Are flat fields ever needed on lunar webcam images?

[michaelmorris]

As my lunar imaging slowly improves, and I get my mount to run ever smoother, it strikes me that on, on partcularly steady nights, vignetting and dust smotes might actually start showing up on stacked lunar images.

Is this a real worry or does the combination of atmospheric turbulance and drive errors inevitably make this concern unfounded? If this is a realistic worry, I presume that applying a flat field to each frame of the AVI prior to alignment should sort this problem out.

So here are my questions:

1) Are vignetting and dust smotes ever likely to make a noticable effect upon image quality for AVI-derived lunar images?

2) If they are, what is the simplest way to apply flat fields? I know I could convert every frame to a bitmap using IRIS or VirtualDub and then apply the flat field on a batch basis. Is there any software that allows one to apply a flat field to an AVI directly without going through the tedious, lengthy and hard-disk hungry process of conversion to BMPs and back?

[Milamber]

If you take avi's and stack them then you will have few problems - unless your tracking is too good. Odd I know, but if your image moves across or around the frame a bit then any bunnies and so on will be averaged out in the final stack.

[johnh]

My experience is that flats are only used to eliminate dust, vignetting is only an issue with large sensors eg dslr's and can be processed away easily with GradientXterminator or MaxIdl for monochrome.

2x or 5x barlows/powermates have a different effect on dust, if dust is small and sharp take a flat.

If dust is big and faint natural movement as mentioned by michaelmorris will be averaged away.

RegiStax allows darks and flats to be applied - converting hundreds of frames to bmp would be a pain - avoid this as its far to hard and takes too long. RegiStax automated calibration takes 5mins!

Hope this helps.