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Hi Neil,
My way:
Lay the telescope horizontal.
Put a white T shirt over the front of it- taped tightly & flat.
Use even thickness layers of cloth.
Block the rear of a Newt. with black cloth.
Turn the lights out.
Put your large computer monitor on the floor so that the middle of the monitor is at the center line of the scope.
Place it about 1 meter away
Make sure you make the monitor screen all white using a photoshop
pic made all white full screen.
Take flats with the camera at the same temperature as your light frames.
Make sure you go at least to 1/3 rd full well depth in the corners of the frame.
Adjust exposure time accordingly.
5 flats should be enough for each filter.
cheers
Allan
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