masking sensor marks

[Dave Lloyd]

I understand that dark frames eliminate hot pixels in stacked images but do light frames do the same for blemishes that may otherwise show up on a single image? I've a couple of very small specks on my dslr sensor and I wondered before I clean it if lights are a lazy way of masking them.

[Alien 13]

Light frames will correct for dust specs as well as general vignetting etc however the flats must be taken close to the time of the original image without any change to the setup, I have found this more difficult than it sounds especially if the dust moves during the imaging session.

Alan

[Dave Lloyd]

Cheers Alan, that's all I needed.

[ollypenrice]

Just a note on terminology but 'light frames' are, by convention, your actual pictures of the sky. It's flats that correct irregular illumination of the light path.

You may find that flats won't work for dust directly on the sensor because these pixels will probably have a near-zero reading and the correction, which is by division, might not work. Worth a try though. Failing that the clone stamp is your friend - or you could move the scope to take a few frames with the marks in a different place. You wouldn't need many, just enough to have a 'patch' to put under the main stack where the blemishes are. Put the shifted image underneath and just erase the blemishes from the top layer.

Olly

[Dave Lloyd]

Ah thanks for that Olly. I now know what flats are as well.

I really must get hold of M.E.P.C.