Guide: discovering Deepsky Stacker, the freeware most used by astroimagers

We want to deal with the use of this valuable tool which lets you combine multiple shots clubs made with Earth’s motion tracking but also with only a tripod for still image. For this reason, we refer to our guide on the equipment for wide field Astrophotography with DSLR cameras that we’ve posted on this blog:

Now we can continue, skipping the part of “recovery”, and coming to the software Deepskystacker; Once unloaded and installed we can run it and we are confronted with this screen, in order to achieve a correct processing I indicated the steps, numbering them in order and as in this post we are going to explain the reason behind every action, calling them 1 Point 0, 2, and so on:

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We start from the point 0; This is more a note before we get started, I wanted to point it out because the “About” menu item you can change the language of the software before you start, at our own pace, and in this I used English because this guide is accessible by anyone.

2addlight1 concerns point uploading images in long pose (defined Light frames), we will be like in this image, for this guide we choose of the shots on the constellation aquila performed with a 50 mm lens at ISO 1600, and where if we have already tried to allieare and combine the same files, we will also find the. txt files with the same name , containing information of stacking, the star rating and parameters that dss will then list on the main screen. If you want to start over completely from scratch, by realigning all the photographs and to be sure that DSS will start over completely from scratch, you can also delete all these txt albeit few bytes, and for convenience if you want to add in a few clicks all images “light frames” we can include them in the selection, DSS will not give error and load images correctly.

Let’s move on to step 2

3balancecolorsThe settings are verified as in RAW Fits ranging screen indicated by asterisks * rossi need to have balanced the colors in advance about individual raw shots are loaded.

Each checkbox enabled, followed by Apply, will generate a preview of the image with the white balance settings applied to it (you have to preemptively, choose one of the pictures “light frames” on the list, once uploaded to DSS).

Found the right white balance, that is, when we do not have a reddish or BLUE sky background, and colored stars, we can click OK and continue.

4adddarksWe arrived at point 3, which concerns the loading that will end loading files on the program, it must be said that if “flat” shots are done-or iso shots to mitigate (es. 400 iso) and AV settings, performed with an uniform light source in front of the camera/telescope or with the special flatmachine but for that I refer you to this other post:

5calcoffsetsUpload the shots dark as shown in Figure 4, we have reached the point in our guide, that is where we will select all the images in the list, shown in the picture with the letter A and the checkbox for each image sprung up; To do this we must go to the menu option shown in this last image with the number 1, and proceed by clicking as indicated by the number 2 to calculate the Offsets of the images (defined by DSS as register images, but that it is an automated task and I’d rather tackle) — calculates the values already present in the various columns, in addition to the file name and path to disk but for all the parameter that now we’re interested in Stars, or the number of stars for each image from the software, as indicated by the letter B.

After processing to calculate the offsets DSS will report these values and we won’t have to do is line up our list of images for Stars, stars. so to display immediately the best image uploaded to DSS, that we can go to set as the reference image (reference image) if lìimmagine will seem truly the best, clicking with the right mouse button on it and having the same name option, which will produce an asterisk on the photograph on the list and that will serve as a reference image as “field of view” and “star quality in the further processing of alignment and stacking (Align and Combine)

6brightAlso we tell you how we can increase the brightness of individual images because DSS presents them as very dark — by the special potentiometer to slash as shown in the figure and presents at the top right corner of the software.

7registerWe have reached the point where 5 once you click on Registering from the menu (we can also decide to click the option just below Combine, if the images have not yet been calculated Offsets as described in point 4, we will show this screen to Register Settings that I proceeded to label in order to explain it better.

We have the two pull-down screens identified with the letters a and b, and the subsequent settings shown to order 1, 2, and finally the last action to be accomplished or, once you have finished setting all the settings that now I will explain as, click 3 to begin processing and skip to step 6.

But let’s move step by step, to Actions, indicated by point a, we Register by popping up already … as indicated by the first red asterisks *, because we have already run the offsets, and vary the percentage of Select the best pictures. indicated by the second asterisk that I suggest to set between 80 and 90%, and values into practice is the percentage of clicks that are finally aligned and combined, calculating a minimum percentage of shots that will be discarded by DSS based on quality that is the number of stars along with other values in these two examples that I’ve brought you the 20% or 10%.

8percalignWe then pass on by the letter b and Advanced pulldown indicated to evaluate the tolerance percentage for the recognition of the stars in the images, shown with the first asterisk * red, usually we can use around the wide field images 10-15% with 10-20 mm, and for shots at longer focal length, you can also get off around 5%.

The option Reduce the noise … indicated on the other asterisk * red, in principle all enabled whenever you execute special other processing with other software to your image, save the final cosmetic, otherwise should enable it to reduce noise, but still must be evaluated according to the raw images and noise that arises.

9reccomandAt this point we can go to the Recommended Settings, identified by the number 1, clicking will have a summary that will be controlled, i.e. when the number of light/dark/flat frames, vary some how it processes and in our case, I indicated in figure, with the letter b.

Or B when we have the description “Your are stacking … “highlighted in red, it means that you must set one of the proposed options and once you have selected the option will change color, becoming green and I recommend generally always select the first method proposed. While the section indicated by the letter is correct, and it is already selected already green.

10reccomandLet’s see in the next image as selected the method change color lettering, while for other options selected in blue who remain can ignore them because we’re aligning images DSLR without interference filters (as the h Alpha proposed).

11stackingAt this point we can click OK and go to the last selection, the “stacking parameters we see shown in the figure, we need to look at than the default three selections indicated by asterisks * Raja but let’s see in detail starting from top to bottom:

Standard mode must be indicated so that we know that the reference image you previously selected will be the field of our final image combined, other options must be selected in case of landscape shots or if you want to combine only part of the picture but in this guide we want to give a smattering of basic functions, in order to achieve a correct image and over.

The second asterisk * red, indicating the options Enable Drizzle 2 x and 3 x must be disabled, because to perform an operation in drizzle you must first select the area of drizzle, you cannot run it all-out, otherwise an error and failure to process, but to know and learn this specific technique I refer you to this other my post and the attached video-tutorial , also on this blog:

As for the third checkbox noteworthy, indicated by an asterisk * red “Align RGB Channels..” keep it enabled because it helps that Deepskystacker sketches the alignment of RGB channels in the final image, but continuing in this post, you’ll understand why.

7registerWe can then click OK to return to the image of Register Settings, where completed all changes on settings, we can finally proceed as indicated by point 3 by clicking the last OK and starting processing software.

The latter will take time, the speed depends on the hardware characteristics of the computer with which you are doing 15 min/30 min DSS, generally with an average computer/powerful.

13finishedalignThe result of the processing will look similar to the image that I propose, dark, solid and with the histogram that we see at the bottom of the screen next to the numbers in red indicated, but which will present all three pre-aligned RGB colors as previously requested, which will help us to process the raw image.

We analyze the histogram knowing that we have to get on the same the condition where the curve we see intersects for greater length the Spike we see indicated and representing the three RGB colors, and to do that we can move all three color channels by potentiometers, 1 number indicated by the bar in red or luminance potentiometers indicated by the number 3 in red by moving to the left so that it intersects the curve peak.

14aligncolorsThe solution that we will move the rgb, from 1-down, and to explain better, I show you in this other image what it looks like before and after the modest color bars. with the previous proposed histogram to the right of the current one.

We can also notice that the picture shows very little saturated, but brighter and more detailed.
15saturationWe then pass the curtain number 2 that will allow us to give a greater saturation to the image, as you can see, and in case of perfectly balanced image allows us to better see the error on the colors and then correct it back to curtain number 1.

16luminanceadjustThe last phase, also known as that of the number 3 concerns the streaching, review of the curve, which represents the gamma of the image. As we have previously mentioned several RGB peak area intersects, more brightness and detail to scan your image, but it should also be said that the more the vertical curve is trying to intersect more area, more noise come out of the image, as well as retail. This picture has a streaching proposal that can be defined as “average”.

It is therefore necessary to mediate the use of pull-down selection in the number 3 beats “luminance” and I propose a second version milder than to compare the position of the bars, we do note that to move the stick position goes Piledriver, whilst for the second streachare Midtones bar more or less the picture, the first bar that Act is the first of the midtones , and then act on Darktones, for softening the blinds, and consequent overexposure to decrease Hightones of stars; in practice the more you choose to streachare the image by moving to the left the first bar of the Midtones, more stars will be great and will lose the colors, so you must act accordingly so as not to produce a bad result.

In both cases, showing a medium and a bland, but both with streaching the other bars correctly calibrated so as not to damage the image quality, sovraesponendola or exceeding the streaching, so then you have the choice of which final image click and proceed to a final rescue.

18saveasAnd we are at the final screen, for successfully processed, we can proceed to save processing obtained from the link on the menu called “Save picture to file …” and highlighted with the red arrow in the image. You will then be offered the save screen you see.

19saveasI highly recommend you select as shown in picture with * red “Apply adjustments to the saved image” in Options before saving, otherwise DSS will save a picture as the rough, without the changes applied so far.

We just have to give the name to the file, and save it in the TIF format (16 bit for not having problems with various graphics software) and for your information, the FITS is a less common and used by format astronomical processing software, but in this case we stop at saving this process:)

Remains the cosmetics, which may contain a slight crop to eliminate rough edges usually marked for driving or dithering, and applying the antinoise to have your astrophotography over.

I hope this guide will be useful:)

and I refer you to the next post, Hello!


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