NGC4565 and flat fields

This image of NGC4565 was taken under very clear sky conditions. It lies deep with in the constellation of Coma Berenices at a distance of about 42 million light years. Ay ten inch F4.8 reflector was used, with an Atik 383 mono CCD camera and PHD auto guiding. Astronomik RGB filters were used for the colour information with total exposure times of sixty minutes for each filter using five minute sub frames with matching dark frames. Flat field frames with matching dark frames were used for each filter. This reduces the effects of dust specks and vignetting showing on the CCD chip. The Flat field screen is shown on the end of the Newtonian:

This image shows an uncorrected and a flat field corrected image. Notice the correction for vignetting as a result of flat field correction.

The final processed image of NGC4565