This is a short version of what I did for a JWST process flow.
Using SiriL for JWST.pdf (154.8 KB)
JWST data is available from the MAST website; STScI MAST portal
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Lovely. Thx.
Hi there, quick question.
How do you make sure that the different filters are correctly aligned and the three filters I am using are not doing this?
The below is from the menu where you load the RGB filters.
To mention, I did exactly as it stated in the PDF document in regards to alignment, without success.
All three files must be the same size. You blue file is double the image size in pixels than the other two. The image scaling is not the same for all spectral filers. Image using filters less than <2.5um are typically twice the resolution of 2.5um to 5um filters images.
To use the 4.05um and 3.56um filter image with the 1.87um image you will need to upscale the 4.05um and 3.56um images to match the 1.87um scale.
Example using 3 files in the 2.5um to 5um range with the same scaling.
You will have the option of setting the alignment method if the files are the same size. You will need to select an area in the image (note: that only works if you have selected an individual channel such as green). The you can click align.
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Thanks for the reply.
Is there a way that I can rescale the bigger filter to match the others? And if so, what are the steps.
I also noticed that the size of the file depends on the exposure length from JWST, so the bigger one is usually because of longer exposure time.
I have been trying to sort this out, but it eats at my brain and it makes me a bit frustrated.
The RGB composition tool is able to resize images but assumes they will end up with the same scaling after resizing, so this works for binning differences. For more complex registrations, you should put your 3 or more files in a directory, use the convert function to rename them (with a symbolic link), run a global star registration, and maybe crop if needed the resulting sequence, then you’ll have some files to work with for colour. The symbolic links will show you which image number was which input image.
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Hello @vinvin and thank you for your reply.
I have tried the method you have detailed in your response, and I have to say that it works. The images are all resized to the correct size and all align perfectly.
Thanks once again all for your help and time, I will now to go look at space.
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To see the other images in the file, there is a new option to enable in the FITS settings about allowing different image sizes in a sequence. Otherwise, only the first image is opened, which is in general the one we want anyway.
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