About Processing & stacking…
Before we begin the processing of images I would like to cover a few items that need to be considered.
Firstly everything listed in these tutorials is how I go about my workflow based on trial and error and adaptation from other information sources. It works well for me and the equipment I currently use. I would encourage you to try different editing suites if you dont like Raw Therapee or Siril for those of you who arent running Linux.
Depending upon your software there are a number of methods for manipulating astro photos. The primary reason I do things in differing packages is simply because there are certain steps I need to achieve and this becomes problematic if using one single package.
Take for example Deep Sky Stacker, its a good image stacker but its output is poor in the colour processing area, where as it performs well at image stacking. To date I have had less than gratifying results using this software, except when I want to stack black and white images and the result is very good.
Another stacking program is Registax6, primarily used for image stacking. The software is now quite old and hasn’t been updated since 2011 according to the download page of the website. Like DSS , Registax has been used for some time and has a dedicated following. But for the beginner these programs are not particularly user friendly and the support for them isn’t great.
You may be wondering why you would want to stack. Simply put, even shooting one RAW frame is unlikely to yield sufficient detail for short duration imaging, which for most of us is the situation we experience. At best most exposures will be 20 seconds or less depending upon the lens used. To yield more detailed images a series of images needs to be taken and stacked in order to reveal as much faint detail as possible. If one were to have a tracking mount longer exposures become possible, but without guiding the mount, even these exposures will be relatively short and necessitate stacking.
For those using windows you might want to check out Sequator
I haven’t had a chance to use it yet but will put it to the test at a later time
Prior to importing the images into your editor it is wise to create a special folder to contain only the images you are working on. This reduces the likelihood of having files going places they shouldn’t. Once this is done you are ready to go.
I prefer to pre-edit my images before stacking as this gives me the opportunity to batch process all the images to the same degree. As some of the stacking software thats currently available only has limited or rudimentary editing, I prefer to post process first and stack last. If you are using a more professional and non free editing suite, you may find the level of editing control to be greater than the free packages that this tutorial is based on. As always its entirely over to you as to how you proceed. My aim here is to provide a guideline using freely available software packages.
Also with Raw Therapee the initial interface font is too small , especially when viewed on a 27″ monitor. To change this select the button at the very bottom left of screen and adjust the font size. I use 13 point as it fits my work-space nicely.
In Rawtherapee select the folder from the file browser, it should look something like this.
On the right hand panel you can see all the main controls in a nested menu. As the image hasn’t been selected yet these controls are inactive. Once the image has been selected (double click) or select editor from the left-hand side bar, the image is loaded into the editor. The editor reads the Exif information and sets up the image in an as shot setting.
I use this method as the base point to change the image accordingly. At this point all that is done is to adjust the image as per the users camera settings automatically.
Click the first image in the set as this will become the base image. Tip – to see a larger version of these images click on the image and right click and select view in a separate tab.
You should now have the image in editing mode as shown above.The first thing we will want to do is have a little more work space and to do that we simply click the arrow bars to reduce areas not immediately needed. Note that the exposure menu is now open.
Now that we have the image in the editor and have reduced the control menus that arent currently needed, select the neutral tab on the right in the exposure menu. You will notice that the image becomes quite dark. This is the frame as it would appear before any processing. Toggle the Auto level and neutral controls a couple of times. You will notice that in the neutral position all the controls are set back to zero. Raw Therapee is now ignoring the cameras Exif data and switching off all enhancements. You can set up Lightroom, Photoshop, and a number of other packages to do this as well, either directly or by command.
In the next section we will set the parameters for the exposure and reduce noise and luminance where necessary.