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Tutorial:
AstroImageJ, make masterflats from CR2 files


AstroImageJ, astrophoto editing tool

  1. Introduction
  2. Download and Installation
  3. My own downloadable macros
  4. How to use "Masterflats from CR2 files" macro*
  5. How to use "Calibrated object files from CR2 files" macro
  6. How to align rggb files
  7. How to stack rggb object files

How to use "Masterflats from CR2 files" macro:

If you don't already have calibrated masterflats from this macro you start with this:

Prepare to have a directory with your Canon raw CR2 sub flats files. Files with other extension than CR2 will be excluded. You should have moved away or erased sub flats that are not good. It should look something like this:

AstroImageJ, AIJ: testflats

Here is four sub-flats, why do they have a pink color? That's because white color cause the green channel to dominate, the sensor normally has it's highest sensitivity i green wavelength. It could look different for your system. Red, green and blue color should be of equal strength and about 50% of maximum.

Read more deeper about color flats under my tutorial:

  • Flatcalibration
    Flatcalibration tutorial by Astrofriend

  • AstroImageJ, AIJ: run macro Make masterflats

    Run the macro "Masterflats from CR2 files"


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    AstroImageJ, AIJ: open subflat directory

    First it will ask you in which directory where you have your sub-flats. You will not see your files, only the directory.


    AstroImageJ, AIJ: make masterflat log

    You will see a log of what's going on.
    First it read the sub flats to an internal virtual stack.
    Demosaic (divide them in separate colors).
    Bias calibrate.
    Normalize.
    Through away abnormal values.
    Save as 32 bit floating point files in subdirectory masterFlat.


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    AstroImageJ, AIJ: masterflat directory with masterflats

    Here are the four masterflats, they are corrected for abnormal values, very important to make good quality masterflats. Everything done almost automatic. The cfa directory is just temporary, normally not needed anymore, you can erase it.

    Later I will explain the macro code which let you do your own macros.


    Next: How to use "Calibrated object files from CR2 files" macro

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