Astronomy Deep Sky Stacking Software

Deep Sky Stacking Programs for Digital SLR Cameras

Last Updated: 4th January 2014

A common approach to astrophotography has become the use of Digital SLR cameras (DSLR). These are relatively cheap, can be used for astronomy and ordinary terrestrial photography, and produce surprisingly good astronomy images so have become quite popular.


There’s a few basic steps required for getting started in DSLR astrophotography. I would summarise them as:
1. Buy a camera
2. Buy a tripod, telescope or other tracking platform
3. Acquire a piece of software to help take long exposure photographs
4. Acquire a piece of software to process (including stack) the photographs you take.

The question often arises from the above of what piece of software to use for stacking and processing the resulting images that you take using your camera. Or, also often the case, people don’t realise that there is software available to make this easy. So here I am going to list a few options, hopefully making it easier for anyone who finds this page.

If you know of programs which are suitable for DSLR astrophotography image processing that are not on this list please let me know, also let me know if information here needs updating. Thank you.

Software suitable for stacking and/or processing astrophotography DSLR images:

1. RegiStar

This is a fantastic piece of software for aligning and combining individual astrophotographs from digital SLR cameras. It works very efficiently with large files, is amazingly capable in aligning photographs and has quite good stacking algorithms built in as a bonus.

This software is primarily intended for simply the registering (aligning) of frames such that they can be combined. This piece of software is so good that you can combine old film images with new digital images, or digital images from different cameras with different focal lengths and all sorts. It will also easily handles field rotation (fixed tripod shots are OK) and pretty much any other distortion.

The problems I have with this software is that it does not read Canon RAW files, so conversion to some other format such as TIF is required first, that it does not handle reduction of the images which leaves you needing another piece of software (like PhotoShop) to do that manually first, and that when combining frames in to a stack it does not provide any weighting of frames or sigma exclusion of noise in frames leaving this piece of software primarily useful for registering frames and saving those registered frames, not stacking them.

RegiStar’s excellence at registering frames comes with a price, and in this case that’s about US$159.

The version of RegiStar that I am familiar with is 1.0, and it hasn’t been updated for some time (2004). This means it’s not up to date with current file types (RAW) but doesn’t detract from it’s excellent ability to align TIF images.

Find RegiStar here: http://www.aurigaimaging.com/

2. Deep Sky Stacker

This is a free and very capable piece of software for aligning, combining and performing post processing of astrophotographs from digital SLR cameras. The best thing about this software is that it’s free, and amazingly capable for something that is free.

This software will read a wide variety of file formats including Canon RAW format, and process them. I have had some issues with processing canon RAW files with respect to getting good colour balance post-stacking so often choose to first convert the RAW files to TIF before processing. This may simply be a lack of experience on my part, as I do not use this software often.

The registering capabilities of Deep Sky Stacker are very good but do not match the capabilities of RegiStar or PixInsight when it comes to getting a good alignment of frames. There are often cases I find DSS will not correctly align frames where as RegiStar and PixInsight will.

I don’t tend to like the post-processing capabilities of Deep Sky Stacker so tend to finish my use of DSS at the point it has stacked the “Autosave.tif” and take that file in to PhotoShop from there to perform post-processing.

Deep Sky Stacker’s biggest advantage is probably it’s ease of use (very intuitive and easy to use interface) and it’s flexibility with it supporting all major file formats and handling various scenarios covering most astrophotography needs.

Find Deep Sky Stacker here: http://deepskystacker.free.fr/english/index.html

3. ImagePlus

I cannot say much about ImagePlus as I have not used it for DSLR image processing. However many people do and it comes highly recommended. You can find out plenty of information about it around the web.

Find ImagePlus here: http://www.mlunsold.com/

4. Maxim

I primarily use MaximDL for image reduction, as it’s image reduction process is very painless. Provide it with a directory of all your reduction .FIT files and it will nicely sort them in to a database of reduction groups to be applied to any image you open. Open the .FIT needing to be calibrated/reduced and it will apply the appropriate reduction frames without you choosing reduction files of the correct temperature, binning, etc. This is significantly easier than any of the other packages which all require you to do more manual work with reduction frames. The benefits of MaximDL’s reduction frame handling for .FIT files may or may not be transferred to use of DSLR raw files – I have not tried reduction of DSLR images in Maxim.

MaximDL’ stacking seems fair however I haven’t had need to use it for alignment and stacking. I also haven’t tried MaximDL for large images such as DSLR, with the largest I typically use in Maxim being those from my SBIG ST8-XME.

Find MaximDSLR here: http://www.cyanogen.com/products/maxdslr_main.htm

5. CCDStack

CCDStack is one of a suit of products made by CCDWare aligned to advanced usage of telescopes.

I have used CCDStack a reasonable amount now for processing images from my ST8-XME astronomy camera and find it very usable and relatively powerful. I like features such as being able to see what data is being rejected by a sigma function on light frames and doing this very quickly and easily compared to PixInsight which shows you no preview before processing the full stack. This makes it very easy to tweak stacking parameters for a good result and apply different filtering to individual frames (such as when a satellite passes through a frame, applying harsher exclusion to that frame).

CCDStack will easily in only a handful of steps register your frames, normalise (apply weighting to) frames, apply data rejection to frames and combine frames in to a stack using weighting determined by the normalisation.

I found CCDStack to be a good and logical step up from CCDSoft. It is usable and has intuitive and useful functionality. The program seems relatively light weight also, working efficiently with a large number of files.

I have not tried CCDStack for DSLR images. It does apparently open CR2 RAW files (amongst other formats) however in my quick attempt it did not open CR2 files from my Canon 6D (I’m unsure why).

Find CCDStacker here: http://www.ccdware.com/products/ccdstack/

6. PixInsight

PixInsight is an advanced astrophotography image processing piece of software. I now have some experience using PixInsight for processing CCD images from an SBIG ST8-XME camera and RAW CR2 files from a Canon 6D DSLR and can certainly see the potential of the software.

If you want a one-stop-shop for astrophotography image processing and you are happy to spend the $250 on PixInsight, there’s a very good chance you need none of the other pieces of software listed on this page. Having said that, you will be up for a very steep learning curve. This confounded program throws brick walls up at every turn, the usability and intuitiveness is just not there (and I do battle with it on a weekly basis). I think the developers are extremely smart but need to do a few lessons in HCI (Human Computer Interaction).

PixInsight operates in a very different way to other software. They even seem to put buttons on dialogue boxes around the opposite way to what is most common just to confuse the user. The difference in how processing is done and the user interface in PixInsight makes the learning curve very steep and troubling at first. There are video tutorials online which are almost essential for getting an understanding of how to use the software before you lose your hair trying, but once concerned it is proving to be very powerful. It took me several attempts coming back to PixInsight over a few months before I became familiar enough that most of the time I don’t hit brick walls and can perform some basic functions quite smoothly (LRGBCombine, DBE, ImageIntegration, LinearFit). Yet still I find myself wanting to throw a hammer at the computer screen in frustration when I am trying to use a new PixInsight tool/process. The intuitiveness is just not there – there is nothing to guide you through using each tool, only complex options and several different ways to apply each tool which makes it confusing.

Functions such as applying a LinearFit across LRGB frames, and the Dynamic Background Extraction function on any image to flatten image backgrounds are particularly useful and relatively easy to use once you understand the basics of the PixInsight user interface.

Where other processing software has failed to produce a good result of DSLR images (software such as using DSS, RegiStar and Photoshop) PixInsight has excelled and brought out more detail in images than I realised existed in the raw data, once I have learned how.

To my knowledge there is no doubt that PixInsight is the most advanced piece of software for stacking astrophotography deep sky images. It’s set of processes and plugins is both extensive and powerful. There are also regular updates to tools. The catch is only in it’s usability and how patient you must be to work through its steep learning curve to achieve good results.

I would suggest if you are going to use PixInsight, start with DSS or CCDStack and understand the basics of astrophotography image processing before you begin the daunting process of understanding how to use PixInsight. Also, if you have easy to align good quality images then you will likely get a very good result from DSS or CCDStack in a quicker time frame than PixInsight which will require you to perform more steps.

If you want to process DSLR images with PixInsight you will need a beefy machine to run it on. It will easily consume all of my 16 gigabytes of RAM on my Core i7 64bit windows machine when processing a stack of 20 DSLR images. Programs such as RegiStar work in a significantly smaller footprint.

PixInsight is available as 45 day free trial.

Find PixInsight here: http://www.pixinsight.com/