Flats and Bias Frames

[Taff]

Hi' Can anyone explain to me what is the difference between Flats and Bias frames.And how do they help when taking captures Thanks.Mark

[jgs001]

Martin posted up some great info yesterday on bias frames. Worth checking that thread Mark, but they remove the bias data the sensor creates. As for flats, I don't know all they do, but removing vignetting, dust and dirt in the imaging train is part of it. The DSS help recommends setting the camera in Av mode and letting the camera expose for the flat, it works for me.

[MartinB]

Here's the primer on bias http://stargazerslounge.com/imaging-tips-tricks-techniques/76972-bias-frames-image-calibration.html

If you take an image of an evenly illuminated plain white surface and brighten the result it is more than likely that your image won't be smooth and white. you might have vignetting, also marks from specks of dust which are greatly enlarged. Because astro images tend to be very dim, even after long exposure we have to brighten them, normally by stretching the histogram. These irregularities then affect the image.

By taking a flat, which is essentially a picture of an evenly illuminated surface smooth surface we can use software to calibrate our astro image against this flat thus removing the irregularities.

[Taff]

Thanks john for your infor.Mark