Flat Frame Calibration Astrophotography Example with M13

Flat Frame Calibration

Flat Frame Calibration

A couple weeks ago I built a flat frame light box for my telescope so I can take these really important images so that imperfection (dust, etc.) in my telescope and CCD camera are subtracted from the frame.  At the most basic level, flat frames are used to correct the vignetting and uneven field illumination created by dust and imperfections in the optical train.  In the example above, the photo on the left is not flat frame calibrated and you can see dark circles in many places on the image.  These imperfections are dust motes.  The photo on the right has been calibrated with flat frames, serving two very important purposes:

1.  Removing dust motes

2.  Evening out the field around the corners of the image

Here is the final LRGB image of M13 that is both dark and flat frame calibrated:

M13 Globular Cluster in Hercules

M13 Globular Cluster in Hercules

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