Astronomy Image Processing Software For Mac

Windows and OS X Support Nebulosity is a cross-platform application. It runs natively in Windows (Win7-32/64, 8, 10) and in OS X 10.7-10.14 (Intel only - Version 2 supported PPC processors - Version 3.0.7 was the last to support OS X 10.5). While Nebulosity itself is fully cross-platform, many of the camera drivers required for image capture are not. Under OS X, camera control and image. Dec 05, 2016  RegiStax is a free image processing software for amateur astrophotographers, released as freeware, which runs under Windows. A compatible version for Mac OS is also available as a emu file (see Download below) Its purpose is to produce enhanced images of astronomic observations through combining consecutive photographs (an image “stack”) of the same scene that were taken over a.

  1. Free Astronomy Image Processing Software
  2. Astronomy Image Processing Software For Mac Free
  3. Astronomy Image Processing Software For Mac Pro


Astrophotography resources include software, plugins, websites and generally great information that can take your skills to the next level. The right software and tools can save you from unnecessary headaches, and help you enjoy the art of astrophotography on new levels.

It is important to maximize your time under the stars and make sure that you give yourself the best chance of successful results. I have listed many of the software applications I use on a daily basis for capturing and processing deep-sky astrophotography images. Some of these programs are free, most are not.

Oct 23, 2015  StarStaX is a fast multi-platform image stacking and blending software, which allows to merge a series of photos into a single image using different blending modes. It is developed primarily for Star Trail Photography where the relative motion of the stars in consecutive images creates structures looking like star trails. Jun 22, 2020  Photoshop is one of the most commonly used image editors for astrophotography post-processing, but there are many others to choose from. 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. Thankfully the list of astronomy software options for Mac users continues to grow. Many successful amateur astrophotographers use an all-Mac workflow from acquisition to processing. Here are some of the most promising astronomy software options available for Mac users: Planning and Telescope Control. AstroPlanner; Observatory; SkySafari 6; KStars; Starry Night 7.

Before spending your hard-earned money on software for astrophotography, it is best to research the product. If it is something that can provide value to your processing workflow by saving you time, or help you produce better results, then it is well worth the money.

For example, the “Astro Photography Tool” image acquisition software can help you maximize your imaging time on a clear night. It allows you to automate your astrophotography session by setting a sequence of exposures. It can also control your telescope filter wheel, motorized focuser, and much more.

Below, you will Astrophotography Resources for:

  • Image Capture Software
  • Image Processing Software
  • Photoshop Plugins and Filters
  • Planning Your Imaging Session
  • Polar Alignment
  • Where to Buy Equipment

If you are brand new to astronomy and are ready to take your first step towards developing your passion for the night sky, I have put together some simple guidelines to follow when deciding on which telescope to buy.

I would not recommend jumping straight into astrophotography without first learning the sky and experiencing what it is like to spend a considerable amount of time outside with your telescope. For more information, visit the “Buying Your First Telescope” page.

One of the greatest elements of astrophotography is the amazing online community of imagers willing to help beginners. This is how I learned much of what I know now, and I am happy to assist beginners learn how to photograph the night sky.

YouTube has been an amazing astrophotography resource for me as well, thanks to incredible channels such as Chuck’s Astrophotography.

The telescope I currently use for most of my Astrophotography images is the Sky-Watcher Esprit 100. I have used many different telescopes for astrophotography, but I prefer the imaging performance and consistency of an apochromatic refractor. If you would like to see a complete list of the astrophotography equipment I use for deep-sky imaging, please visit the Equipment Page.

The astrophotography setup pictured above produces sharp wide-field views of the night sky. The 550mm focal length of the telescope is a versatile distance for both large nebulae and medium-sized deep-sky targets.

Below, is an example image captured using this setup, and what you can expect to achieve using the software resources mentioned on this page (Astro Photography Tool, DeepSkyStacker, Adobe Photoshop).

The Cave Nebula in Cepheus (Captured using Astro Photography Tool).

Capturing images outside is just 1 part of the astrophotography process. The work that takes place after your images have been taken is equally important. Having the right tools and software at your disposal will allow you to develop a workflow you are comfortable with.

Choose software that will enhance your overall experience and make you want to get out an image as much as possible. There is a solution for every headache! (Except clouds)

Software for Deep-Sky Astrophotography

These are some of the astrophotography based applications I use on a daily base to capture and process my images. Having the right tools can help you produce better images, and save time during processing. Most of the software I mention below is not free.

Before I dive into the specific software applications used for controlling your camera and telescope, have a look at the ASCOM initiative and learn how the ASCOM architecture is used in many astronomy-related devices. The INDI Library is another collection of programs designed to control astronomical equipment from filter wheels to observatory domes.

With so much time and energy spent capturing those precious light frames, you owe it to yourself to have the opportunity to make your final photo a masterpiece! Personally, I would highly recommend the small investment to greatly improve your astrophotos.

Acquisition Software

There are many software applications available to control your camera and automate your imaging sessions, including:

Investing in software that allows you to enjoy capturing and processing deep sky images will allow you to focus on why you got started in astrophotography in the first place. The best astrophotography capture software is one that is reliable, easy to use, and supports a wide variety of equipment. Once you have become comfortable with the interface, your imaging sessions will involve less trial-and-error and more exposure time on your subject.

Astro Photography Tool (APT)

I began using Astro Photography Tool (APT) in April 2017. I was looking for an alternative to Sequence Generator Pro to control my CCD astrophotography sessions. I am delighted to say that APT is a fantastic and affordable choice for both CCD and Canon DSLR imagers.

This software offers much more than just camera control, such as plate solving, automatic dithering, and more. Some of my favorite features of Astro Photography Tool are the Cooling Aid, and Flats Aid.

I was able to successfully capture Light Frames, Dark Frames, Bias Frames, and Flat Frames my very first time out with APT. This software integrates with PHD2 Guiding to handle matters like dithering between each image exposure.

Connecting a dedicated astronomy camera is straight forward, and I have never had any issues when connecting hardware using ASCOM drivers with APT.

I have found APT to be a very reliable way to control my imaging sessions in the backyard. I have used a number of different cameras (with native and ASCOM drivers) with APT to capture deep-sky images. To date, I have used the APT software to control the following DSLR cameras and dedicated astronomy cameras:

  • Canon EOS Rebel T3i
  • ZWO ASI071MC Cool


I have used SharpCap to frame my imaging target, and to focus my telescope. SharpCap is responsive and lightweight. I can quickly connect my camera for a near live-view look at my desired area of the night sky.

This software is extremely useful when focusing as well. With a Bahtinov mask attached to the telescope, I can fine-tune the focus of my imaging area using SharpCap.

I also enjoy the Polar Alignment feature in SharpCap. Using my autoguiding camera, SharpCap will plate solve the images allowing me to align the RA Axis of my mount with the North Celestial Pole.


For several years of my deep-sky astrophotography journey, I used BackyardEOS for camera control. It has several handy features that make imaging with your Canon DSLR and telescope a more enjoyable experience.

Early on, I used the Canon capture software that came with my DSLR, EOS Utilities. This worked well for me and I was quite happy with it. A few friends of mine talked about how great BackyardEOS was, so I finally decided to upgrade.

Backyard EOS was designed for astrophotographers, and as such has numerous tools to assist you in the field. The star focus module (FWHM) and dithering compatibility with PHD2 guiding would have to be my favorite features.

I also love the interface, and the robust file-naming and description options. The company offers a 30-day trial, so give it a go for yourself.

Own a Nikon DSLR? Try BackyardNIKON.

PHD2 Guiding

Love it or hate it, PHD2 Guiding gets the job done. Unless you are blessed with a high-end astrophotography mount that doesn’t require guiding such as the Paramount MYT, you will likely need an autoguiding system to keep your stars round during a long exposure.

This application communicates with your telescope mount to “lock-on” to a guide star so that your image frames are nice and sharp. Good polar alignment will help, but autoguiding with PHD will make sure that your images are sharp during exposures of 3-minutes or more.

Related Post:5 Tips for Better PHD Guiding

Sequence Generator Pro

This software is still new to me, but I can see the potential for complete automation of my deep-sky imaging in the backyard. Once I am able to construct an observatory, I will likely control my sessions largely with Sequence Generator Pro (SGP).

I used this software in it’s most basic form during my experiences with the ZWO ASI071MC-Cool camera in March 2017. This software offers a generous 45-day, full-featured trial version.

If you’re interested in the computer I use for controlling my camera and telescope, I’ve written a detailed post about the PC I now use. There are several options available for controlling and automating your astrophotography equipment, but I prefer the convenience and practicality of a laptop computer.


The ZWO ASIair mobile app is installed on my android smartphone and tablet. This is a camera control unit for ASI cameras such as the ASI294MC Pro one-shot-color camera and ASI290MM Mini guide camera. I enjoy the freedom and simplicity of this system as the internal Raspberry pi based computer rides along with my telescope without the need for an external imaging laptop.

The ZWO ASIair mini-computer riding along on top of my primary imaging telescope.

Image Processing Software


DeepSkyStacker is an amazing free program designed for astrophotography. It simplifies the pre-processing steps required to create an astrophoto by automatically registering and stacking your images into one hi-resolution file.

This is where you will submit your light frames, dark frames, bias frames, and flat frames that you captured during your imaging session. You can then bring the file it creates into Adobe Photoshop for post-processing.

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I use DeepSkyStacker in its most basic form. I prefer to organize all of my best light frames in Adobe Bridge (Any RAW format photo viewer will do), and then bring those images into DSS for registering and stacking.

This basically means that it will automatically stack all of my images on top of each other, and create a high-resolution .TIF file that I can then process in Adobe Photoshop.

For a detailed tutorial on how to use DeepSkyStacker, you can download my premium image processing guide. Alternatively, you can visit the tutorials section to see DSS in action in a variety of scenarios.

Adobe Photoshop 2020

Adobe Photoshop is a very powerful and flexible program for processing all types of photographic images. The power in Photoshop lies in its ability to stretch your pixel data further. By using adjustment methods such as levels and curves, you can bring out more color and light from your deep-sky object.

There are plenty of other options when it comes to post-processing an astrophotography image (PixInsight for example) – but Photoshop will always be my personal favorite.

I have recorded several Photoshop tutorials on my YouTube channel over the past 5 years.

One of my Photoshop Image Processing Tutorials on YouTube.

Photoshop Image Processing Tutorial (Video)

Here is an image processing guide for Photoshop that will show you how to turn an unprocessed image into a final astrophoto. The Photoshop actions and plugins used in this tutorial video can be found on this page.

I have put together a premium image processing guide, sharing all of the specific techniques I use in DeepSkyStacker and Adobe Photoshop. This guide is over 100 pages long, and you can download it here.

Installing Astrophotography Plug-Ins in Photoshop

There are a variety of custom astrophotography plugins available for Adobe Photoshop. They accomplish actions in Photoshop such as noise-reduction, gradient removal, and everything in between.

To install plugins to your copy of Photoshop, you will need to drop the downloaded file into the Plug-Ins folder. The file path should be something like: Program Files > Adobe > Adobe Photoshop > Plug-Ins. This is where the 8BF files such as Gradient Xterminator will need to be placed. Once installed, the new tools will appear under the filter drop-down menu.

Adobe Bridge

This application is an extremely handy resource when organizing and previewing your astrophotography images. I use it as a key part of my current workflow. I have been using Adobe Bridge for astrophotography for several years now.

The power of Adobe Bridge is its ability to preview hundreds of raw images files at once. The metadata for each frame is displayed, giving you access to all of the important details including ISO, Exposure length, Color mode, and much more.

Adobe Bridge makes it easy to view your entire imaging session at a glance. You can quickly remove frames that include satellite trails or frames with poor tracking.

Astronomy Tools Action Set (Photoshop)

This might be the single most important purchase you will make in your adventures in astrophotography. Noel Carboni’s astronomy tools action set is a must-have for anyone processing their astronomy photos in Adobe Photoshop.

Some of the actions I regularly run when processing my images are; Enhance DSO and reduce stars, Make stars smaller, and Increase star color. My current processing workflow includes these actions. You can view my video tutorial processing the Rosette Nebula using this action set here.

It might seem strange paying for “actions” that you could probably do yourself in Photoshop. However, this plugin will save you hours and hours of experimentation with proven processing methods for astrophotography.

Gradient Xterminator

This is another “must-have” for astrophotographers that use Adobe Photoshop. The Gradient Xterminator plugin is especially handy if you capture your images under light-polluted skies. With the click of a button, you can remove horrible gradients and vignetting in your night sky images. Running the Gradient Xterminator filter is one of the first steps I take when processing any of my astrophotos.

Using the Gradient Xterminator plugin in Adobe Photoshop

HVLG (Hasta La Vista Green)

HLVG is a plug-u filter for Adobe Photoshop that does a great job of removing the green noise from your images. This plugin was designed by the legendary astrophotographer Rogelio Bernal Andreo. The idea is simple. Since there are no green objects in space (with a few exceptions of course), the green data in your deep-sky image is usually noise. I only use this filter in situations where the green noise is obvious.


StarNet++ is a simple program that allows you to remove the stars from your astrophotography images. It is free to download, and you can run it as a stand-alone tool. StarNet++ is an invaluable tool to have when processing your images. It allows you to quickly separate the stars from your image for more control over your image processing.

Topaz Labs DeNoise AI

Noise Reduction is a critical step of the image processing workflow. Topaz Labs DeNoise AI offers you an effective way to carefully remove noise from your images without destroying important details.

I have found this Photoshop plugin to work even better than the noise reduction tools found within Adobe Camera Raw. This filter can help restore your deep-sky or nightscape images with uneven, color noise in the darker regions. Highly recommended!

Topaz Labs DeNoise AI Noise Reduction Software.

Planning Your Imaging Session


Astronomy Tools Field of View Calculator

Free Astronomy Image Processing Software

When deciding on your next project (or telescope purchase), it is essential that you understand the image scale of your imaging system. You’ll want to match the right camera to the right telescope to maximize the data you collect.

The Astronomy Tools Field of View (FOV) calculator lets you easily see what the image scale of your system will be. It provides a preview of your intended deep-sky or planetary target to show you exactly how big it will be with your camera sensor.

This tool will present you with the focal ratio, resolution, field of view, and Dawes limit of your imaging system.

The Astronomy Tools FOV Calculator

Stellarium (Planetarium)

This is free software you will need to install onto your computer. This is probably the most well-known free planetarium software and is straight-forward and simple to use. I also recommend the mobile app version of this software. Stellarium is fantastic because you can customize it to your observing conditions.

This includes being able to upload a custom landscape of your location! I plan on uploading a panoramic shot of my backyard in the near future to get an accurate rendition of my observation window.

You can also set options to view deep-sky objects in the same field of view as your telescope, and your camera sensor! No longer will you be surprised to find out that the object you planned on imaging is bigger than your field of view.

This goes a long way in regard to the preparation of your imaging session.


AstroBin is a fantastic resource for planning your next imaging target. By researching the results captured by other amateur astrophotographers, you can get a sneak peek into the performance of specific gear. If you are looking for example images using a specific telescope or camera, you can use the search function to filter the images based on that particular piece of gear.

Another way to use AstroBin is to get a better idea of how your next project may turn out. For example, you can browse images taken by others to see how large a particular galaxy will be in your telescopes field of view. The advanced equipment details and technical cards included in the Astrobin gallery will provide you with the answers you need.

A service like AstroBin is geared towards astrophotographers, so it’s likely your best choice for hosting an image gallery. The forum, big wall, and image of the day features add an element of competition and comradery to the group. This website can be an incredible source of inspiration.

“The Big Wall” on AstroBin

The idea of posting one of my images to a gallery where it will be seen by some of the best amateur astrophotographers in the world forces me to step up my game. An image that’s getting posted to Astrobin goes through a long and thorough processing treatment because I know it will be enjoyed in high resolution from corner to corner.

I gladly pay the yearly membership fee to not only build out a large archive of organized high-resolution images but support a unique and growing community of amateur astrophotographers.

Mac Astronomy and Astrophotography software

I currently collect and edit all of my astrophotography images on a PC computer, but what about Mac users?

The post-processing side of things is easy, Mac users can use Photoshop, Lightroom, PixInsight, or any other of the premium creative tools. However, there are fewer options available for the pre-processing and capturing processes.

For example, many users find themselves looking for a stacking software for the Apple Mac, because DeepSkyStacker was designed for PC’s (I suggest using Astro Pixel Processor).

Thankfully the list of astronomy software options for Mac users continues to grow. Many successful amateur astrophotographers use an all-Mac workflow from acquisition to processing.

Here are some of the most promising astronomy software options available for Mac users:

Planning and Telescope Control

Image Acquisition Software

Pre-Processing and Stacking Software

Modifying your DSLR Camera

If you’re thinking of modifying your existing DSLR camera for astrophotography, you have two options: perform the mod yourself using a tutorial, or sending the camera away to get a professional modification service performed. Unless you are very technical, and are used to taking apart small electronic devices, I would recommend option 2.

Gary Honis has put together a number of videos and tutorials explaining how to modify your DSLR camera for astrophotography. The act of modifying a DSLR camera involves removing the IR cut filter that blocks certain wavelengths of light produced by deep-sky nebulae. (Particularly the pink-red emission nebulae).

Astronomy Image Processing Software For Mac Free

I was able to successfully modify my Canon Xsi (450D using Gary Honis’ detailed and information YouTube video.

Gary Honis is not the only expert in this field. Hap Griffin also offers this service, as well as many others.

Weather Forecasting and Sky Data

Amateur astrophotographers check the weather constantly! Clear skies are what we need to accomplish our goals, and depending on where you live, they can be hard to come by.

View my list of recommended astronomy apps for your mobile phone or tablet. These include sky maps, astronomical weather forecasting, and observation aids.

I like to use a combination of tools to get a good prediction of the weather before setting up my gear.

Weather Website Resources

I enjoy using the Clear Outside astronomy app on my Android phone. This app seems to be more accurate than the Clear Sky Chart, based on my own personal experiences. I also prefer the format of low-medium-high cloud cover as opposed to seeing and transparency.

Astronomy Image Processing Software For Mac Pro

When planning my astrophotography sessions, I use a mix of many weather resources to gauge the conditions I can expect. The app is completely free, offered by First Light Optics.

I hope that you have found these astrophotography resources helpful in your quest to improve your images. It took me years to build this library of software that I use for each and every photo I capture.

If you would like to see some of this software in action, have a look at my image-processing tutorials.

Deep Sky Stacker Tutorial

I have been using DeepSkyStacker to get the most out of my astrophotography images since I began shooting through a telescope in 2011. This useful and easy-to-use freeware tool simplifies the pre-processing steps of creating a beautiful deep sky image.

The concept of stacking in astrophotography is simple, by combining multiple images together, the signal-to-noise ratio can improve.

With so much time and effort going into the acquisition stages of astrophotography, it would be a shame not to achieve the best possible results when stacking your images. In this post, I will explain the DeepSkyStacker settings I use to stack and register all of my astrophotography images.

If you haven’t already done so, download DeepSkyStacker for free. The version I currently use to stack and register my astrophotography images is DeepSkyStacker 4.2.3.

I have used DeepSkyStacker to align, calibrate and integrate every deep-sky astrophotography image I have ever taken. It is well worth your time to learn how to use this free software successfully, as you will enjoy it for years to come.

Over the past 8 years, I’ve stacked images created using a DSLR camera, dedicated astronomy camera, and CCD Camera. Whether you are stacking .RAW image files from my Canon DSLR, or .FIT files from a CCD camera (or dedicated CMOS), the right settings can be the difference between a good image, and a great one.

Integration is the key to great astrophotography image. This is the reason why amateur astrophotographers spend multiple nights collecting pictures on a single deep sky target. Calibration is another vitally important component of the process, as this removes unwanted elements from your image that would otherwise spoil the picture.

For an in-depth, step-by-step guide to DeepSkyStacker and Adobe Photoshop, please consider downloading my premium image processing guide.

Page 35 of my premium image processing guide.

Main Features

For many amateur astrophotographers, DeepSkyStacker (DSS) is an integral part of their image processing workflow. For myself, I find that DeepSkyStacker does an exceptional job of registering astrophotography images taken using a variety of methods. This includes everything from untracked DSLR and camera lens shots to deep sky astrophotography through a telescope.

DSS can register images of everything from a wide-angle Milky Way panorama to a deep sky emission nebula. Most of my experience with this software has been on a Windows 10 PC, stacking Canon RAW files from a DSLR. To run Deep Sky Stacker on a Mac computer, a workaround such as using a virtual machine is necessary.

Let’s take a look at the main features of this software:

  • Registration of picture sets
  • Creation and use of offsets, flats and dark frames
  • Native use of RAW files from most DSLR
  • Multiple Stacking methods including average, median, kappa-sigma clipping and more
  • Preview of all pictures including RAW and FIT file types
  • Simple and intuitive user interface

DSS offers some advanced features I have not yet put into practice myself, such as comet stacking. The steps outlined on this page are most useful for beginners using a DSLR camera to capture their images. The official website offers some great resources for understanding how the process works.

If you want to review the statistics of your images and stack them as they are captured, you can try using DeepSkyStacker Live.

It’s important to remember that DeepSkyStacker was meant to integrate and calibrate your data into a useful intermediate file. It does not include the robust image processing tools of an application like Adobe Photoshop.

All of the images that run through the pre-processing stages in DSS are then brought into Adobe Photoshop for final image processing. The image below shows a stacked image before and after processing in Photoshop.

See the difference post-processing makes?

When you have successfully created your intermediate file in DeepSkyStacker, you can process it much further. Read my Photoshop image processing tutorial for a basic walkthrough of the process. Or, download my premium processing guide for an in-depth look at all of the techniques I use to process astrophotography images.

Tutorial (Deep Sky Images)

There are several applications available to register, calibrate, and stack astrophotography images including Astro Pixel Processor, and PixInsight. However, DeepSkyStacker is completely free and continues to receive new updates from the developer (version 4.2.2 was published in August 2019).

The software may seem confusing at first, but the good news, generally the default settings work best.

I regularly capture images on the same deep-sky object over multiple nights to increase the signal-to-noise ratio. I shoot through heavy light pollution in my backyard, which means I need to capture up to 4x or more the amount of exposure time someone living under dark skies would (see this article for a better understanding of this calculation).

I have experimented with many different combinations of options for stacking DSLR raw files, and have found that most of the default settings work best. DSS includes a handy “recommended settings” tab, that will highlight helpful settings to use based on your image data.

File Preparation Before Stacking

If you follow my astrophotography tutorials, you will have captured light frames, dark frames, flat frames and offset/bias frames during each of your imaging sessions. These support files (calibration frames) will go a long way towards improving your final image. I recommend capturing new calibration files for each night of imaging unless you are certain that your master files match your light frames.

Only stack your best images

Before opening the files in Deep Sky Stacker, I pre-qualify the images I want to stack. I use a RAW image preview application called Adobe Bridge to review and organize my images. Any photos with football-shaped stars from hiccups in autoguiding are tossed in the recycling bin. The same goes for frames with airplanes, satellites or passing clouds.

You can also use the scoring feature built into DeepSkyStacker for a calculated interpretation of your image data.

Using the Score Feature

After registering your pictures in DeepSkyStacker, it will provide a score for each of your light frames. The values of the score will vary widely depending on the imaging equipment used. There is no benchmark number to achieve.

This is handy when stacking your final picture, as you may want to only include the light frames with the highest score in your final stack. Instead of clicking Check all as you did when registering the files, click Check above a threshold.

If you have prescreened your images already, you will likely stack most of the images you registered anyway!

Remember, the scores will only appear after you register the picture files. Once you have selected a minimum score value, DeepSkyStacker will only stack your best light frames into the final image. I recommend choosing a minimum score value that will use at least 70-80% of your light frames, as you want to use as much integration time as possible for the best signal-to-noise ratio.

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Stacking FIT files (CCD or Dedicated CMOS)

If you are transitioning from a DSLR camera to a dedicated astronomy camera, one of the first hurdles to overcome is the new file type the camera produces. It’s called “FITS”. Stacking FIT files in DeepSkyStacker presented a bigger learning curve than I anticipated.

I’ve had most of my success using trial and error. For example, I was able to produce an image with the correct color balance using a dedicated astronomy camera with an RGGB Bayer pattern. I discovered this during my Markarian’s Chain imaging session, by using a specific color adjustment setting.

You can adjust the RAW/FITS Digital Development Process Settings to make sure that you have the correct Bayer Pattern Filter for your specific camera selected. For most color dedicated astronomy cameras (including the ZWO ASI294MC Pro camera I use), the correct setting is Generic RGGB.

These files can be hard to preview, due to the fact that they need to be debayered first. For this file type, I inspect and remove poor quality frames within DeepSkyStacker itself. This method can be a bit tedious, but a necessary step to ensure your final image only includes the best data.

Keep Your Image Sets Organized

Organize your images into 4 folders. Lights, Darks, Flats and Offset/Bias.

In the Main Group:

Open Picture Files

Select all of your light frames from your first night of imaging. Since you have already reviewed and approved all of the images in this folder, this is simply a matter of selecting every RAW file in your light frame folder.

Dark Files

Select the dark frames you captured from the same imaging session. The images need to be the same exposure length, ISO and temperature as your light frames. These can be easily captured with the lens cap on your camera. I recommend using a minimum of 15 dark files or more.

I believe that dark calibration frames are a must for DSLR astrophotography. In my experience, they reduce a significant amount of noise in the final image through dark frame subtraction.

Flat frames

Flat frames require a little more effort than dark frames but can be collected in a very short amount of time. Stretch a white t-shirt over the objective of your telescope, and smooth out all of the folds.

Point your telescope towards the blue dawn sky (or an evenly-lit artificial light source), and capture a number of shots with your DSLR set to AV mode. 15 flat files can make a significant improvement to your final image. They remove artifacts such as dust and correct vignetting and gradients in your image.


Offset/bias files are quick and simple to capture with your DSLR camera. Just take about 15 exposures with the lens cap on your DLSR. These exposures need to be the fastest possible shutter speed using the same ISO as your light frames. (On the Canon 450D, that’s a 1/4000 second exposure)

How to Combine Images from Multiple Nights

Use the tabs to group your image sets

Once you’ve got your picture files (lights) and all of your support files loaded into the main group, it’s time to load up your files from night 2. Click on the small Group 1 tab at the bottom left of the screen, and repeat the process for opening files from imaging night 2.

Remember, you can stack different variations of exposures together in Deep Sky Stacker. This means a range of ISO sensitivity and exposure length.

Some imaging sessions may include all 3 supports files to complement the light frames, some may not. This is fine. After all of the image files have been loaded into their respective categories, it is time to register and stack the frames into a single file. Finally, make sure to click “‘check all“, to make sure that all of the frames you have loaded are selected.

Before we click Register and Stack images, let’s take a look at the current default settings.

Accessing the Register and Stacking settings is accessible by clicking “Settings…” under the options tab.

The default settings for registering is set to a 10% star detection threshold. In my experience, the default value of 10% has worked very well for stacking images captured using my 12MP Canon EOS Rebel DSLR. If you decrease the star detection threshold, DSS will detect fainter stars. The number of stars in a given light frame is displayed in the lower half of the screen.

With a light frame selected, look for the #Starscategory.

The following checkboxes should be checked before moving hitting “OK”, and letting DSS begin its process.

  • Register already registered pictures
  • Automatic detection of hot pixels
  • Stack after registering

The DeepSkyStacker website states that the automatic detection of hot pixels only works if using Super-pixel, Bayer Drizzle, bilinear and AHD interpolation modes. However, I leave this box checked regardless and hot-pixels and stacking errors have never been an issue.

Stacking Parameters

Unless you are experiencing errors in the stacking process, leave all of the values in the stacking parameter dialogue box unchanged. Yes, this sounds like a conveniently simple option, but default values are usually set for a reason.

If you want, go ahead and click on the different modes in the “Result” tab. The program will show you a preview of the final composure created using Mosiac and Intersection modes. I prefer to use Adobe Photoshop for the final framing and cropping of the image.

As for the stacking parameters of the light and dark frames, Kappa-Sigma clipping and Median work well in the Light, Dark, Flat and Bias/Offset categories. I do not use any additional features such as the detection and cleaning of hot pixels in the Cosmetic tab.

One setting I do change, however, is the output location folder of the Autosave.tif file. I prefer that these images populate in a specific folder of my choice rather than mixed in with a folder of light frames.

Depending on the quality of and amount of light frames available, I usually select the best 80-90% of pictures and stack them.

Ready to Stack?

You’ve got all of your lights, darks, flats and offset/bias frames loaded. The default settings are currently selected, and the ever-comforting green bar is displayed (confirming your use of all support files) But wait, if only there was a way to confirm all of the files are as they should be.

The Stacking Steps Window

Before you run DSS, be sure to check and see if there are any warnings in the dialogue window. In the case above, there was a single Flat frame with a miss-matched ISO speed. These warnings are useful for catching little mistakes in your file organization that can potentially make a big impact on your image.

At this point, you can remove or add any frames based on the information that DSS has provided.

If all looks well, and there are no more warning messages in the Stacking Steps window, you can proceed to run the register and stacking process. I enjoy the information preview about the estimated total exposure time.

Deep Sky Stacker Tutorial (Video)

In the video tutorial below, I walk through some of the basic settings used in DeepSkyStacker. I then bring the image into Adobe Photoshop for further image processing.

When DSS has completed its process of registering and stacking all of the image frames together, a preview of the constructed Autosave.tif file is displayed onscreen. Based on the design of this software, you would think that the next logical step would be to make adjustments in the RGB/K Levels, Luminance, and Saturation area.

If you plan on processing your image in Adobe Photoshop, I recommend leaving these settings as they are.

Balancing levels, curve adjustments, and boosting saturation are all staples of an Astrophotography processing workflow in Adobe Photoshop. Photoshop offers many more options and a higher level of control than Deep Sky Stacker for such edits.

What about the Recommended Settings option?

DeepSkyStacker has a “Recommended Settings” option that offers suggestions based on the image files submitted. Some of the recommendations include changing the stacking mode used such as “Use Median Combination Method”.

I have tested both the recommended settings and the default settings and found the default to produce better results.

If you are determined to see the subtle differences in the final stacked image, you can go through the entire process using the default Deep Sky Stacker settings vs. the recommended settings. I found that the recommended settings had varying results, with fuzzier more washed-out stars than the original stack.

I prefer to try both stacking methods and compare the results on a per-image basis. You may find that the stacking modes suggested by DSS improve your image.

Below: The Andromeda Galaxy stacked in DeepSkyStacker. Final processing in Adobe Photoshop.

To view the techniques I use in Adobe Photoshop to finish the image, watch my image processing tutorial video featuring the Soul Nebula. There is a link in the description to download the RAW data and process the image yourself.

Stacking wide-angle Camera Lens Images

Although I mostly use DSS for deep sky images, it is also very useful to stack wide-angle astrophotos through a camera lens as well. The same signal-to-noise benefits can be achieved by stacking multiple images together.

You may experience a number of issues when attempting to register and stack images that include terrestrial elements such as trees or any other terrestrial landscape. If you are using a star trackerto compensate for the apparent rotation of the night sky, the ground will blur. If you are using a stationary tripod (non-tracking), it’s the sky that is moving between each frame.

The photo below was captured using an iOptron SkyGuider Pro to track the night sky, with a DSLR camera and wide-angle lens mounted on top. As you can see, the rooftop of my neighbor’s house is blurred, because DSS registered the images with the moving sky.

An excessive amount of movement between the night sky and the foreground (over time) can make stacking images like this difficult. One solution is to photograph the night sky and foreground separately and combine the images together in Photoshop later.

Recommended Settings and Tips

For my wide-angle shots, I use a modified Canon DSLR with a light pollution filter. The settings I recommend below will work well for a modified DSLR shooting through moderate to heavy pollution. Those shooting with a stock DSLR may have to experiment with these settings to produce a pleasing result.

White Balance Settings

If you are using a modded DSLR, make sure to leave the white balance checkboxes unchecked. Using an auto white balance or the “camera white balance” with a modified camera will produce odd results. I would also suggest checking off the “set the black point to 0″ option.

This should provide you with a final image with a background sky that is much easier to correct in post-processing. Gradient Xterminator does a great job of correcting gradients in wide-angle shots of the night sky.

Recommended Settings

As for DeepSkyStacker’s recommended settings, the graphic below shows you which ones I like to use on a wide-angle starry sky photo. One of the important settings is to use Per Channel background calibration – as the RGB background calibration does a poor job of producing correct colors in my experience.

Scenarios and recommended settings:

  • Scenario: You are processing long exposure and possibly good SNR images
  • Recommendation: Use AHD debayering
  • Scenario: If you are using a modded DSLR
  • Recommendation:Reset all white-balance settings
  • Scenario: If you are processing narrowband images (especially Ha)
  • Recommendation: Use super-pixel mode
  • Scenario: You are stacking (x amount) of light frames
  • Recommendation: Use Sigma-Clipping combination method
  • Scenario: You are creating a master dark from 31 dark frame(s)
  • Recommendation: Use Sigma-Clipping combination method
  • Scenario: If the resulting images look too gray
  • Recommendation: Use Per Channel Median combination method
  • Scenario: If the color balance in the resulting images is hard to fix in post-processing
  • Recommendation: Use RGB background calibration

What to do if DeepSkyStacker Crashes

I have experienced this issue many times while attempting to register and stack both RAW image files from a DSLR and .FIT from a CCD camera. It can be a frustrating experience, especially if you have left your computer to let DSS do its thing. You come back 20 minutes later to view your stacked image, and instead, find an error message saying “This program has stopped working” or any number of other error messages.

I have found that the following steps can decrease your chances of producing an error using DSS:

1. Don’t run other applications while stacking

I am a multitasker. Usually, I have 5-6 windows open at a time from my Google Chrome browser to Adobe Photoshop. This all uses RAM on your machine, which DSS uses to process your image. Give DeepSkyStacker your full RAW capacity to use during its process.

2. Pay attention to the options you’ve selected

Certain options, such as “superpixel mode” are very demanding on your system and have been known to crash. Take a screenshot of your settings used before stacking, so you can compare results and try another stacking parameter next time.

3. Try stacking fewer images

The more frames you stack, the more time and resources DSS will pull from your machine. Try being more selective with the images you plan to register, and only include the absolute best images.

4. Try an external hard drive

You can tell DSS to utilize the space available on an external hard drive to render your images. The temporary files can require up to 100GB of space or more depending on the number of images in the set. This destination is selected under Settings > Stacking Settings > Temporary Files Folder.

I hope you were able to learn something new about DeepSkyStacker following my tutorial. It’s one of the few applications that hasn’t changed very much since I began using it in 2011, and it continues to deliver consistent results.

Alternatives to DeepSkyStacker

Everyone prefers to process and stack their astrophotography images in their own way. DeepSkyStacker isn’t the only software available to calibrate and stack your image frames. Here is a list of alternatives to DeepSkyStacker:

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