create detail -rich, deep, widefields of the Milky Way star fields or areas embedded within them.<\/span><\/p>\n\n

The big variable once you get to this type of Milky Way photography, then, is the focal length of the lens you\u2019re using. In the collage below, we\u2019ve highlighted three examples of Milky Way imaging styles at different focal lengths. A 24mm lens gives us a big field of view to work with on a full-format DSLR, which is ideal for wide shots of large swathes of the band of the Galaxy, both on a static tripod or tracking mount. The 50mm lens, meanwhile, can be used for slightly more focused nightscapes on a particular area of the Milky Way, in that case the Galactic core. <\/span><\/p>\n\n

But it\u2019s also a great focal length for capturing deep images of dark dust lanes weaving through the Milky Way\u2019s granular spiral arms or prominent constellations through stacking multiple exposures. The last image was taken using a 135mm lens. Focal lengths of 100mm upwards naturally provide much narrower fields of view, so they are best suited to putting deep-sky objects, like clusters and nebulae, in the context of broader Milky Way star fields \u2013 the summer and autumn skies in particular provide a wealth of targets for this kind of work.<\/span><\/p>\n\n

\"\"
The Milky Way captured at three different focal lengths: 24mm for a wide view, 50mm for closer-in and 135mm to highlight a region <\/figcaption><\/figure>\n\n

Plan for perfection <\/strong><\/h4>\n\n
\"\"
Stellarium (left) and SkySafari (right) are both excellent apps to help you plan your nights of imaging<\/figcaption><\/figure><\/div>\n\n

Spending time planning your shots will vastly improve your results <\/strong><\/p>\n\n

Before you go anywhere near the camera shutter button, spend some time planning the composition of your Milky Way images, whether they\u2019re nightscapes or more complex captures using a driven mount. Software and apps \u2013 such as The Photographer\u2019s Ephemeris, Stellarium and SkySafari Plus \u2013 will show you where the band of the Milky Way will be in the sky at what time, and the last two also have camera field of view tools that can help you scope out framings with your chosen kit. <\/p>\n\n

Pick your settings <\/strong><\/h4>\n\n

With so much variation in the kind of equipment you could use to shoot the Milky Way, it\u2019s not possible to give a \u2018standard\u2019 starting exposure length or ISO setting to use. Instead, the way I\u2019d recommend approaching it is through experimentation, trying to find a good balance between the aperture setting of the lens, the exposure length and the ISO value. For example, opening the lens aperture right up will gather more light, yes, but it will also, on most models, result in more obvious artefacts like the dimming of the corners and frame edges, known as \u2018vignetting\u2019. It can also exacerbate star distortion around the edge of the frame. Meanwhile, set the ISO too high or too low and you either bring in a lot of noise or don\u2019t get the <\/span>detail you need. And then there are the sky conditions, like light pollution and transparency, whose variable effects you\u2019ll need to factor into these considerations.<\/span><\/p>\n\n

Capturing the data is only part of photographing our Galaxy, however. The post-processing of that imagery is where it can really come to life. We\u2019ll get onto processing in a moment, but for widefield Milky Way work there\u2019s one common problem that often comes up: gradients, either from the optical system or from light pollution in the sky, or often both. <\/p>\n\n

\"\"
How to remove gradients (to rectify light pollution or vignetting from your optics) if your software doesn\u2019t have a dedicated tool <\/figcaption><\/figure>\n\n

Grapple with gradients <\/strong><\/h4>\n\n

To tackle vignetting, you can take some very \u2013 and I stress very <\/em>\u2013 rudimentary flat fields by focusing the lens at infinity and then taking some well-exposed images of a smooth, plain and evenly illuminated white interior wall, which you can use to calibrate data in stacking software later. <\/p>\n\n

\"\"
Create your own basic flat field images by simply shooting a plain, white wall <\/figcaption><\/figure><\/div>\n\n

If the astronomical processing software you\u2019re using doesn\u2019t have a built-in gradient removal tool for any remaining gradients, here\u2019s one way to tackle moderate gradients in a program like Photoshop: first duplicate your image as a new layer. Then use a \u2018Dust & scratches\u2019 removal tool to remove all the stars. Then clone out, with the clone or heal tool, any remaining bright stars and Milky Way features in view. Next apply a fairly strong Gaussian blur to the centre 80\u201390 per cent of the frame using a marquee tool and then \u2018Select and mask\u2019, followed by the blurring filter. Now place this image in the layer below the original image layer <\/span>and use \u2018Image > Apply image\u2019 with the blending mode set to \u2018Subtract\u2019. Copy the resultant image into a new layer and process it to taste.<\/span><\/p>\n\n

\"\"
The \u2018Dust & scratches\u2019 tool in Photoshop can be used to remove the stars <\/figcaption><\/figure><\/div>\n\n

<\/p>\n\n

<\/div>
\n

Create a portrait of the summer Milky Way<\/h4>\n\n\n\n

Using a wide lens, DSLR or bridge camera, a tracking mount and a little processing <\/p>\n\n\n\n

\"\"<\/figure><\/div>\n\n\n\n

Step 1 <\/strong><\/h4>\n\n\n\n

To fully capture the incredible granular Milky Way star fields, it\u2019s crucial to devote time to getting the focus spot on. If you\u2019re using a live preview screen for focusing, don\u2019t use stars around the periphery of the frame to focus on, as often with wide-angle lenses optical aberrations make it harder to perceive the exact focus point. <\/p>\n\n\n\n

\"\"<\/figure><\/div>\n\n\n\n

Step 2 <\/strong><\/h4>\n\n\n\n

If you haven\u2019t already done so, plan your composition in planetarium software (eg Stellarium). Now set your camera to a very high ISO and use short exposures to capture some test shots. For this kind of image it\u2019s best not to include any earthly foreground, unless you are happy with it being blurred when we stack frames later. <\/p>\n\n\n\n

\"\"<\/figure><\/div>\n\n\n\n

Step 3 <\/strong><\/h4>\n\n\n\n

Change the ISO and exposure length to the settings you need to capture your sub-frames. These will be the level at which there\u2019s a good balance between the amount of detail you\u2019re getting in the star fields and the \u2018fogging\u2019 effect of any light pollution at your site. There\u2019s no one-size-fits all, so experimentation is key. <\/p>\n\n\n\n

\"\"<\/figure><\/div>\n\n\n\n

Step 4 <\/strong><\/h4>\n\n\n\n

With a suitable exposure length and ISO selected, capture at least 10\u201315 minutes\u2019 worth of data in total when shooting your main data. More sub-frames to stack later will help you create a smoother final image, something that\u2019s especially important if you\u2019re shooting at a high-ISO setting on a static tripod. <\/p>\n\n\n\n

\"\"<\/figure><\/div>\n\n\n\n

Step 5 <\/strong><\/h4>\n\n\n\n

Once you\u2019re back home, consider if you\u2019ll need some \u2018flat field\u2019-style calibration frames with the lens you used (see above for more details). When you have your data loaded onto your computer, inspect each sub-frame carefully and set aside any that show signs of cloud passing through the shot, mount vibrations or wind blurring. <\/p>\n\n\n\n

\"\"<\/figure><\/div>\n\n\n\n

Step 6 <\/strong><\/h4>\n\n\n\n

You should now have a folder of image files that you\u2019ve inspected that represent the best frames from your capture sequence. You can now add, or stack, these together in dedicated astronomical processing software, whether that be free programs like DeepSkyStacker or commercial options like Nebulosity or PixInsight. <\/p>\n\n\n\n

\"\"<\/figure><\/div>\n\n\n\n

Step 7 <\/strong><\/h4>\n\n\n\n

A good first step is to enhance the contrast and brightness of your stacked shot via a gentle Levels or Curves \u2018stretch\u2019. Using the Curves tool in a program like Photoshop, adjust the diagonal line so that it takes on a subtle \u2018s\u2019 shape, bringing up the brighter elements of the image while increasing the contrast in the shadowier parts. <\/p>\n\n\n\n

\"\"<\/figure><\/div>\n\n\n\n

Step 8 <\/strong><\/h4>\n\n\n\n

If the post-processing software you\u2019re using doesn\u2019t have gradient or vignetting removal tools, you can do basic gradient removal using the technique outlined above. You may then want to return to step 7 to do another round of contrast and brightness enhancements (on the hopefully now-improved image) . <\/p>\n\n\n\n

\"\"<\/figure><\/div>\n\n\n\n

Step 9 <\/strong><\/h4>\n\n\n\n

Finish with basic colour balancing of your picture. Look for bright(ish) stars in your framing that have a neutral white spectral type (using software like Stellarium as a reference). Then use a colour balance tool in your processing software to adjust the picture\u2019s overall colour so that the stars\u2019 hue is as close to neutral white as possible. <\/p>\n<\/div><\/section>\n\n

\n\n
\"\"<\/figure><\/div>\n\n

Will Gater <\/strong>is an astronomer, writer and astrophotographer.
Visit his website willgater.com<\/a> or follow him on Twitter: @willgater <\/a><\/p>\n\n

<\/p>\n\n

PHOTOS: @THESHED_PHOTOSTUDIO, WILL GATER, INDYSYSTEM\/ISTOCK\/GETTY IMAGES, M-GUCCI\/ ISTOCK\/GETTY IMAGES, SKY SAFARI, STELLARIUM <\/p>\n","protected":false},"excerpt":{"rendered":"

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