Fringing in SOI
The images shown here are representative of the amount of fringing that can be expected in SOI imaging in the Bessell-I, SDSS-i and SDSS-z filters, at long exposure times (several minutes).
In the upper row we show super-sky flats obtained by median-combining a series of individual dithered exposures. The middle row shows typical science images obtained through each filter, and the lower row shows the result of correcting the science images in the central row with the super-sky flats containing the fringe pattern. The residuals are usually at less than the 1% level.
Of course, the amount of fringing will vary with sky conditions, which makes it more important that the astronomer plan their observation as a series of dithered exposures, so the appropriate correction frames can be generated, as shown above.
For more guidance and tips on how to carry out your observations with SOI to properly address finrging, go to the Evaluating and Reducing SOI Images page.