next up previous contents
Next: Geometric distortion Up: Other considerations Previous: Cosmetic defects


Thinned CCDS suffer from fringing, especially for observations with narrow passbands (<20nm) at wavelengths >500nm. This is not a problem for broadband images. Fringing in spectra flatfields out, but it is important to obtain a high signal-to-noise rati flatfield at every grating setting.

Tue Aug 15 16:42:46 BST 1995