Milky Way Exposure Stacking with Manual Alignment in Adobe Photoshop

Milky Way Exposure Stacking with Manual Alignment

In this video tutorial I walk through a technique for reducing noise and improving image quality by combining multiple astrophotography exposures. I also demonstrate what to do when auto-alignment tools, like Photoshop’s Auto-Align Layers function, fail to properly align your images.

Introduction

Lately, I’ve been on an exposure stacking kick. Combining a bunch of consecutive exposures of the night sky can greatly improve image quality and it has allowed me to use smaller, cheaper and more compact gear (like a point and shoot or even a smartphone) without making too many compromises in image quality. Stacking is a technique that’s been used by astronomers and astrophotographers for decades. Most of the telescope photographs that you see from observatories like the Hubble Space Telescope were made by combining hundreds of separate photographs with hours and hours of data to yield such beautiful images of the night sky.

Hubble Deep Field Image Unveils Myriad Galaxies Back to the Beginning of Time

This Hubble Deep Field Image was made from a stack of 276 frames. Credit: Robert Williams and the Hubble Deep Field Team (STScI) and NASA via HubbleSite

In the video tutorial below, I walk through the techniques that I use to combine several exposures of the Milky Way using Adobe Photoshop. The resulting photograph from combining just 8 separate exposures offers a great improvement in the quality of the image by reducing noise and revealing more detail.

If you’re drooling over the latest, expensive camera body and lens offerings in hopes to improve your landscape astrophotography, consider using image stacking instead of spending a boatload of money on new equipment. You’ll find that with some careful use of stacking, even a basic DSLR with manual controls can make some very high quality images of the night sky.

What to Expect (Before and After)

Sony RX100III, 8.8mm, f/2.8, ISO 1600, 8 x 20 seconds

In the video tutorial below, I use some relatively noisy sample images made with the Sony RX100III (read our full astrophotography review). You can see the before and after example image above. This particular tutorial focuses on the use of the Adobe Lightroom and Adobe Photoshop and addresses one of the common problems that many of our readers have experienced when following my original video tutorial on Landscape Astrophotography Image Stacking when using these pieces of software.

Stacking un-tracked exposures of the night sky requires alignment of each exposure to compensate for the rotation of the Earth. Photoshop has an auto-alignment tool that can line-up multiple exposure layers but sometimes the tool will fail to properly align the images, resulting in a low-quality final image with blurry stars. There are a lot of reasons that Photoshop might fail to align your layers: clouds, lens distortion, and even light pollution can prevent automatic alignment.

This video walks through the method that I use to align my exposures after some basic edits and I also cover what to do when the auto-align layers feature in photoshop fails to work properly. Check it out and let me know what you think in the comments.

Photoshop Exposure Stacking Video Tutorial

Alternative Layer Auto Alignment and Star Stacking Software

Adobe Photoshop is typically my primary go-to piece of software for stacking landscape astrophotos but I should also mention some of the other options that you may want to try that may produce good results. Even if it is my personal choice, Photoshop can be a beast of a program and it’s not purpose built for astrophotography. Most of the below pieces of software are made for photographs of deep sky objects but they can often also be used to make stacks of wide angle landscape astrophotos too.

I’ve had varying results on each of these pieces of software. Sometimes they work perfectly and other times they too will have problems with alignment but they’re worth a shot if you’re looking for other automatic options. If you know of any other software tools that you think other photographers will like to try, let me know and I’ll add them to this list.

Starry Landscape Stacker ($19.99)

Starry Landscape Stacker is probably the most intriguing of all the software packages that I’ve used. It’s only available for MacOSX but it automatically stacks and masks landscape astrophotography, perfect for the stuff that we love to make at Lonely Speck. I’ve had generally good success with small stacks (8-12 exposure max) but it starts to produce mixed results if too many exposures are used. I’m still putting the software through the paces but I plan to make a quick video walkthrough of Starry Landscape Stacker in the near future. If you’re on MacOSX, this is a great App to try.

DeepSkyStacker (DSS) (Free)

DSS is probably the most well-known astrophotography stacking program. A lot of Lonely Speck readers have shown me their excellent results from the use of DSS. It’s completely free and available for use on Windows.

Nebulosity ($95)

Nebulosity is an image stacking program that’s available for both Mac OSX and Windows. I’ve had the most success with Nebulosity when using longer lenses (50mm and longer) and mixed results with untracked stacks using ultra wide angle lenses. You can download and try it in demo mode to see if it works well for you.

More Before/After

In order to give you a better idea of the results that we can expect from image stacking, check out these before/after examples of image stacks made with the technique outlined in this tutorial.

Sony RX100III, 25.7mm, f/2.8, ISO 1600, 8 x 10 seconds

Sony a7II, 55mm, f/2.5, ISO 1600, 32 x 5 seconds

 

Sony RX100III, 8.8mm, f/2, ISO 1600, 54 x 20 seconds

Sony a7II, 50mm, f/2.8, ISO 6400, 16 x 6 seconds

Conclusion

Try out exposure stacking! While you’re out shooting the Milky Way, take a few extra exposures and try combining them in post processing. Even just a few exposures combined in post processing can make a huge difference in final image quality. Stacking can greatly improve the results you can get from very limited equipment. I have made it a normal practice in almost all of my astrophotos and I’ve seen a great boost in image quality as a result.

I hope this tutorial was helpful, let me know if you have any questions in the comments section below.

Equipment

I personally buy almost all of my equipment through Amazon and B&H. Each are some of the most reputable online retailers, they both have an excellent return policy and are guaranteed to have the lowest prices anywhere online. If you are considering buying a Sony RX100 series camera or any equipment for that matter, consider buying through the affiliate links on this page. You won’t pay anything extra, but Lonely Speck will receive a small commission (usually 2-4%) to help run the website. Here are links to some of the gear that I used for this particular tutorial:

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Believe it or not, Lonely Speck is a full-time job. It’s been an amazing experience for us to see a community develop around learning astrophotography and we’re so happy to be a small part of it. I have learned that amazing things happen when you ask for help so remember that we are always here for you. If you have any questions about photography or just want to share a story, contact us! If you find the articles here helpful, consider helping us out with a donation.

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The biggest contribution comes from the use of our affiliate links. When you buy through the Amazon or B&H Photo links on Lonely Speck, it costs you nothing extra, but we will receive a small commission (usually 2-4%) to help run the site.

Thanks so much for being a part of our astrophotography adventure.

-Ian

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Ian Norman

Creator at Lonely Speck
Ian Norman, co-founder and creator of The Photon Collective and Lonely Speck. Ian is a full time traveler, photographer and entrepreneur. In February 2013, he called it quits on his 9-to-5 to pursue a lifestyle of photography. Follow Ian's photography adventures on Instagram.

32 Responses

  1. Dave September 4, 2016 / 7:51 pm

    Ian,

    Thanks for the tutorial on noise reduction. One question about averaging layers in CS6 (not extended) by changing layer opacity. When all the layer opacities have been modified, is the last step merge layers one final raw file for later work in Lightroom, or is there some other function before the final merge?
    Thanks, Dave

  2. Kay August 15, 2016 / 7:19 pm

    I would love to be able to get great results photography the night sky and stars, but I only have a kit lens 18-55 mm and an 8 mm fisheye. None of them get very good results. Not to mention I live out in the country surrounded by trees. I’ve used all the recommended settings, and all I get is dark sky and stars, but no Milky Way, no meteor showers, nothing. I really wish I could afford the right lens to do this.

  3. Mike August 12, 2016 / 9:05 pm

    Ian, thank you so much for posting such clear, concise tutorials. The techniques you recommend actually make sitting at a a computer enjoyable! I am getting sweet results from a Canon 6D and a Samyang 14mm f2.8. Now if you could recommend a tutorial for staying awake easier at 3am, that would be awesome!

  4. Edward De bruyn June 23, 2016 / 7:42 am

    Hello Norman

    Rather difficult question and maybe difficult to answer. Purchased a Polarie last year and rediscovered it recently…
    So I found out when I’m really careful with the aligning of the Vixen Polarie “Polar Meter” I can get images without star trailing, up to 2 minutes with the combo A7s + 55mm. By chance I was even able to go “once” to 4 minutes without star trailing.
    Setting a homemade green laser device in to the center opening (place for the polar scope) I was able to get 4 minutes with ease (with the 55mm).
    The problem with this last combination is that you have tot take off the camera.
    Don’t have any experience with the polar scope but ordered the off axis scope from Lacerte.
    This would allow me to use the scope without having to remove the camera body from the Polarie every time I decide to move. But have to wait until I receive and test it.

    But even 2 minutes is an important improvement ( 9 sec allowed >> it would require a second exposure with the Polarie powered off.

    So I’m coming to my questions,
    1. Do you have any idea how many stacked pictures (ISO 12800 ISO) of the same sky area I would need to arrive at the same quality of “one ISO 800 image” regarding noise and detail?
    2. Is there a rule that says how many stacked images are needed for every ISO jump (200>400>800>1600..), is it two or four (presume 2) ?
    3. If the needed amount of images to stack is 2 how many images would be needed for 2 ISO jumps (800 to 3200), would it require 2+2 = 4 images versus 2exp4 = 16 images in total, (presume 16) ?
    4. And will the image quality of a stacked image be as good as a one longer exposed (lower ISO) image?
    5. Regarding Playmemories timelapse, could you convince SONY to set the total number of exposures lower than 30 frames…☺

    Did some Googling but still not a clear answer.

    Thanks if you could help me…

    Friendly greetings

  5. JC June 1, 2016 / 11:43 am

    Hello Ian, how do you stack your images without eating a lot of your RAM?
    I tried 5 images and it turns out 300MB even though I converted to smart objects and median

    Any thoughts?

    Thank you,

    -JC

  6. Grady March 23, 2016 / 5:57 pm

    What a lifesaver this was! Photoshop had trouble auto-aligning so I thought I was out of luck. The results of the manual stack of the 10 images I used compared to a single w/LR’s noise reduction was amazing! In the single exposure, the clarity of the Milky Way was non-existent & the Lagoon Nebula was completely neutered of any color. Meanwhile, the stack was devoid of luminous noise & had all the right, natural colors still present! Again, a lifesaver for my cropped sensor D5100.

    Thanks Ian for taking the time to create these tutorials as I know they’re a ton of work. Your work has been an inspiration to a lot of aspiring astrophotographers including myself! I’d love to share a 1:1 zoom side by side comparison of my results.

    Thanks again Ian!

    • Ian Norman March 24, 2016 / 2:43 am

      Thanks Grady!

      You can insert photos that are hosted by linking to them with an img tag.

  7. Michael Dempsey January 15, 2016 / 1:41 pm

    I am living in Spain and would like to buy the 100mm Sharpstar for my Lee filter holder.
    do you ship to Spain and what are the costs if you do.

  8. Fredrick November 29, 2015 / 6:29 pm

    Great tutorial as always! I love your site. Have you ever tried this with GIMP or know of anyone who has? I’ve found lots of tips and tutorials on reducing noise and stacking, but nothing on stacking for noise reduction with it. Keep up the good work!

  9. Bill Zombeck November 7, 2015 / 11:12 pm

    Ian, excellent tutorial! I’m anxious to give it a try. Question: How did you edit out the streaks caused by the jets/planes? . . . . and how does that affect the auto-alignment or manual alignment of your stack of images?

    • Ian Norman November 8, 2015 / 1:25 am

      The streaks are “automatically” removed as a by-product of the median filter. One of the benefits I forgot to mention!

  10. George November 7, 2015 / 9:52 pm

    great tutorial Ian , can’t wait to try this out to add that wow factor to some already stunning shots. Been wanting to have a greater degree of detail in some of the galaxy core photos so will try this out. Will keep you posted :)

    • Ian Norman November 8, 2015 / 1:26 am

      Thank you George! I look forward to it!

  11. Dolph November 6, 2015 / 7:56 pm

    Ian,

    I read all of your newsletters and have watched many of your tutorials with much interest. I am ready to try some stacking myself but have a question. I am going to use my Panasonic GX7 and 14mm lens. Should I enable or disable the “long exposure noise reduction” feature when shooting a series of exposures that I intend to stack?

    • Ian Norman November 7, 2015 / 12:23 am

      Try starting without it at first and see if your shots are having any banded noise or pink glow problems. If not, leave it off as it increases the amount of time it takes to record each shot. It might be helpful on particularly hot summer nights when sensors tend to produce more noise.

  12. Kevin November 6, 2015 / 5:26 am

    Great tutorial Ian! I have been trying to manually stack milky way for many times and it just fail. The use of difference blending mode just open up my eye on how easily stacking can be done.
    Also, have you try to stack by stack mode “mean”. I think this work better than “median” when there is moving cloud. How do you think?

    • Ian Norman November 6, 2015 / 11:33 am

      Mean will work nearly as well. Median tends to produce slightly smoother results because its less susceptible to showing hot pixels. Use either and pick the one that looks the best.

  13. Lynn Ross November 5, 2015 / 1:28 pm

    I watch and try many of you tutorials and find them helpful, except the one before this one where you use the median stacking method, I set the foreground smart object and then move on to the sky smart object but once I go to smart object then median filter it goes through the process but then kicks out the smart object and tells me that it needs to be rasterized … Why?

    Anyway love your site and learn a lot
    Lynn

    • Ian Norman November 7, 2015 / 12:25 am

      Lynn, are you making sure that you’re not putting smart objects into smart objects? It’s hard to fully understand what might be going on but I would check that first.

  14. Landon November 4, 2015 / 3:22 pm

    Thanks for the tutorial Ian! I’m excited to try this out.

    One question though, do you think this technique can be combined with your stitching tutorial to make medium format looking photos? Or would the stars shift too much in the time needed to take 8 photos for each area of the sky to stitch together?

    • Ian Norman November 7, 2015 / 12:29 am

      It can for sure but careful and consistent shooting would be required to keep up with time. Ample overlap would help a lot. I think practicing with a small pano, maybe not more than 4 frames, would help prove it out. I may try this myself. One last trick might be to use one wider angle shot as a sort of manual index to assist with stitching…

  15. Juan Renta November 4, 2015 / 12:15 pm

    Ian–thanks for the superb and crystal clear tutorial! By the way, have you tried this method with Rokinon 14mm f2.8 files? If so what were the results? Did you apply a lens correction to the Rokinon prior to processing the files? I ask, given the mustache distortion of the lens.

    Again, thank you and I am looking forward to your response!

    • Ian Norman November 7, 2015 / 12:31 am

      I would advise using lens correction on the 14mm prior to stacking to help with alignment. But yes, I have used this method on the 14mm Rokinon and the 15mm Voightlander with success!

  16. Hadley Johnson November 3, 2015 / 7:04 pm

    Ian–Once again, a very helpful tutorial. Two questions: (1) Is exposure stacking necessary if one is shooting with a Sony A7s and (2) Can exposure stacking be used to deal with a situation where you have a brightly lit foreground and a dark background (in other words, separately expose for the foreground and separately expose for the background)? Thanks.

    • Ian Norman November 7, 2015 / 12:40 am

      Hey there Hadley!
      Exposure stacking is never really necessary but it will always provide some improvement. Now the a7S already produces generally “excellent” low noise shots so you would probably only see an improvement from “excellent” to ” excellent-er” which might be less tangible than with a crappier setup (like a small 1″ sensor) which can being you from “okay” to “excellent.” I hope that makes sense. Regardless of gear choice now, I always shoot a stack of minimum 8 frames, even with the a7S, on compositions that I particularly like. I don’t do it for everything but on those ‘wow’ shots, I take a few more frames.

      Yes! Stacking can greatly help with bringing out foreground detail. Just keep in mind that you’ll only want to stack like exposures. You can’t combine a brighter exposure into a stack with a darker exposure as the darker exposures will compromise the brighter ones. Do one stack for the stars and one for the foreground, just like in the tut, and then composite them together after.

  17. Ben Olry November 3, 2015 / 11:14 am

    Hi Ian,

    I use a prepackaged wine bottle version of deep sky stacker on mac os. Sometimes the user interface does not update until you resize the application window, but aside from that I have had no issues.

    http://starchaser.de/deepskystacker-fuer-mac-osx/

  18. Mariano November 3, 2015 / 10:24 am

    Ian, cristal clear tutorial, I can’t wait to try these techniques. Thanks for share.

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