For astrophotographers who use Photoshop, here's some interesting and some good news. A just-released plug-in called APF-R (Absolute Point of Focus) can do wonders for your images. Astrophotographer Christoph Kaltseis has developed APF-R in order to achieve high-resolution, ultra-sharp images that still look natural. As astro-imagers know, trying to sharpen point sources like stars can result in ugly halos and other unwanted artifacts.
This plug-in is based on some very complex algorithms that imagers have used for years, but using them was complicated and slow. Kaltseis has teamed with Picture Instruments to create a plug-in that can get you the same results at a reasonable price without all the anguish and complications. Instead of performing up to 50 steps manually in Photoshop and calculating radii with a calculator again and again, the plug-in automatically generates the first result after a few seconds. It uses the same technique and math that NASA and ESA imagers use on the Hubble photographs. Of course, it doesn't mean it will turn mundane images into Hubble-like images, but it can certainly sharpen good data into really good-looking data.
How You Use APF-R
You install the software, and it shows up under the Plug-ins Panel. I expected it under the Filters menu, where most of my plug-ins live, and I thought the installation had failed. You've been warned.
You start by making slight adjustments to the Radius control. You slide it to the right until the focus starts to break down. You can choose Fine or Extra Fine rendering, and it's recommended to try Extra Fine. You hit the Sharpen button and sit back for less than 30 seconds. You'll get a bunch of layers, which are iterations of the sharpening. When you turn them off, in most cases, you'll see your stars and other structures are sharpened, but the image itself is not damaged in any way that I could see. No star halos, no increase in noise. I can see why the Hubble imagers love this technique.
Don't expect big dramatic results. It will be subtle but solid. And in astro-imaging, subtle improvements are hard to get. The plug-in lets you compare the original to the APF-R result, and I think imagers will be happy with what APF-R provides. That's quite a good trick, and while the underlying math is likely different, it seems similar to the PSF (Point Spread Function) method I've tried many times, but the results aren't as good or as fast as they are with APF-R.
The plug-in is a reasonable $29 and can be purchased through the Adobe Marketplace, which is built into your Creative Cloud app. The app works with Windows and Mac versions of Photoshop. There are some tutorials here. I like the plug-in. It's improving my images.
One More Thing
I've found two other plug-ins I enjoy using for finishing astro images, and you may already have them. One is Topaz DeNoise AI. It's the best noise reduction software I've found for my nighttime images, which are inherently noisy. I think DeNoise AI works almost invisibly to remove the noise without losing focus. I also like and use the Topaz Sharpen AI tool. It's rescued or improved many of my images by sharpening them, particularly nebula images with many structures that can lose detail when stacking and combining. I don't think I would recommend it be used with APF-R because you might wind up at cross purposes. Most astro images will respond better to APF-R, especially images with a lot of stars, while images with a lot of structures like nebula should respond well to Topaz Sharpen AI. The Topaz tools are incidentally tools that work with astro images and in some cases work well. APF-R is purpose-built for astronomical images, and it really works well.