Tag: Siril

How To Stack Multiple Stacked Images With Siril

So how do you combine multiple imaging sessions with different calibration frames?  Well I had the same question and now I know how to do it with Siril.

Let’s say you have an imaging session on one night and then you shoot new flats the next night.  If you were to combine the raw image files and run the pre processing script now, you only have the choice to use one set of flats.

Fortunately there is a way to overcome this.  On any given night, you process the data using scripts and then you need to keep the pp_light files found in the processing folder.  All other data there can be deleted each night.

These pp_light files are already calibrated, so you can add more files on subsequent nights and then simply stack the stacked images.  Just add all the pp_lights to a sequence, register them and then do a sum stack and it’s done.

This is a great way to manage varying flat files (or darks for that matter) over multiple nights of imaging.

You can read this discussion here on Cloudy Nights

How To Add StarNet Star Removal Tool To Siril

Siril’s latest beta release software version 1.2.0 and later can now process with Starnet.  The StarNet star removal software is incredibly useful when you want to stretch a nebula’s data separate from the stars.  

 

How to Add The Script To Siril

I’m using Mac Os so these instructions pertain to this OS. If you are on Linux or a Windows PC then the software for those versions is also on this page. Download the command line tool for Starnet here.

Unzip the package and place is somewhere that makes sense.  I put mine in the Applications folder separate from Siril.  The reason I put it here is so that Siril can be updated without affecting the Starnet source files.

Open Siril and go to Preferences->Miscellaneous and then look for Software Location.

Click the open folder icon and navigate to the Starnet folder, and then select the application itself.

Once this is installed you will need to allow Mac Os to open the software.  This can be done by going to System Preferences->Security and allowing the software.

 

Once all of this is done, you can run the StarNet scripts right in the Siril application itself.

 

RGB Processing Hubble Data In Siril

There is a great deal of incredible data that the Hubble Telescope has collected.  You can download it for free on the archive site.

To practice monochrome processing, you can try it yourself.  

Go to Hubble Legacy Archive and enter the site.

Search by name or catalog number.  In this example I’ll just type in Orion Nebula.  On the advanced search section, you can narrow your search.

I downloaded 3 files, one for Red, Green, and Blue.

Save these to your hardrive.

Open Siril.  Normally you will need to convert your images to fits file format.  Hubble data is already in fits so you can now go directly onto RGB Compositing.

Navigate to Image Processing ->RGB Compositing

To the right of the colors, click on the open button and select the correct fits monochrome color data for each color.

Once they are loaded, you can preview the image on the RGB color tab.

Star Alignment

You might notice that the stars are off since we did not register the images.  You an align them in Siril by drawing a box around a section of one of the colors, then selecting “and use this alignment method”.  Select “Image pattern alignment/Deep Sky”.  Press “Align”

Now the three channels should be aligned.  You can further edit the image or download a version.

Here is my first attempt at processing the Orion Nebula.  I was pleased with the level of detail in all three channels.

This image was processed from three monochrome images using Siril and then edited in GIMP. The raw data is from the Hubble Space Telescope

RGB Narrowband Image Processing With Siril

Basic Procedure

Take images in each band such as L, Red, Green, Blue or H-Alpha, O-III, or SII.  Collect Darks, Flats, Lights, and Biases one at a time.  Note that you will only need one master set of Darks and Biases since they are taken in the dark and are not dependent on the filter used.

Each color or narrow band should be in their own folder within the master directory for the project. These bands and individual channels will be stacked to form a master for each channel.

Open up Siril and process each color or narrow band one at a time using the monochrome script.  Save the image from each band in the master folder with good naming such as red_stacked, blue_stacked etc.

Combine Monochrome Images To Form A Color Image 

Now that each color or filter band is saved, the next step is to align the images.  This procedure is called Registration.

Add all of the channels in the Conversion tab and press “Convert”.  Next align the images with the Registration tab.  Do not stack.

Now go back to Image Processing->RGB Compositing.  Here you can assign R, G, B, L, or any narrow band image to combine into a single color image.  Select them from the list.  Note that the numbering order may be different than RGB.  It might be BGR so select accordingly.

A preview will now show and you can color correct at this point.  You can open one of the color tabs and select a dark area.  Draw a box around the dark area and choose “Use Current Selection”.  Then click “Background Neutralization”.  Now check the RGB tab and see if the preview better reflects the color you would expect.

Export Or Further Process

At this point you can save a Tiff of the linear version for further processing in Gimp or Photoshop.  You could also use Siril’s image processing if you choose.