Flintstone Stargazing

June 26, 2009

My Quick DeepSkyStacker Tutorial

Filed under: astronomy, Astrophotography — Tags: , , , — Ed @ 9:21 pm

It was suggested that I should put together a quick tutorial on how I use DeepSkyStacker to stack/process images, so this is my attempt to do that.

DeepSkyStacker is free software designed for stacking deep sky and comet astrophotography. The software author specifically disclaims its use for planetary or lunar imaging and I’ve never tried it so I don’t know how it works on those. Since my main focus is deep sky stuff (particularly Messier Objects) it’s a valuable (yet FREE! did I mention free?) part of my astrophotography toolkit.

Starting Out

The first step of astrophotography is to set up your equipment, get your telescope aligned, camera set up and so on. Let’s assume I’ve already done that. Including good drift alignment, that normally takes me between 30 minutes and an hour, the biggest part of that being the alignment. Once I’m ready to start imaging, I find the target, center it and attach the camera. For the purposes of this tutorial, let’s say I’m imaging M51, the Whirlpool Galaxy. My next step is to get the target into focus. While I have a parfocal ring on some of my eyepieces, it’s not so perfect that I don’t need to refocus when I put the camera on. Once the camera is attached, I focus it using my electronic focuser and, starting tonight, my Bahtinov Focus Mask. Once it’s as focused as I’m able to get it, I’m ready to start imaging. Sometimes, I use guiding like PHD Guiding, sometimes I don’t. It depends on how long of exposures I want to take. If I want to take longer exposures, then PHD Guiding becomes necessary (though I have a real problem with it when guiding on objects in the south part of the sky…). I generally capture my images using Autostar Envisage, which is software from Meade (the maker of my camera and scope). There are two things I really like about Envisage. First, it’s simple and quick to use and second, it automatically correlates the dark frames with the temperature off of the camera. Therefore, the images I save (using Fits3P) have already had the dark frame subtracted. While Envisage captures images, it saves a copy of each sub frame to the hard drive while stacking the best of the images and displaying the result onscreen. It has some issues, but gives me some idea if I’m getting a decent image or not, but I essentially never wind up using the stacked images from Envisage. Once I’ve captured the images I want to capture, I start up DeepSkyStacker and start processing, oftentimes while Envisage is capturing another target.

DSS Tutorial: Envisage Image

Selecting Your Images

Now that we’ve captured a bunch of images, we’re ready to stack, so I open up DeepSkyStacker.

DSS Tutorial: Open

To add my images to the list so they will be stacked, I click on “Open Picture Files” from the menu on the left. I select the images I want (you can add as many as you like from different folders if you choose) and they are added to the list at the bottom of the main pane. Once I’ve got all of the images I’m wanting to stack, I click on “Check all”. This will check all of the images so that they will be included when you stack. But wait! We’re not ready to stack yet. First, I normally click “Save the File list…” and save the list so I can reload it later. Next, I go through image by image in the list, clicking on them and unchecking the ones I’m not happy with. I generally do this visually. What I’m looking for are round stars. If I notice streaking (on all the stars) or ovals or lines or two stars everywhere there should be one, then I uncheck the image. Those images will just add noise to the final result. If I don’t have a ton of images, I may choose to keep some that are slight ovals, but generally I’m pretty ruthless. You can see in the image below that the stars are streaky. This is a reject.

DSS Tutorial: Rejected Image

Once I’ve gone through all of the images, I generally right click on the rejects and choose “Erase from disk…” I get rid of these images, because I’m never going to use them – they are just clogging up my hard drive. In the end, I’m left with a list that only contains images I want to stack. I then re-save the list of images by clicking “Save the File list…” so I can reuse it later.

Stacking Your Images

It’s now time to align and stack! I click “Register checked pictures…”. When you click on this it brings up the Register Settings dialog. On the Actions tab, I check all three boxes and set the “Select the best…” box to 100%. Then I click on the Advanced Tab. This is where the automatic alignment is set up. Generally I’ll start at 5% and click “Compute the number of selected stars” and look at the result. If the number is above 50, I raise the percentage until I get it below 50. If there are below 10, I lower the percentage and reclick the compute button until I’m happy. You can’t go lower than 2% though, so if it can’t detect stars at 2%, you’re hosed. Of course, that probably means the images aren’t very good.

DSS Tutorial: Compute Stars

Since this one came back at 14, I’m going to keep that there. Next, I click on the “Stacking parameters…” button.

DSS Tutorial: Stacking-Result Tab

I generally use Mosaic and 2X Drizzle because I can always size it down and crop it later. The effect of the settings there are explained pretty well on the DeepSkyStacker web site. On the Light tab, you can select whatever method you’d like to use. These also are explained on the DSS web site, but I generally go with Median Kappa-Sigma clipping with a Kappa of 2.00 and Number of iterations of 5. (I don’t know what those numbers mean and I haven’t played with them – they are the defaults.) On the Alignment tab, I leave it on “Automatic”. On the Cosmetic tab, I have “Detect and Clean remaining Hot Pixels” checked. They are detected at a threshhold of 72.8% which works pretty well for my DSI-II and are replaced with the median value. This detection threshhold can create long render times and weird things to happen if it’s way off. Once time mine got moved and I had bizarro results until I changed it back. It took me a while to figure it out. Okay, once everything is set, I click OK on the Stacking Parameters dialog box and then OK on the Stacking Steps dialog box. The first thing it does, is determine star positions on all of the images.

DSS Tutorial: Registering Progress

Once that’s done, it stacks the images.

DSS Tutorial: Stacking Progress

Once it’s done, I’m presented with this:

DSS Tutorial: Initial Stacked Image

Beautiful! Right? Um, did something go wrong? That doesn’t look right at all. What’s wrong? Nothing – it’s just time to adjust the curves on the image.

Curve Adjustment

Now it’s time to make the image look its best. First, adjust the RGB/K levels. I generally adjust the top and bottom levels (with Linked settings) to get a histogram similar to what’s seen here:

DSS Tutorial: Curves Step 1

When I click apply, it will re-calibrate the high and low points on the histogram and redraw the image using the new settings. This is what I get:

DSS Tutorial: After Curves 1

This isn’t quite as crazy as the one above, but it’s still not right. That’s okay, we’re not done yet. Next, on color images, I generally go to the Saturation tab and set the saturation to 18. This works best for my camera and settings, but your results may differ. Experiment with it after you do the next steps if you’re not happy with the end results.

Now it’s time for me to adjust the curves, so I click on the Luminance tab. To really understand how to get the most out of this, you’ll need to eventually understand what each of the six sliders actually adjusts, but I’m not going to get into that here. It’s better to just experiment later with them and see the results. (Just a note: I never move the 0° slider from zero – it just raises the darkest regions of the image up, and I never want or need that. ) What I do is adjust the sliders until the luminance curve (the black line) looks like this in relation to the image histogram and click Apply (you have to click Apply to see any changes you make):

DSS Tutorial: After Curves 2

Okay! Now we’re getting somewhere. The Whirlpool Galaxy is emerging from the image. It’s not perfect (it’s really red for example), but we’re getting much closer to something I can use. I next go back to the RGB/K Levels tab, uncheck “Linked settings” and move the high mark for the red up a bunch. This actually cuts the amount of red in the image. Note that I could also fix this in Photoshop later if I wanted to, but I might as well make quick changes like this here. After I hit Apply, I get:

DSS Tutorial: After Curves 3

Okay, I’m ready to save this image now. There are still some issues I’ll need to correct, some of those will be fixed when I use a Luminance layer and others will be fixed when I adjust levels and curves in Photoshop, but that’s a topic for another time. I’ve got a good image that I could either just go ahead and use or do further processing. To create the Luminance layer, I load the L images saved by Envisage and get rid of the bad frames as described above and combine the same way this tutorial describes with the exception that I don’t change saturation or color since it’s grayscale.

Final Results

After saving both the color and luminance images as 16-bit TIFs I pull them into Photoshop, convert to 8-bit (I have an older version of Photoshop), copy the lum layer over to the color image and set it as a luminance layer. After messing with levels and combining, here’s what I wind up with:

M51-The Whirlpool Galaxy for DSS Tutorial
M51-The Whirlpool Galaxy

I hope this has been helpful. If you’ve got questions, post them in the comments and I’ll try to answer them.

Update: There is now a Turkish version of this tutorial!

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  1. [...] Stargazing put together an awesome tutorial for using DeepSkyStacker check it out here http://flintstonestargazing.com/2009/06/26/my-quick-deepskystacker-tutorial/ Share and [...]

    Pingback by Great DeepSkyStacker Tutorial at The Suffolk Sky — June 29, 2009 @ 2:33 pm

  2. Awesome! Can’t wait to try this out! I’m really hoping I can figgure out what’s causing my “noise magnification” problem. Thanks for doing this for everyone!


    Comment by Jason Melquist — July 1, 2009 @ 6:53 pm

  3. Well thanks to this tutorial I have resolved my problem. Seems my settings were a bit askew for the stacking method. Now things are looking lots better! Thanks again!

    Comment by Jason Melquist — July 14, 2009 @ 10:31 pm

  4. I’m glad it helped!

    Comment by Ed — July 15, 2009 @ 4:03 pm

  5. Great tutorial, taught me a lot of things I did not yet figure out with my trial and error technique!

    Comment by james leach — August 19, 2009 @ 8:11 pm

  6. How do I use a canon eos rebel and zoombrouzer software to get the file to starstacker?


    Comment by bob — December 12, 2009 @ 7:55 pm

  7. [...] a quick thanks to Flintstone Stargazing for the Quick DeepSky Stacker Tutorial, very helpful in setting things up to stack my images. I was not able to “Mosaic” mode [...]

    Pingback by Friday was Cool and Fairly Clear, First Pics with the AT66ED at The Suffolk Sky — December 13, 2009 @ 7:07 pm

  8. Bob – I’m not familiar with zoombrouzer, but If you are taking images in RAW format, once you get those images onto your computer, I believe that DSS should be able to stack them.

    Comment by Ed — December 16, 2009 @ 9:56 am

  9. hey thanks for the tutorial, i actually am imaging m51 as i write this lol i need “HELP” once my image is stacked and saved to the output folder as .tiff/16 bit or whatever it is , i cant get any of my programs to open it!!! i have photoshop “elements” 8,, and canon’s version of photoshop,, what am i doing wrong?? i keep getting a message that says—> cant open high dynamic range files
    (HDR)/files with photoshop …im using raw files to start the resulting image after stacking is always monochrome? im going to sledgehammer the laptop very soon… my question is why would deepsky stacker,which appealed to me in the first place because it’s free .. only work for you if you also have a 700 dollar program to do your finishing work??? there has to be some way i can open theese files with elements? im absolutley not paying 700 bucks for cs4 lol adobe can kiss it… is there a plug in somewhere for hdr files?? please anybody with any answers email me @ rsteven256@aol.com thank you soooo much.. canon 20D, meade sn-8,skywatcher 8″ , 155mm apo f/3.5 <—my baby," eq5 pro synscan…

    Comment by steven — May 4, 2010 @ 9:15 pm

  10. The issue you’re running into here is that DSS saves files in a 16-bit colorspace and (I believe) that Photoshop Elements only can pull in 8-bit images. There are a number of imaging programs that support 16-bit (and above) images, but in my case, I’m a Photoshop guy (I use it for my work) and so it doesn’t affect me. An option that is available to you is to use the copy to clipboard option inside DSS and then paste the clipboard into Photoshop Elements. When it copies to the clipboard, it’s only in 8-bit mode. While not ideal, I think it would work for you. The reason that it saves in 16-bit is that there is a ton more information in a 16-bit image than an 8-bit image and so it’s trying to keep things as high quality as possible.

    Comment by Ed — May 5, 2010 @ 9:46 am

  11. Your tutorial really put me on the right path. However, it appears that it was for a color camera and not a monochrome. I have the Atik HR16 and am struggling with how to stack and register each channel. For example, I made file lists for Lights, Reds, Greens and Blues, as well as for Darks for each channel. Also made a File list of Flats for a channel. All in all, the Main group was the Lights; Group 1, the reds, Group 2, greens, Group 3, blues, Group 4, Darks thru the L filter; Group 5, Darks thru the red filter; Group 6, Darks thru the Green filter; Group 7, Darks thru the blue filter and Group 8 for the Flats, for a total of 9 groups including the Main. I have made Autosaves for the Lights, Reds, Greens and Blues, but I don’t know where to go from there. DSS won’t let me make an autosave for the darks or flats. I’m sure I probably made one or more errors somewhere along the line. Any help would be appreciated.



    Comment by Art — June 18, 2010 @ 5:22 pm

  12. Art – Unforutnately, I just don’t have any experience with processing like what you’re talking about. I’m definitely a 1-shot color guy (I’m too impatient). I’d suggest trying the Yahoo DSS group – I hear it’s pretty active.

    Comment by Ed — June 21, 2010 @ 12:07 am

  13. Very helpful tutorial.

    I was looking at some of your images and some of they are unguided with 15 or 30s exposures. Whenever I try that (just with a DSLR and a zoom lens), DSS refuses to detect stars because they already begin to trail a little. Is there some way to relax what it considers a star?

    Comment by Peter — June 21, 2010 @ 1:52 am

  14. Peter – it may not be the trailing that’s the issue – it may be that they are too faint, particularly at 15-30s of exposure. Maybe not – but if there’s not a large enough signal (the stars aren’t different enough from the background), then DSS has trouble finding the stars – you can set the sensitivity of that when stacking and preview whether or not it’s finding enough stars (see the first image above in Stacking Your Images).

    Comment by Ed — June 21, 2010 @ 11:31 am

  15. thank you so much for your help. i wondered what i was doing wrong and deleted so many sets of pictures that probably were good…oh well. I saw your orion set done with a DSLR. I am getting a used Canon1000D and digital timer. I have a Meade LX90 8in an Im new to astrophotography. what exposures, shutter timed, iso, and number of exposures do you normally use. I know this will vary. Just ballbark to get me going. I’m currently using a 10yr old point and shoot with a good manual mode to take 30 sec exposures with a mount shooting through the eyepiece. I can’t wait for the better setup. I dont have a DSI or LPI or a lap top yet. Thank you again for your help.

    George “Mo” Moore

    Comment by Mo — September 27, 2010 @ 8:31 am

  16. Great tutorial. Thanks Ed. Helped me so much.

    Comment by Guven — October 14, 2010 @ 12:26 pm

  17. re:”so if it can’t detect stars at 2%, you’re hosed. Of course, that probably means the images aren’t very good.”

    With DSS if the frames are poor and so DSS could not stack more than one image, you can boost the brightness during the registering process to overcome the darkest images.
    Set the brightness to 5.0 (FITS tab of the RAW/FITS DDP settings) and DSS might be able to detect more stars in all the images in the Regster Settings (with a star detection threshold of 2% and the Median Filter option checked).
    In Actions – Register – uncheck Stacking after Register.
    With these values all the frames are stackable
    Don’t forget to set the brightness back to 1.0 for the stacking process though.

    Comment by Tony — November 4, 2010 @ 5:41 pm

  18. Tony, I hadn’t thought of that, but that makes sense – I may add that into the next version of this tutorial.

    Comment by Ed — November 8, 2010 @ 3:06 pm

  19. Hey Ed, what happened to your other blog?

    Comment by Pierre Stromberg — November 29, 2010 @ 12:57 am

    • Um, I forgot to renew the custom CSS and domain mapping. :) It’s all good now.

      Comment by Ed — December 5, 2010 @ 3:54 pm

  20. Just getting into Astro imaging and tried DSS last night. I managed to get what for me was ahalf decent image but when I saved it then opened it in Photoshop it looked totally different and I dont know what to do in PS to get it back. if I copy the image to the clipboard and paste it into a new image in PS it looks better but should DSS not save what you see?

    Anny help would be much appreciated

    Comment by Steve — February 27, 2011 @ 5:30 am

    • There are a number of ways of saving files from DSS. I normally save with changes applied and it tends to look right when I pull it into photoshop.

      Comment by Ed — February 28, 2011 @ 3:47 pm

  21. Hi, I have been useing deepsky stacker for a long time no problems with the help of your tutorial.I changed my DSLR to a canon 600D Raws CR 2 . now after stacking I just get a narrow band in the centre & not the full image DSS 3.3.0 installed + canon 600D codec .Plaese can you help me with any tips to get a full image. Many thanks Keith.

    Comment by Keith Watson — June 5, 2011 @ 2:58 am

    • Hi Keith, did you find out what was wrong as I have the same issue?

      Comment by Malcolm — December 23, 2013 @ 2:27 pm

  22. Thank you for this great tutorial!

    Comment by Stephan Pot Photography — September 17, 2011 @ 9:00 am

  23. [...] used to but it is free (just search for Deep Sky Stacker). A helpful tutorial may be found at: My Quick DeepSkyStacker Tutorial Flintstone Stargazing . This is the program I used to stack 10 images (10 dark & 10 light) of the Milky Way seen at [...]

    Pingback by Astrophotography Thread - Page 23 — November 5, 2011 @ 10:25 am

  24. Hi, good tutorial, but I have a problem when trying to register my pictures. After checking all the pictures and making sure they are ticked, I press ‘register checked pictures’ and get an error message telling me that the pictures must be checked before they can be registered! Do you have any idea what I am doing wrong?

    Thanks, Kevin.

    Comment by Kevin — November 28, 2011 @ 2:06 am

    • I don’t – I’ve not run into that issue.

      Comment by Ed — December 1, 2011 @ 10:20 am

  25. [...] is a good tutorial on using DSS. DSS Tutorial I used this to get my head around DSS, maybe it will help you too. Jim __________________ [...]

    Pingback by DSS being a royal PITA!! - Page 3 - Astronomy Forums | Telescope Forums & Reviews | Astronomy Community — February 9, 2012 @ 9:33 am

  26. I am a newbie at this whole process so excuse the dumb questions.
    I have data from a lightbucket image. It was a simple B&W of cluster to get some data to try my hand at processing….
    I received from the imaging session and loaded into DSS: 6 exposure, a dark a flat and a bias.
    i tried your tutorial and got to the stacking part and received message:
    “the checked pictures are not compatible(width, height, # of colors, # of channels, only one master dark, offset and flat)

    DUH……what have i done wrong? or hot to proceed.

    Comment by Stephen Harris — March 3, 2012 @ 9:36 am

    • Not a dumb question at all – I run into this periodically when I (try to) use JPGs and RAW images together. In order for DSS to work with darks, flats and bias frames, they have to be the same color depth (8-bit, 16-bit, 32-bit) and the same pixel size. Often, if the images are done differently (one may be B/W, another in color) or if they are different types, DSS won’t use them. Theoretically, you could pull an image into Photoshop or another image editing progrqam and make them match. I think that would work, but can’t guarantee it.

      Comment by Ed — March 5, 2012 @ 9:48 am

  27. [...] exposure time of about 5 minutes. I pretty much use the default settings, but I found this article very helpful as a guide. It also mentions some of the points I have mentioned here (I actually [...]

    Pingback by The Milky Way - How I Shot It — July 23, 2012 @ 3:58 pm

  28. [...] [...]

    Pingback by My First Milky Way Photo - Page 3 — July 24, 2012 @ 4:20 pm

  29. [...] also found this Deepskystacker astrophotography tutorial to be very helpful. Did you like this? [...]

    Pingback by DeepSkyStacker reading wrong size RAW files from Canon 600D DSLR — September 20, 2012 @ 2:35 pm

  30. This is an excellent tutorial. Thank you so much for taking the time to put it together..

    Comment by Bevil Templeton-Smith — December 10, 2012 @ 5:05 pm

  31. [...] when I go to stack I do use only RAW. You probably have looked at DSS tutorials .. a few I liked.. My Quick DeepSkyStacker Tutorial | Flintstone Stargazing Astrophotography: Deep Sky Stacker Tutorial – YouTube .. this one is both about how to take DSO's [...]

    Pingback by Trouble With Raw Images using deepskystacker — May 6, 2013 @ 3:05 pm

  32. […] Here is a good tutorial on using DSS. Keep at it, you will only get better. My Quick DeepSkyStacker Tutorial | Flintstone Stargazing […]

    Pingback by well a new amature imaged DSO The Ring Nebula — August 6, 2013 @ 6:58 pm

  33. […] DSS likes round stars, if you have any trailing DSS will not register them. You can also lower the star detection threshold to pick up more stars. Here is a good link. My Quick DeepSkyStacker Tutorial | Flintstone Stargazing […]

    Pingback by first attempt at astro imaging — August 26, 2013 @ 8:40 pm

  34. Hi
    I like your tutorial but I am getting problems using RAW files and have given up and use JPEG so I cannot use darks. The problem when I use RAW is that I get an autosave image that is the correct height but very narrow. I have tried altering the colour balance etc but the image stays narrow. Any ideas please?

    Comment by Peter — October 16, 2013 @ 6:29 am

    • Hmmmm… I’ve not experienced what you are seeing and it seems that DSS hasn’t been updated in a long time, so I’m not sure I’ve got any good advice for you. I’m actually considering moving to Nebulosity, which is a commercially supported product…

      Comment by Ed — October 16, 2013 @ 7:47 am

    • you need to go to the yahoo group for deep sky stacker and download the beta. I had the same problem and this fixed it for me.

      Comment by Mike — November 9, 2013 @ 6:28 pm

  35. […] is definately the way.Check out those links.I think they 'll help… My Quick DeepSkyStacker Tutorial | Flintstone Stargazing http://www.stargazing.net/david/DSS/S3P2.7DSSV2HQs.pdf Deep Sky Stacker Working with levels and […]

    Pingback by I'm a bit confused. - Page 5 — December 6, 2013 @ 7:05 pm

  36. Hello Malcolm,
    I’m experiencing the same narrow band image in DSS when using my 60Da for the first time. It didn’t do it with my 20Da and I’ve tried a bunch of combinations without success. DSS did accept the images when I converted them to Jpeg, but the processing of them was impossible and besides, DSS wouldn’t accept darks in Jpeg. I can’t recall if I had the same result in Tiff, but I want to download in Raw for the best results. I think downloading the 3.3.4 upgrade just might fix the problem, but following the directions for doing that was impossible for someone untrained with computers like myself. The directions for doing this was poorly written for the non computer savy.

    Comment by John Shutz — March 10, 2014 @ 4:26 am

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