Expert processing tips to enhance your astrophotos <\/p>\n\n
ASTROPHOTOGRAPHY<\/span><\/h5>\n\n
PROCESSING<\/span><\/h2>\n\n\n\n
APY Masterclass Capturing Venus and the Moon <\/h2>\n\n
Lighting Venus\u2019s crescent and the lunar limb evenly is no small feat <\/p>\n\n
The final shortlisted APY 2021 image: Beyond the Limb <\/figcaption><\/figure><\/div>\n\n
<\/figure><\/div>\n\n
Ever since I first became interested in astronomy, I have been fascinated by the iconic images of Earth rising above the lunar horizon from the Apollo missions. When I realised that the Moon\u2019s occultation of Venus, visible on 19 June 2020, would give me the opportunity to capture a similar image for myself, it immediately became one of my astrophotography aims of that year. I decided to capture the event with a very narrow field of view in order to enhance the \u2018crescent over lunar horizon\u2019 feeling and I also wanted to capture the event in colour to record the daylight blue sky. To achieve this, I used my Celestron C11 equipped with a colour planetary camera at prime focus.<\/span><\/p>\n\n
In order to achieve a natural look to the image, I chose short exposures so as not to oversaturate bright Venus. This made the crescent Moon\u2019s limb barely visible in the shots (see image, right). To compensate for this low contrast I had my planetary camera\u2019s gain set to zero, so the noise in individual frames would be as low as possible. Unfortunately, some low cloud moved in during the capture a few seconds after the Moon began to hide Venus, and obscured the scene. When the sky was blue again, Venus had totally disappeared, so I took more shots of the Moon, this time with longer exposures to better reveal the details of the lunar limb.<\/span><\/p>\n\n
The initial capture, with Venus in view and a very faint lunar limb <\/figcaption><\/figure><\/div>\n\n
Stacking Venus <\/strong><\/h4>\n\n
For the processing, I started with AutoStakkert! to extract frames for stacking from the video captures and to improve image quality and sharpness. Stacking the bright Venus frames was straightforward, but for the Moon data the software wasn\u2019t able to correctly align the frames due to their low contrast. I had to export these frames, preprocess them to improve contrast, and then reload them into AutoStakkert! so that the program would correctly align and average the frames (see Screenshot 1). After this, I used PixInsight to sharpen the averaged images of Venus and the Moon, using tools including deconvolution and wavelets.<\/span><\/p>\n\n
Screenshot 1: stacking the preprocessed lunar images in AutoStakkert! <\/figcaption><\/figure><\/div>\n\n
Screenshot 2: compositing Venus, lunar and blue sky images with PixInsight <\/figcaption><\/figure><\/div>\n\n
Screenshot 3: adding an enhanced lunar image layer <\/figcaption><\/figure><\/div>\n\n
I took care not to over-enhance the details, which would ruin the natural appearance I was looking for in the final image, and made sure that the final sharpness of Venus and the Moon was similar in order to avoid discrepancies in the final composite. Then I positioned the sharpened images of Venus and the Moon using a frame that corresponded to the beginning of the occultation. I chose a frame in<\/span> which the crescent of Venus was not hidden by the Moon to avoid having to manage the fact the Moon was hiding some part of the planet. I also created a background image with the RGB values of the blue sky I had extracted from the captures.<\/p>\n\n
<\/p>\n\n
<\/div>
\n
3 QUICK TIPS <\/h4>\n\n\n\n
1. <\/strong>Have several scopes and cameras that can be used in multiple combinations and adapted to different subjects. <\/p>\n\n\n\n
2. <\/strong>To obtain a natural aspect to the final image, avoid over-enhancing or over-smoothing to ensure image consistency. <\/p>\n\n\n\n
3. <\/strong>Flip your image left\/right during processing to see it with a new eye for a few seconds. <\/p>\n<\/div><\/section>\n\n
Blending insight <\/strong><\/h4>\n\n
I now had three images of the exact same size: one of the Moon and one of Venus matching the instant before the beginning of the occultation and one of the blue sky background that I had to blend to get the final image. Rather than simply overlaying the images, I used PixInsight to blend them. I added the three images to the program using the Pixel Math function, with the right coefficient corresponding to the actual brightness of the three images (see Screenshot 2). From this, I generated several outputs with either full background or partial reduction of the background, to help with the visibility of the lunar details. Where possible, I preferred to blend first, then stretch the image, staying close to the actual light intensities to avoid introducing an unnatural appearance. <\/p>\n\n
I used Photoshop for the final adjustments. Here I adjusted the image curves to improve the visibility of the Moon and used hue and saturation to alter the colour of the background. Despite this, I found that the Moon was still not visible enough to convey the feeling I was looking for in the final image, so I slightly increased its visibility using my enhanced Moon image as a layer (see Screenshot 3). I had to keep this enhancement subtle, otherwise it quickly showed the noise in the Moon image, which gave an unnatural look. <\/p>\n\n
However, I ended up deliberately adding some noise into the image to give some texture to the uniform blue background and slightly reframed it to get the view of the Venus crescent hovering above the lunar horizon, which I had been dreaming of. This became the final \u2018Beyond the Limb\u2019 image that was shortlisted for APY 2021.<\/p>\n\n
<\/p>\n\n
\n\n
<\/figure><\/div>\n\n
Nicholas Lefaudeux is an optical engineer and amateur photographer. He has been awarded an APY in different categories in 2018, 2020 and 2021<\/p>\n\n
<\/p>\n\n
Photos: NICHOLAS LEFAUDEUX<\/p>\n","protected":false},"excerpt":{"rendered":"
Lighting Venus\u2019s crescent and the lunar limb evenly is no small feat<\/p>\n","protected":false},"author":24,"featured_media":33752,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"ub_ctt_via":"","purple_page_number":"78","purple_custom_meta_purple_page_number":"78","purple_seq_number":"1","purple_custom_meta_purple_seq_number":"1","purple_source_article":"article_78-1.xml","purple_custom_meta_purple_source_article":"article_78-1.xml","purple_source_issue":"August-2022","purple_custom_meta_purple_source_issue":"August-2022","purple_external_id":"August-2022-78-1","purple_custom_meta_purple_external_id":"August-2022-78-1","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":[34],"tags":[14],"featured_image_src":"https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/07\/33f8a4b7-fa80-4766-bcdc-8218995c4c38.jpg","author_info":{"display_name":"importmanagerhub@sprylab.com","author_link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/author\/importmanagerhubsprylab-com\/"},"acf":{"readingTimeMinutes":"5","apple_news_title":""},"uagb_featured_image_src":{"full":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/07\/33f8a4b7-fa80-4766-bcdc-8218995c4c38.jpg",1396,993,false],"thumbnail":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/07\/33f8a4b7-fa80-4766-bcdc-8218995c4c38-150x150.jpg",150,150,true],"medium":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/07\/33f8a4b7-fa80-4766-bcdc-8218995c4c38-300x213.jpg",300,213,true],"medium_large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/07\/33f8a4b7-fa80-4766-bcdc-8218995c4c38-768x546.jpg",768,546,true],"large":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/07\/33f8a4b7-fa80-4766-bcdc-8218995c4c38-1024x728.jpg",800,569,true],"1536x1536":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/07\/33f8a4b7-fa80-4766-bcdc-8218995c4c38.jpg",1396,993,false],"2048x2048":["https:\/\/c01.purpledshub.com\/uploads\/sites\/77\/2022\/07\/33f8a4b7-fa80-4766-bcdc-8218995c4c38.jpg",1396,993,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":"Lighting Venus\u2019s crescent and the lunar limb evenly is no small feat","_links":{"self":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts\/33759"}],"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=33759"}],"version-history":[{"count":8,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts\/33759\/revisions"}],"predecessor-version":[{"id":35670,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/posts\/33759\/revisions\/35670"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media\/33752"}],"wp:attachment":[{"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/media?parent=33759"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/categories?post=33759"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/wp-json\/wp\/v2\/tags?post=33759"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
![\"\"](\"https:\/\/dj9jqhxgw9833.cloudfront.net\/uploads\/sites\/77\/2022\/07\/final-image_preview-1024x719.jpg\")
![\"\"](\"https:\/\/dj9jqhxgw9833.cloudfront.net\/uploads\/sites\/77\/2022\/07\/00549d93-c447-4a1d-b2ea-2e2466fbe3c9.jpg\")
<\/figure><\/div>\n\n![\"\"](\"https:\/\/dj9jqhxgw9833.cloudfront.net\/uploads\/sites\/77\/2022\/07\/screenshot-1_preview-1024x767.jpg\")
![\"\"](\"https:\/\/dj9jqhxgw9833.cloudfront.net\/uploads\/sites\/77\/2022\/07\/1b733490-c6ec-4002-a04b-903a438b729e.jpg\")
![\"\"](\"https:\/\/dj9jqhxgw9833.cloudfront.net\/uploads\/sites\/77\/2022\/07\/9b1a12d3-5bfa-4ea6-a09e-5b945beee54b.jpg\")
![\"\"](\"https:\/\/dj9jqhxgw9833.cloudfront.net\/uploads\/sites\/77\/2022\/07\/b84cd907-9061-4372-bdf9-da60a4d0cf54.jpg\")
![\"\"](\"https:\/\/dj9jqhxgw9833.cloudfront.net\/uploads\/sites\/77\/2022\/07\/5de51ac6-c788-4f76-8263-da41e40776ac.jpg\")
<\/figure><\/div>\n\n