In the previous lecture we saw how to use bias frames, dark frames and flat fields to correct our raw CCD images and prepare them for accurate scientific work, like photometry. In this short practical we will use astroImageJ to process a series of images of M51 taken using the department's 10-inch robotic telescope, ROSA.
AstroImageJ is already installed on the lab PCs. Should you want a copy for your own machine, it is available for download. A detailed and helpful manual is available. If you encounter difficulty, or do not understand a setting, check the manual.
To open AstroImageJ, double-click the file C:\SharedFolder\astrolab\AstroImageJ\ImageJ\AstroImageJ.
You will need a copy of the data. The data files are located at C:\SharedFolder\astrolab\M51. There are 18 images of M51 in each filter. Also in this directory are three bias frames, three dark frames and three flat fields in each filter.
You can work on the data in the SharedFolder. However, this folder is local to the PC you are working on now. If you want to keep files from this practical to use later, you will need to copy those files to your U: or M: drives. There is just over 100MB of raw data, so make sure you have enough free space before doing this!
Data Processing with astroImageJ
Before you start any data processing job, you should make sure you have the calibration files you need.
Task 0: Open astroImageJ and open the file named "M51_B_001.fit". Look at the FITS header metadata by choosing Edit > FITS Header. Note the filter used and the exposure time. What calibration files will you need for this image? If you're unsure, try and ask.
Close this image and the FITS header window.
Data processing in astroImageJ is performed the data processing window, shown in figure 79. Your next task is to familiarise yourself with this window.