To stack, or not to stack? Most astrophotographers will agree it’s necessity with deep sky images, but is it really necessary for lunar imaging when the moon is so big and bright in the sky? There are a lot of single frame photos of the moon that show incredible detail, so is it really worthwhile going through the process of taking dozens, or even hundreds or thousands of images and then stacking them? Are the results really that visible? In this article, I we’ll go through the process of stacking a lunar image and see the results at each step along the way.

WHAT IS STACKING?

Stacking is a very familiar process to most astrophotographers. Unlike the days of film, there are no longer single 30+ minute exposures of celestial objects taken. These days, several shorter exposure are stacked together to create a final image.

Starry Sky Stacker. Deep Sky Stacker Commercial, $24.99 Mac OS X. Starry Sky Stacker. Fast; Easy to use; Cons. Mac Os X only; Does not read RAW files; Basic; Starry Sky Stacker is Starry Landscape Stacker brother and it has been created to stack deep sky astrophotography images. DeepSkyStacker is a freeware for astrophotographers that simplifies all the pre-processing steps of deep sky pictures. Simple post-stacking processes to quickly view the final result. Saving the resulting image to a TIFF or FITS file (16 or 32 bit). RegiStax 6, available as a free download, is one of the most powerful and widely used programs for planetary imaging techniques including sorting, registering, stacking, and sharpening webcam images. Sean Walker described its key functions in his review of version 3 in the December 2005 issue, page 94.

Feb 06, 2020 Without stacking, the noise in the image can become a problem with histogram stretching. Sometimes the Deep Sky Object (DSO) is so faint that only a few photons arrive at your camera during a single exposure. In this scenario, stacking images will increase the number of captured photons for very dim objects.

Stacking – whether for deep sky or solar system – is the process of taking multiple images of the same object and digitally combining the images to increase the signal to noise ratio. With each additional stacked image, more signal is added to the final image while background noise is reduced. Those process of stacking deep sky and solar system images is completely different, but the end goal is the same – to bring out as much fine detail in an image while cancelling out digital noise.

This article will be focusing on lunar stacking. In this case, I won’t be covering the fine details of how to use each and every program used in the process, but will talk about the basic workflow that applies to any software you do this with.

THE PROCESS

These are the major steps involved in processing a solar system image. The mechanics of processing the moon, sun, or planets vary slightly in process and equipment, but they all contain these steps. There are different software programs that take care of each step, each requiring its own unique processes, but these are the main steps required.

Acquisition
Pre-processing
Stacking
Sharpening
Post-processing.

Acquisition

It all starts with taking your pictures. Solar system imaging is generally done with a dedicated webcam type camera attached to a telescope instead of a DSLR, and the camera shoots video instead of still frames. Since solar system objects are very bright compared to deep space objects, exposures of more than a few fractions of a second will blow them out completely. These webcams will typically shoot exposures of 30 to 100 frames per second, or 1/30th to 1/100th of a second. Generally, this is also the method used with a DSLR. The camera is set to capture high frame rate / low resolution video like 30-60 fps at 640 x 480 resolution. Planets are so small that they are still tiny in the field of view at that resolution. Planetary imaging is very difficult with a DSLR at prime focus and generally not recommended.

The moon, however, is a much bigger target. Using such a webcam results in very high magnification views of the moon. Craters will be seen in astounding detail, but if you wish to see the entire moon, a DSLR is the only way to go unless you want to take potentially dozens of videos, stack them into images and then create a full panorama of the moon.

For this lunar image, I used a Nikon D5100 attached to an Explore Scientific 80ED apochromatic telescope mounted on a Celestron Advanced VX mount. Tracking isn’t necessarily required to shoot the moon. You can also shoot the moon easily with a 300+mm lens on a stationary tripod. Since you won’t be tracking, you’ll have to manually readjust your framing from time to time to keep the moon in your field of view. You can also shoot the moon with a manually tracked telescope on any type of mount. Once again, you’ll need to readjust your framing every so often to keep the moon in frame.

For this project, I shot 470 images of the moon. My camera was set at ISO 100 with exposures of 1/160 of a second. I also shot 10 dark frames (images shot at the same setting but with lens cap on) to reduce noise. I could easily have also shot HD video of the moon at 30 fps with the same exposure settings and used the resulting video to process in the next step. Or for faster acquisition, I could have used my D750 at 60 fps. The end result would have been the same.

This is the RAW file as it came off the camera converted to JPG without any editing. The moon occupies a rather small space near the centre of the frame. It’s quite bright and very detailed. Many people would proudly share such an image online with little to no other post-processing and be quite happy with it. And rightfully so too. It’s a great image with sharp focus and good brightness. But with some processing work, we can do much better than this.

NOTE: If you’re using a DSLR, make sure to always shoot in RAW mode and never in JPG. And if you’re not dealing with video files, use TIFF as your intermediary format and only save out a JPG at the very end for your final image to share online. You want to maintain the highest possible quality through your workflow.

Original, unprocessed RAW image converted straight to JPG.

But zooming in on said image and examining it closer, fine detail shows that there is some visible pixellation and noise. Fine details such as craters are a bit blurry due to atmospheric distortion. And since the moon is so bright due to its advanced waxing gibbous stage, there’s very little contrast between light and dark areas.

Heavy zoom showing pixellated detail and noise.

Pre-Processing

The first step to preparing your images is to align your frames, crop them to size, and normalize the brightness. When shooting with a tracker or equatorial mount, alignment isn’t as critical. If your polar alignment and tracking are accurate, your target should be in the centre of the field of view throughout the entire series of images. However, if you were shooting full resolution stills instead of a video, you’ll see that the moon is but a small object in the centre of your image covering an area of anywhere from 800 x 800 to 1000 x 1000 pixels. Processing full 10+ MP still photos will take a LONG time, so this pre-processing step will save you a lot of time.

Not that even when shooting HD video at 1920 x 1080, you’ll still have a lot of black space on either side of your target. Pre-processing will remove this dead space making for much faster alignment and stacking.

For pre-processing, I use PIPP – Planetary Imaging PreProcessor. This free program is available for Windows, Linux and MacOS and I highly recommend it to anyone shooting and stacking images of solar system objects.

I loaded my images and my dark frames in their respective spots under the Source Files tab in PIPP. Since I put in a series of images, it automatically selected Join Mode since these are all pics of a single object. And I also selected the Solar/Lunar Full Disc under the Optimise Options For section. This is pretty self-explanatory.

From the Processing Options tab, I chose to stretch the histogram to 75% and set the black point to 0%. This reduced the overall image brightness a bit and ensured that all my different frames were at the exact same brightness and set my background to black. In this tab, I also chose to crop the image to 1200 x 1200. This left me the moon nicely framed with a bit of space around it.

From the Quality Options tab, I selected Enable Quality Estimation and Reorder Frames in Quality Order check boxes This will order the images from highest to lowest quality for later stacking.

From the Output Options tab, I chose the output format to be TIFF, which saves a series of TIFF files. AVI output is the default option and is perfect for lower resolution final images or 640 x 480 video, But I find larger video files sometimes don’t play nice with other stacking software, so I prefer saving images taken with my DSLR as TIFF. But either way should work.

Then finally, I ran the whole process. And this is the resulting image. This is just a single out of 470 frames that was exported from PIPP. The moon is nicely centred and the brightness neutralized. This will be the series of images that will imported in the next step for stacking.

Original shot – 16 MP RAW file converted to TIFF and cropped to 1200 x 1200

Examining this zoomed-in section, you can see that the noise and pixellation that visible in the previous stage is gone. PIPP performed the dark frame subtraction from each individual image lowering noise levels significantly, It looks far smoother than the previous stage. Detail is still fuzzy and not very sharp, but the pixellation caused by the noise has been removed.

Heavy zoom showing smoothed detail and no noise

Stacking

Next comes the process of stacking the individual frames. There are several free programs for Windows, but I’m not personally aware of any available for Mac. There is a long, more painful way of doing this in Photoshop, but it’s very time-consuming and the steps are way beyond the scope of this article.

The 2 leading free programs used are Registax6 (RS6) and AutoStakkert!2 (AS2). RS6 is a favourite of many because it does both the stacking and sharpening stage. It’s basically an all-in-one tool for your solar system processeing, whereas AS2 only stacks. But more on sharpening later.

When stacking, the software will analyze each frame for quality. Since all my shots were of exceptional quality (all rated 98%+ in PiPP), I told AS2 to stack the top 90%, for a total of 414 frames.
This is the resulting image with everything stacked. Looking at the full image of the moon, you see it’s brighter than a single source frame. It’s completely smoothed out, is noise-free, and small details that were fuzzy and still pixellated in the last step are showing fine detail that wasn’t visible before.

400 stacked frames

At this stage, the fine detail still looks a little fuzzy, but you can see that there’s no noise, and fine detail that wasn’t visible in the original pre-processed image is now visible, albeit a little blurred. The image now needs to be sharpened to bring that fine detail into focus.

Zoomed in view of stacked image.

Sharpening

Sharpening is the act of deconvolution an image to deblur it. There are a couple of ways this can be done. This most common method is through wavelet sharpening using RS6. The other is using a deconvolution filter.

As I mentioned earlier, RS6 is the best free option out there for this process, which makes it a good all-in-one package. You can go right into sharpening after stacking. Or alternately, you can import an image file that was stacked in another program for wavelet sharpening. I won’t go into details on the mechanics of using RS6. There are lots of videos on YouTube that can explain how it works far better than I can. But this will be the method that most people will use.

For deconvolution, there are no free options that I’m aware of. I use Astra Image. which costs $29.95 US. And there are some paid Photoshop plugins that will do this as well. I can’t recommend any of them, as I haven’t used them personally.

For this image, I opened my stacked image in Astra Image and ran the Deconvolution for Sharpening filter, From this, I chose the Lucy-Richardson Deconvolution and adjusted it accordingly, And this was the result. On this large scale, you can see fine details in the surface that weren’t visible at any of the previous stages. Large structures like craters, peaks and valleys are clearly visible. There’s far more visible relief on the surface detail than you could see before.

Stacked image deconvoluted in Astra Image

The same area zoomed in shows incredibly fine detail. Small rilles and craters are clearly visible. crater Clavius and its smaller craters pop out distinctly. The ridge on the edge of Tycho is clear and sharp. The image is clear, crisp and noise-free. At this point, all that’s left is final cosmetic touch-ups in Photoshop.

Post-processing

This is where the final touch-ups are made in terms of colour, brightnesses and balance. This last step is where some artistic licence comes in. This can be done in Photoshop, Lightroom, or whatever other software you normally use.

For this, I opened the my file in Photoshop CC and opened up Camera Raw. I made the appropriate adjustments to exposure, contrast, highlights and shadows, to my personal taste just as I would do in Lightroom and applied my DAA watermark. And the final image is now complete.

Final image with some correction in Photoshop.

And as you can see in this same section zoomed in on the final image, the details just jump out. The contrast between light and dark areas is much more distinct. Small craters everywhere stand out. Ejecta lines that were washed out in the source images show up in clear detail.

THE RESULTS

So I think the original question has been answered. Stacking is definitely worth it on lunar images shot with a DSLR. Regardless how good your camera, equipment or technique is, you can’t match the results of a stacked image in a single frame. Sure, you can get some great single images of the moon, but you just can’t compete with a well processed, stacked image in terms of fine detail.

Hopefully this will be of help to aspiring astrophotographers who want to take great shots of the moon.

And as always, clear skies, and keep those eyes and lenses pointed up!

Adobe premiere pro cc shortcuts mac. Post-processing astrophotography images is mandatory: you cannot avoid it. It can be a fairly long and technical process, but it is necessary to squeeze out the most you can from your images.

Everything begins with pre-processing your images, a step including image calibration and image stacking, which we have already covered in this article.

After that, it is time to post-process your stacked image with your software of choice. In this article, we will discuss the different options that are available to post-process your astrophotography images.

Note: Don’t miss the detailed video at the end of this article, It was created to help show you how to process your images with some of the software mentioned in this article.
Click here to skip to our Image Processing Demo Video.

What Does Post-Processing Mean In Astrophotography?

In astrophotography, the post-processing includes steps that are crucial to the quality of the final image. Those steps can be summarized as:

• Histogram stretching
• Gradients and light pollution removal
• Stars color calibration
• Stars reduction and Stars removal
• Sharpening and noise reduction
• Final tweaks

Of the steps mentioned above, it is worth to spend a few words on the Histogram Stretching, as it is of utmost importance in deep-sky astrophotography.

What Histogram Stretching Is And Why You Need It

With image stacking, you have combined all your light frames (the actual images of the sky) into a single image with an enhanced signal-to-noise ratio.

With deep sky astrophotography, this stacked image can be surprisingly dark, with only a few bright stars visible.

There is nothing wrong with it, as all the details and information are there, but hidden in the dark background. And this is why this process also goes under the name of background extraction.

Histogram stretching can be done manually using Adobe Photoshop or in automatic/semi-automatic way using astrophotography software such as Astro Pixel Processor, Star Tools, or His Majesty PixInsight.

A rigorous explanation on how digital data are recorded and how the histogram works can become fairly technical and is beyond the scope of this article.

To keep it simple, let’s say that when you perform the stretching of the histogram, you are broadening the histogram. Thus pushing details that were crammed in the blacks towards the middle tones.

And you do that slowly, in small steps, to ensure retaining the best possible image quality.

The process allows us to take full advantage of the image stacking process, and it results in a cleaner, brighter image with a lot of details that were not visible (or barely visible) in the single exposures.

Stars Reduction / Stars Removal

Star reduction is another process that is standard when editing deep-sky astrophotography.

While it seems odd that you want to shrink or remove stars from a photo about stars, this process aims to make the multitude of visible stars in the image less imposing and distracting.

By reducing enlarged stars due to the histogram stretching and by removing the smallest stars, you make the deep sky objects in the image more visible, as shown in the image below.

The procedure is particularly useful when shooting deep-sky objects, such as nebulae, that are in the Milky Way Band.

Software For Astrophotography Post-Processing

We can group the software for astrophotography post-processing in two categories:

1. generic photo editors, such as Photoshop, Gimp, Affinity Photo, etc.
2. Astrophotography editors, such as StarTools, Nebulosity, Astro Pixel Processor, Pixinsight, etc.

The main advantage of generic photo editors over specific astrophotography editors is versatility.

With a generic photo editor, it is easy to post-process all kinds of astrophotography, from deep-sky imaging to lunar and planetary shots, passing for star trails and starry landscapes.

In this article, for example, we discussed how to stack starry landscape images in Photoshop.

Not many astrophotography editors are this flexible.

Here is a list of software that are most commonly used to post-process astrophotography images.

Adobe Lightroom CC

Generic Photo Editor | Commercial From $9.99 Subscription Plan | Windows, Mac OS X, IOS

Pros

• Easy to use
• Powerful image development and image organizer
• Easy integration with Photoshop
• Can use photographic plugins

Cons

• Can’t do the complex editing needed for astrophotography (histogram stretching, Stars Reduction, etc)
• Limited to cosmetic tweaks

Adobe Lightroom is a popular, easy to use and fairly powerful RAW developer and image organizer.

Its usefulness in astrophotography is somewhat limited, as you cannot perform complex tasks such as histogram stretching, advanced light pollution, and gradient removal, star reduction, etc.

On the other hand, it is a terrific editor for the final cosmetic tweaks to your image and to organize them in collections, per tag, and location. Lightroom is also great for color proofing your images before printing them.

If you are subscribing to the Adobe Photography Plan, you also have Photoshop CC included for free. And here is where things get interesting.

To get the best from the two worlds, load your stacked images in Lightroom, organize them in collections, and call Photoshop from within Lightroom for the astro-specific editing (histogram stretching, etc.).

Then make the final tweaks in Lightroom.

Adobe Photoshop CC

Generic Photo Editor | Commercial From $9.99 Subscription Plan | Windows, Mac OS X, IOS

Pros

• Versatile and Powerful Photo Editor / Image Manipulation Software
• Suitable for deep sky and planetary astrophotography as well as star trails and starry landscapes
• Astrophotography Action Sets and Plugins Available
• Subscription Plan with Photography Bundle

Cons

• Lacks Some Advanced Features for Astrophotography

Photoshop is one of the most commonly used software in the field of photography editing and image manipulation, and it can be used to post-process astrophotography work.

If you are a beginner astrophotographer, you are on a tight budget or you already own Photoshop, you should give it a try as all the basic post-processing steps can be performed in this software.

If you need more advanced features, you can also expand Photoshop capabilities thanks to many astrophotography related Action Sets, Plugins, and Panels.

Finally, with Camera Raw filter and other photographic plugins (like for smart sharpening and advance noise reduction), you can perform with ease all the final tweaks an image may need.

As a Photoshop user, I tried many plugins and action sets for astrophotography, and here is my must-have extensions list.

Astronomy Tools by ProDigital

Actions Pack For Deep Sky Astrophotography| Commercial $21.95 | Windows, Mac OS X

A rich set of actions suitable for post-processing astrophotography images. The set includes actions such as star reduction, enhanced DSO, light pollution and color gradient removal, sharpening, and noise reduction.

Photokemi’s Star Tools by Ken Mitchel

Actions Pack For Deep Sky Astrophotography | Commercial $14.95 | Windows, Mac OSX

Similarly to Astronomy Tools, this action set is most useful for deep space astrophotography.

It offers advanced star removal and star reducing actions, semi-automatic histogram stretching, different sharpening and noise reduction actions, as well as actions such as nebula filters and star color enhancement.

There is also a set of extra actions, available for $6.95. Mario multiverse download mac.

GradientXterminator by Russell Croman

Plugin For Deep Sky Astrophotography | Commercial $49.95 | Windows, Mac OS X

This plugin is a gradient removal tool that is easy to use and extremely effective. Despite a rather steep price (a trial is available for you to test the plugin), this is a terrific add-on for Photoshop, if you are serious about deep-sky astrophotography.

Hasta La Vista Green! (HLVG) by Regelio Bernard Andreo

Plugin For Deep Sky Astrophotography | Donationware | Windows

Despite its old age, this plugin is still useful, and it does an excellent job of removing green noise and the green casts such noise may cause in some images.

Astro Panel By Angelo Perrone

Panel For Starry Landscape And Deep Sky Astrophotography | Commercial | Windows, Mac OS X

Astro Panel consists of a rich set of functions and methods that produce high quality starry landscapes and Milky Way images.

It is also easy to process Deep Sky Photos thanks to advanced functions for reducing digital noise and hot-pixels, eliminating the gradient, managing artificial flat, and much more …

Furthermore, astronomical images aside, you can use the Astro Panel to edit classic landscape images too.

Affinity Photo

Generic Photo Editor | Commercial $49.99 | Windows, Mac OS X, IOS ($19.99)

Pros

• Affordable
• Powerful
• The interface and commands are similar to Photoshop for an easy switch
• Suitable for deep sky and planetary astrophotography as well as star trails and starry landscapes

Cons

• Lacks third-party actions sets, plugins and panels

Affinity Photo from Serif Lab is a great, affordable alternative to Photoshop, and you do not need to pay for a subscription plan.

With Affinity Photo, you can carry out with ease all of the basic astrophotography post-processing.

But since there are no plugins, action sets, and panels to help you out, you have to learn to do things manually, even the more advanced tasks such as star reduction.

Gimp

Photo Editor | Freeware | Windows, Mac OS X, Linux

Pros

• Freeware
• Great community and lot of info available
• Powerful
• Suitable for deep sky and planetary astrophotography as well as star trails and starry landscapes

Cons

• Interface a bit confused
• Lacks third-party actions sets, plugins and panels

Deep Sky Stacking Programs For Mac Pro

Gimp is the historical freeware alternative to Photoshop. Since it is freeware and on the market for many years, there is a big community of users, so it is easy to find relevant tutorials and guides to help you out.

The software has a slightly confusing interface, particularly if you are trying to switch from Photoshop, but it is powerful enough to let you edit your astrophotography images with ease.

Unfortunately, there are no third-party action sets, plugins, or panels to help you automate some tasks. As with Affinity Photo, you have to learn how to do everything manually.

Star Tools

Astrophotography Post-Processing Tools | Commercial $45 | Windows, Mac OS X, Linux

Pros

• Affordable
• Multiplatform
• Offers many advanced tools
• Trial without time limit

Cons

• Interface bit confusing
• Convoluted workflow
• Slower than other software

StarTools is a deep-sky post-process editor that does everything you need except the initial light frame calibration and stacking.

Once you have the stacked image from, say, Deep Sky Stacker, you can post-process it in StarTools, taking advantage of the many tools the software has to offer.

The interface is a bit confusing, and it may take a while to get used to the convoluted editing workflow.

Fortunately, the trial version never expires, so you can take all the time you need to experiment with StarTools before deciding if it is for you or not. The only limitation of the trial is that you cannot save your results.

SiriL

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Multipurpose Astrophotography Editor | Freeware | Windows, Mac OS X, Linux

Pros

• Freeware
• Multiplatform
• Active Development
• Suitable for different kinds of astrophotography
• Fairly easy to use
• Powerful full-grown astrophotography software

Cons

• Develop the image is a lengthy process
• Interface a bit confused

I’m no expert with SiriL, but it is probably the only full-grown astrophotography editor that is freeware and multiplatform.

Siril will allow you to perform all the essential steps in your astrophotography editing workflow, from image calibration and stacking to (manual or auto) histogram stretching and post-processing.

Since it is free, if you are looking for an astrophotography package, SirilL is worth downloading and having a go with it.

Nebulosity

Deep Sky Astrophotography Editor | Commercial $95 | Windows, Mac OS X

Pros

• Capable full astrophotography editor
• Can calibrate and stack your images
• It offers many advanced tools

Cons

• Not abandonware, but development is somehow slow
• The interface feels old and not very user friendly

Nebulosity 4 was my first software specific to astrophotography. It is intended for deep sky astrophotography and is fairly easy to use.

It offers a good way to calibrate and stack your images, and you can use it for stretching the histogram, tighten the stars, calibrate the background colors, and perform sharpening and noise reduction.

But the interface is not as intuitive, it looks “old,” and while development is there, it is not as quick compared with other software.

Astro Pixel Processor

Deep Sky Astrophotography Editor | Commercial €60/Yr (Renter’s License) Or €150 (Owner’s Renter) | Windows, Mac OS X, Linux

Pro

• Great deep sky astrophotography package
• Powerful
• Easy to use
• Batch processing
• 30-days free trial available
• Suitable for creating stunning mosaic with ease
• Active development
• Rental license available

Cons

• Vignetting removal tool could be better
• No Stars Reduction methods available

Astro Pixel Processor is my goto software for my deep sky astrophotography and I decided to go with the renter’s license to always work with the latest version of the software.

The interface is easy to navigate, options are explained by text messages that appear when you hover on the options with the mouse, and the different tabs are numbered.

This means that there is no guessing in establishing the best workflow: just follow the numbers from 1 to 6 and jump at the tab number 9 for post-processing the stacked image.

You can run all the steps once at a time or set them up and run all with a batch processing: this way, you can do other stuff while the software calibrates and stacks your images.

If you are looking for a way to edit your deep-sky images and create mosaics, I vouch for Astro Pixel Processor.

PixInsight

Multipurpose Astrophotography Editor | Commercial €230+VAT | Windows, Mac OS X, Linux

Pros

• The best and most complete astrophotography editor on the market
• Multiplatform
• Suitable for Planetary and Deep-Sky astrophotography
• 45-days free trial available

Cons

• Expensive
• Extremely steep learning curve
• Requires a powerful computer to run smoothly and conveniently fast

I will be honest with you: I requested a trial (and it was granted twice), but both times I ran away from PixInsight screaming in despair.

Not that PixInsight is bad or lacks crucial functions, but because it is very complicated to use for beginners and the learning curve is very steep.

Granted, PixInsight, being the software of refinement for the category, there are tons of tutorials and guides online (Light Vortex Astronomy has some of the best ones and are free). But you need to spend a lot of time in front of your computer, particularly if you have an old one.

But if you can master it, you will be rewarded with Pro-grade deep sky astrophotography images.

A Comprehensive Video About Post-Processing

In this video, I show you how to post-process a deep sky image using some of the software discussed in this article.

While it is not a complete tutorial in post-processing deep sky images, it gives you a feeling of how easy (or not) is to use those software and where they differ. Walther ppk serial numbers interarms.

Conclusions

Stacking astrophotography images is only the first step in the lengthy astrophotography editing process. In this article, we have discussed the different software that is available to post-process the stacked image to obtain a compelling image of the night sky.

Some are free, some are commercial, some are specific to deep sky astrophotography while others are generic photography editors, and they all have their pros and cons.

This guide will help you to decide which software is best for you.

Personally, I am a fan of Astro Pixel Processor for deep sky astrophotography, as it is powerful and easy to use, and of Photoshop for its flexibility.