{"id":33702,"date":"2022-07-20T00:00:00","date_gmt":"2022-07-20T00:00:00","guid":{"rendered":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/?post_type=purple_issue&p=33702"},"modified":"2022-07-21T14:12:15","modified_gmt":"2022-07-21T14:12:15","slug":"12-astrophotography-pitfalls-to-avoid","status":"publish","type":"post","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/2022\/07\/20\/12-astrophotography-pitfalls-to-avoid\/","title":{"rendered":"12 Astrophotography pitfalls to avoid"},"content":{"rendered":"\n

Expert astrophotographer Will Gater <\/strong>runs through the common mistakes even experienced photographers make and how to ensure your next imaging session is free of them <\/p>\n\n

\"\"
When beautiful skies are waiting, don\u2019t be caught out with flat batteries and an uncollimated telescope <\/figcaption><\/figure>\n\n

Starting out in astrophotography is an exciting, but often bewildering, experience. When you think about it, it\u2019s probably one of the strangest types of photography out there.<\/span><\/p>\n\n

You\u2019re going out, in the dark, at night \u2013 sometimes in remote spots \u2013 trying to capture a picture of something that\u2019s not only really distant but extraordinarily faint by any normal photographic standard. <\/p>\n\n

Oh and, by the way, not only will the entire sky be moving while you\u2019re doing this, but the atmosphere you\u2019re shooting through will be wobbling too. And that\u2019s before you\u2019ve even considered the prospect of actually processing the data you\u2019ve captured. <\/p>\n\n

It\u2019s no wonder there are so many slip-ups that it\u2019s easy to make. In this piece I\u2019m going to look at 12 common imaging mistakes and how you can avoid making them. I\u2019ve made every single one of them myself at one point or another, and I\u2019m sure in time you\u2019ll find new and interesting ones of your own too \u2013 the astrophotography learning process is one that never ends! <\/p>\n\n

1. Not getting the focus right and capturing soft data <\/strong><\/h4>\n\n

<\/p>\n\n

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The exagerrated spikes created by a Bahtinov mask are another way to achieve sharp focus<\/figcaption><\/figure><\/div>\n\n

As imagers we often dedicate tens of hours, if not more, to setting up a scope and mount, getting the auto-guiding or tracking just right and then carefully processing the data we capture. But the quality of the final image all hinges on a pivotal process that can all too easily be rushed: getting the optics perfectly <\/em>focused. If you\u2019re not using a focusing aid \u2013 such as a Bahtinov mask \u2013 time spent carefully confirming focus will never be wasted. When doing this, try to slowly adjust the focuser a little way past what you think is the focus point, and then gradually return back through to the other \u2018side\u2019 of that point until you\u2019re absolutely sure where it is. <\/p>\n\n

If you\u2019re using a live preview screen on a camera, check focus on several medium-bright stars in the frame, as sometimes it\u2019s not easy to accurately judge when a bright star is at its smallest and, therefore, sharpest. And once you\u2019re focused, continue to check that the optics you\u2019re using remain <\/em>in focus throughout your imaging session. Did you very slightly nudge the focus ring on the lens as you manoeuvred the camera around, for example? <\/p>\n\n

Has the focus of your imaging system changed minutely as the air temperature has varied? Did a filter change alter the focus point? Athough they can be time-consuming, all of these little checks, will ensure the data you capture is the clearest and crispest it can be.<\/span><\/p>\n\n

2. Not letting optics cool <\/strong><\/h4>\n\n
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Your scope needs time to adjust to outside temperatures <\/figcaption><\/figure><\/div>\n\n

With clear skies a rarity in the UK, it\u2019s understandable you\u2019d want to start imaging as soon as you\u2019ve got your kit outside. However, it\u2019s essential to allow a telescope\u2019s optics to cool down to close to the ambient air temperature before you do, particularly in the case of highresolution lunar and planetary imaging. <\/p>\n\n

This is because air currents inside a warm telescope can degrade any data you capture, making the final image softer. If it is safe to and there\u2019s no risk of inclement weather (and there\u2019s a clear night ahead), put the covered telescope outdoors in advance of your imaging session and you\u2019ll get better results. <\/p>\n\n

3. Clipping the black point in post-processing <\/strong><\/h4>\n\n
\"\"
The same data, processed differently. In the bottom image the black point has been \u2018clipped\u2019 causing a loss of detail <\/figcaption><\/figure><\/div>\n\n

Here we come to our first \u2018mistake\u2019 which is concerned with something a little more aesthetic than practical, and it centres on how we wish to represent space in our images. <\/p>\n\n

When it comes to the depictions of areas around celestial targets, or the night sky more generally, I\u2019m of the view that \u2013 in most kinds of astrophoto \u2013 space, and the night sky, should never be completely <\/em>black. The sky, the Galaxy and beyond is full of the diffuse light of stars and other sources, and so to make the background of an astro image a solid black doesn\u2019t seem quite right. <\/p>\n\n

Now you may disagree on aesthetic or artistic grounds, in which case I very much respect your choice, but if you\u2019ve never considered this before, check that you\u2019re not inadvertently \u2018clipping\u2019 the black point. This is where the contrast of an astrophoto is tweaked to a stage where, when you inspect the \u2018levels\u2019 tool of an image editor like Photoshop or GIMP, the so-called \u2018black point\u2019 arrow slider cuts off the left edge of the levels histogram. This results in subtle, darker shades in the picture being lost and appearing simply as solid black. This is something to watch out for in deep-sky and nightscape imaging in particular, as it can lead to a loss of detail in shadowy features like dark nebulae. <\/p>\n\n

4. Not planning your composition <\/strong><\/h4>\n\n
\"\"
Imagine the scene divided up as above and position your key elements at or near the lines and intersections of the grid <\/figcaption><\/figure><\/div>\n\n

Composition is one of the easiest things to overlook in imaging, yet it has a huge effect on the impact of an astrophoto. If you\u2019re setting up a shot, spend some time thinking about how you\u2019ll draw the viewer\u2019s eye into the picture and how the object or scene you\u2019re shooting is placed in the frame. For nightscapestyle work, with a horizon and foreground, it can be useful to think about the \u2018rule of thirds\u2019 principle, where you arrange features or landmarks into three zones, with key features that you want to highlight placed close to the points where a set of lines cross near the centre of the shot (see below). For deep-sky imaging, offsetting an object from the centre of the frame will often create a more engaging composition than simply placing it right in the middle. <\/p>\n\n

5. Using poorly collimated optics <\/strong><\/h4>\n\n
\"\"
Targets won\u2019t appear sharp if your mirrors are out of alignment <\/figcaption><\/figure><\/div>\n\n

If you\u2019re imaging with a reflecting telescope, it\u2019s really important to regularly check the collimation \u2013 or alignment \u2013 of its optics if you want to take the best images you can. <\/p>\n\n

This is especially important when carrying out long focal-length, high frame-rate imaging of the Moon and planets. There are numerous online collimation guides for a variety of different telescope designs, and experienced members of your local astronomical society may also be able to offer advice if you get stuck. <\/p>\n\n

6. Over-sharpening your data <\/strong><\/h4>\n\n
\"\"
It\u2019s all too easy to over-sharpen objects like lunar craters. Avoid that harsh and \u2018crunchy\u2019 look (right) by making adjustments incrementally and taking breaks from your processing <\/figcaption><\/figure><\/div>\n\n

When you\u2019ve spent so much time collecting precious imaging data it\u2019s tempting to push it as hard as you can in the later post-processing stages: you naturally want to see if you can get as much detail as possible out, but it\u2019s remarkably easy to sometimes take it a step too far. Often you might not even notice what\u2019s happened in that moment when you\u2019re sitting at your computer, deep in thought about the processing. I know I\u2019ve certainly done it with my own pictures, and it\u2019s only when I\u2019ve posted the image online, or seen it on my website, that I think, \u201cHang on, that\u2019s a bit overdone\u201d. <\/p>\n\n

Although one can push data too far in any field of astrophotography, I find it\u2019s particularly easy to do in areas where we\u2019re dealing with data that, from the beginning, has to be refined and sharpened to make fine details visible, like high-frame-rate \u2018lucky\u2019 imaging of the Moon and planets. Here \u2013 when you\u2019re wavelet sharpening or applying an \u2018unsharp mask\u2019 later in an image editor \u2013 nudging the sliders a little too much can quickly result in sharpening artefacts, like dark borders around features or a general \u2018crunchy\u2019 look. <\/p>\n\n

To be vigilant, I find it\u2019s good to make adjustments incrementally, going back and forth to check each step, and then leave the image for a while. When you come back to it with fresh eyes and compare it to earlier iterations, you\u2019ll see if you\u2019ve really made the enhancements you want. <\/p>\n\n

7. Not recceing a site before visiting at night <\/strong><\/h4>\n\n
\"\"
Check out your imaging site before nightfall for potential hazards <\/figcaption><\/figure><\/div>\n\n

If you\u2019re planning on travelling to a new dark-sky spot or one you haven\u2019t visited for a while, recce the site beforehand in daylight. Not only should this help you identify safety issues and avoid hazards, but if you\u2019re a nightscape imager it\u2019ll also give you a chance to scout out compositions. > <\/p>\n\n

8. Not shooting in RAW with your DSLR <\/strong><\/h4>\n\n
\"\"
Shooting in RAW captures far more data, which you can then reprocess time and again <\/figcaption><\/figure><\/div>\n\n

One of my biggest regrets from my early days of digital astrophotography was not shooting in RAW format when using my first DSLR. While I can go back to the vast majority of the DSLR images in my archives and process the RAW files from scratch again \u2013 with the benefit of experience and new processing software or techniques \u2013 the images from those early years are just standard JPEG files, which by their nature are compressed. The RAW format files preserve much more data, so it\u2019s similar to having a digital negative, while if you try to process an <\/p>\n\n

9. Not gathering calibration files <\/strong><\/h4>\n\n
\"\"
Taking flat-field frames lets you remove defects such as vignetting and dust shadows <\/figcaption><\/figure><\/div>\n\n

In a similar vein to neglecting to shoot in RAW, is the issue of capturing calibration files. This is mainly applicable to deep-sky imaging with a telescope or long lens, and it\u2019s one of those occasions when a little effort can have a big effect on an image. In basic terms there are two kinds of calibration files that are worth capturing as a beginner: \u2018flats\u2019 and \u2018dark frames\u2019. <\/p>\n\n

Flats, or flat fields, are images used to capture the optical defects in the imaging system, such as dust shadows on the camera sensor and vignetting (the darkening in the periphery of a frame caused by the optical housing of the telescope). old JPEG you\u2019re essentially working with an inferior copy of the full data captured by the camera. Even if you don\u2019t have the software or intention to process RAW files now, I\u2019d still recommend shooting in RAW, as years down the line you may wish to revisit the data to see what\u2019s lurking in it.<\/span><\/p>\n\n

Flats can be captured using a clean, white cloth or pillowcase carefully placed over the front aperture of your telescope; you then shine a torch onto the cloth and take a well-exposed image. <\/p>\n\n

Dark frames are exposures taken under the same settings and conditions as regular subexposures, except the lens cap or telescope aperture is covered so as to only record the camera noise. In both cases these frames are then subtracted by software when it comes to processing the data, and the calibration they provide will substantially improve the quality of even a basic deep-sky photo. <\/p>\n\n

10. Not preparing contingency kit <\/strong><\/h4>\n\n
\"\"
Flat batteries, full SD cards and missing kit can all ruin your imaging trip <\/figcaption><\/figure><\/div>\n\n

There\u2019s nothing that ruins a night of astrophotography like turning up to an observing site with a camera that doesn\u2019t have a memory card in it or that has a flat set of batteries. My greatest triumph in this area was driving over an hour to a dark-sky spot with my entire imaging rig except the small \u2013 but <\/span>absolutely <\/em>vital <\/em>\u2013 baseplate that holds the DSLR to the tripod head. It\u2019s so easily done. Alarm reminders on my phone throughout the 24 hours before an imaging trip are one way I now build in contingencies to avoid these things happening, as they\u2019re harder to forget or overlook than a physical checklist.<\/p>\n\n

11. Forgetting dew protection <\/strong><\/h4>\n\n
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A lens warmer will keep dew at bay and stop your lens from fogging up <\/figcaption><\/figure><\/div>\n\n

If the atmospheric conditions are right, dew forming on the exposed surfaces of camera lenses and other optics can stop an imaging session in its tracks, sometimes over the course of taking just a few sub-exposures. If you\u2019ve spent a long time setting up or waiting for skies to clear, this can be really demoralising, so it\u2019s good to be vigilant. What\u2019s more, on some nights even dew shields won\u2019t be enough to stop moisture from forming on a telescope or camera lens. There are many active dew prevention systems on the market. These typically work by wrapping around the telescope tube or lens and giving off a very gentle heat, which inhibits the formation of dew on the optics. It\u2019s worthwhile investigating even a basic system, as it should give you several happy hours of dew-free data capture.<\/span><\/p>\n\n

12. Applying excessive noise reduction <\/strong><\/h4>\n\n
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This image of the Lagoon Nebula shows how very strong noise reduction (left-hand side) can make for overly smoothed results <\/figcaption><\/figure>\n\n

I\u2019ll caveat this last point by saying that there\u2019s no \u2018right\u2019 answer and what follows is my opinion, but it is something that beginner imagers are perhaps being too hard on themselves about, thinking they need to make their data look \u2018perfect\u2019. When I look at astrophotos online I often see some that have had very strong noise reduction filters applied, giving the shot a really smoothed look. Personally, I\u2019m not bothered by a little noise in an image and I\u2019d much prefer it over a highly smoothed background \u2013 in some ways the noise is part of the \u2018story\u2019 of the shot. So if you\u2019re tempted to massively crank up the noise reduction filter, maybe, instead, think about what leaving some of it in will bring to the picture.<\/span><\/p>\n\n

<\/p>\n\n

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

Will Gater is an astronomy journalist and science presenter. His latest book, The Mysteries of the Universe, is published by DK<\/p>\n\n

<\/p>\n\n

WILL GATER, STEVE MARSH<\/p>\n","protected":false},"excerpt":{"rendered":"

The common mistakes even experts make and how your next imaging session can be problem-free<\/p>\n","protected":false},"author":24,"featured_media":33688,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"ub_ctt_via":"","purple_page_number":"60","purple_custom_meta_purple_page_number":"60","purple_seq_number":"1","purple_custom_meta_purple_seq_number":"1","purple_source_article":"article_60-1.xml","purple_custom_meta_purple_source_article":"article_60-1.xml","purple_source_issue":"August-2022","purple_custom_meta_purple_source_issue":"August-2022","purple_external_id":"August-2022-60-1","purple_custom_meta_purple_external_id":"August-2022-60-1","purple_issue_code":"|0000086555||","purple_custom_meta_purple_issue_code":"|0000086555||","purple_android_product":"com.im.skyatnight.207","purple_custom_meta_purple_android_product":"com.im.skyatnight.207","purple_ios_product":"com.im.skyatnight.207","purple_custom_meta_purple_ios_product":"com.im.skyatnight.207","purple_web_product":"","purple_custom_meta_purple_web_product":"","purple_publication_id":"075fab74-0a21-4201-866a-899d6c41c40c","purple_migrated":"","kt_blocks_editor_width":""},"categories":[21],"tags":[14],"featured_image_src":"https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/07\/82f48153-3b70-41f1-b503-d1f8324c09fd.jpg","author_info":{"display_name":"importmanagerhub@sprylab.com","author_link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/author\/importmanagerhubsprylab-com\/"},"acf":{"readingTimeMinutes":"12","apple_news_title":""},"uagb_featured_image_src":{"full":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/07\/82f48153-3b70-41f1-b503-d1f8324c09fd.jpg",1448,2048,false],"thumbnail":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/07\/82f48153-3b70-41f1-b503-d1f8324c09fd-150x150.jpg",150,150,true],"medium":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/07\/82f48153-3b70-41f1-b503-d1f8324c09fd-212x300.jpg",212,300,true],"medium_large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/07\/82f48153-3b70-41f1-b503-d1f8324c09fd-768x1086.jpg",768,1086,true],"large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/07\/82f48153-3b70-41f1-b503-d1f8324c09fd-724x1024.jpg",724,1024,true],"1536x1536":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/07\/82f48153-3b70-41f1-b503-d1f8324c09fd-1086x1536.jpg",1086,1536,true],"2048x2048":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/07\/82f48153-3b70-41f1-b503-d1f8324c09fd.jpg",1448,2048,false]},"uagb_author_info":{"display_name":"importmanagerhub@sprylab.com","author_link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/author\/importmanagerhubsprylab-com\/"},"uagb_comment_info":0,"uagb_excerpt":"The common mistakes even experts make and how your next imaging session can be problem-free","_links":{"self":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts\/33702"}],"collection":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/users\/24"}],"replies":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/comments?post=33702"}],"version-history":[{"count":9,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts\/33702\/revisions"}],"predecessor-version":[{"id":34217,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts\/33702\/revisions\/34217"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media\/33688"}],"wp:attachment":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media?parent=33702"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/categories?post=33702"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/tags?post=33702"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}