{"id":50893,"date":"2023-11-05T08:38:07","date_gmt":"2023-11-05T08:38:07","guid":{"rendered":"http:\/\/7da019fd-f7dd-4eb7-95b5-8ce3dffea5b5"},"modified":"2023-11-05T09:33:48","modified_gmt":"2023-11-05T09:33:48","slug":"how-to-improve-your-hydrogen-alpha-images-of-the-sun","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/rss_feed\/how-to-improve-your-hydrogen-alpha-images-of-the-sun\/","title":{"rendered":"How to improve your hydrogen alpha images of the Sun"},"content":{"rendered":"

Follow our image processing guide and capture better Ha images of the Sun. <\/p>

By Dave Eagle\n <\/p>

Published: Sunday, 05 November 2023 at 08:38 AM<\/p>

\n\n

In this guide we’ll reveal how to improve hydrogen alpha images of the Sun.<\/p>

When using a hydrogen-alpha (Ha) telescope or filter, we view a layer above the Sun\u2019s white-light photosphere called the chromosphere.<\/p>

The features that are revealed in Ha, like sunspots, prominences and filaments, can be very active, often changing extremely quickly.<\/p>

The Sun becomes a living, breathing and very exciting star, and is amazing to watch and image in fantastic detail.<\/p>

Read our guides on how to safely photograph the Sun<\/a> and how to photograph solar activity<\/a><\/em><\/strong><\/p>

Before: Our original stacked hydrogen-alpha image of an active region of the Sun\u2019s chromosphere. After: the final version after processing with AstroSurface and Affinity Photo to sharpen it, brighten the huge filament and prominences, and introduce vibrant colour. Credit: Dave Eagle<\/figcaption><\/figure>
It\u2019s important to emphasise that, of course, any observing or imaging of the Sun should always be done with the correct safety filters in place.<\/p>
Taking images of the Sun is akin to planetary imaging.<\/p>
A camera, using video-capture software, captures a video composed of hundreds of individual frames. <\/p>
This is stacked using video-stacking software (AutoStakkert!, RegiStax or AstroSurface, for example) to produce a single image.<\/p>
The resulting combined image contains much less noise and has enhanced subtle detail, but this does need to be teased out using a combination of tools in AstroSurface and Affinity Photo.<\/p>
I\u2019m going to take you through the processes involved so that with a bit of image processing, you can improve your hydrogen alpha images of the Sun.<\/p>
**Sharpen your h-alpha images of the Sun<\/strong><\/h2>**
$\"Improve$
Credit: Dave Eagle<\/figcaption><\/figure>
Our first step is to quickly pre-sharpen the image to reveal additional fine detail. <\/p>
Open AstroSurface and load your stacked image from the folder you saved it in. <\/p>
Once opened, select ***Filters > Wavelets-Deconvolution<\/em><\/strong> from the menu (see image above).<\/p>***
If ***Use (ROI)<\/em><\/strong> is displayed at the top right of the tool window that pops up, using the mouse draw a square around a part of your image to see the effect as the tool is adjusted.<\/p>***
The tool remembers the last setting used. Click ***Reset<\/em><\/strong> to start afresh.<\/p>***
Start with the top ***Wavelets HF<\/em><\/strong> slider (labelled in the program as \u20183\u2019), moving it a small amount to the right.<\/p>***
A small adjustment gives a nice sharpening to the image, but if noise appears move the bottom ***Wavelets HF<\/em><\/strong> slider slightly to the left.<\/p>***
If more noise reduction is needed, the ***Noise Prefilter<\/em><\/strong> slider (labelled \u20181\u2019) can be moved to the right.<\/p>***
Once you\u2019re happy with the result, click Do All<\/em><\/strong> (if ROI was used), then ***Ok<\/em><\/strong>.<\/p>***
***Don\u2019t be afraid to repeat this step, resetting the tool and using smaller adjustments if required.<\/p>***
***Save this image using a different name so that the original image is not overwritten.<\/p>***
**Using Affinity Photo<\/strong><\/h2>**
$\"Improve$
Credit: Dave Eagle<\/figcaption><\/figure>
Next we turn to Affinity Photo. Open your pre-sharpened image.<\/p>
In my image, prominences could be seen at the top limb, but they were quite faint.<\/p>
To brighten features like this, select ***Layer > New Live Filter Layer > Shadows\/Highlights<\/em><\/strong> (see image above).<\/p>***
Slide the top two sliders differing amounts to the right to brighten the prominences, then click ***Merge<\/em><\/strong>.<\/p>***
Now we can apply a little more sharpening to the image using ***Live Filter Layer<\/em><\/strong>.<\/p>***
Click ***Layer > New Live Filter Layer > Sharpen > Clarity<\/em><\/strong>.<\/p>***
Move the slider to the right to apply gentle sharpening. Continue until you\u2019re happy with the adjustment, then click ***Merge<\/em><\/strong> to finish the process.<\/p>***
**Adding colour<\/strong><\/h2>** $\"Improve$
Credit: Dave Eagle<\/figcaption><\/figure>
Although the Sun is white, everyone loves to see images of the Sun as orange.<\/p>
So, part of the process to improve your hydrogen alpha images of the Sun is to add a bit of colour.<\/p>
You can find out more about this in our guide on how to colourise astrophotos of the Sun<\/a>.<\/p>
First we need to check and possibly change the document type.<\/p>
Select ***Document > Convert Format\/ICC Profile<\/em><\/strong>.<\/p>***
The image type should be RGB\/16<\/em><\/strong>. If the image file is a different format, select RGB\/16<\/em><\/strong> from the dropdown menu and click ***Convert<\/em><\/strong>.<\/p>***
Now open the ***Curves<\/em><\/strong> adjustment tool.<\/p>***
In the window that opens (shown in the image above), below the histogram where it says Master<\/em><\/strong>, select ***Blue<\/em><\/strong> from the dropdown list.<\/p>***
***Grab the middle of the blue line on the histogram and drag it as far down to the bottom right-hand side of the histogram as possible.<\/p>***
Then select ***Red<\/em><\/strong> from the dropdown list and slightly drag the red line up, making a gentle curve above the diagonal white line.<\/p>***
Switching to ***Green<\/em><\/strong>, drag the line to curve slightly below the white line. The Sun should now be orange. <\/p>***
Click ***Merge<\/em><\/strong>.<\/p>***
Finally, use the crop tool to cut out the edges of the image to remove stacking artefacts, then save the file as a new image (***File > Export<\/em><\/strong>).<\/p>***
***Below you can see how my final processed image turned out.<\/p>***
***$\"Hydrogen$*** Hydrogen alpha image of the Sun. Credit: Dave Eagle<\/figcaption><\/figure>
3 quick tips<\/strong><\/h2>
Improve your hydrogen alpha images of the Sun with these 3 tips.<\/p>
Wavelets LF\u2019 and \u2018Deconvolution Richardson-Lucy\u2019 adjustments in AstroSurface can be used to further improve the sharpness in good-quality images.<\/li>
Treat sharpening with caution. Over-sharpening causes unwanted artefacts. Small, gentle adjustments are always best.<\/li>
Save your workflow as an adjustment preset or a macro to perform elaborate changes with just a single click.<\/li><\/ol>
***Have you captured an image of the Sun?*** ***Don’t forget to send us your images<\/a>!<\/em><\/strong><\/p>***
***This guide originally appeared in the November 2023 issue of BBC Sky at Night Magazine.<\/em><\/strong><\/p> <\/body><\/html>\n***
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