1 1/4" Luminance Filter in EFW2: Individual Flat Sub and Flat Master (niteman1946)

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1 1/4" Luminance Filter in EFW2: Individual Flat Sub and Flat Master

Upper L/H: Line Profile of Individual Flat Sub image

Lower L/H: Individual Flat Sub image

Upper R/H: Line Profile of Master Flat image

Lower R/H: Master Flat image

Note how the Flat Sub curve abruptly drops at around 21k ADU to about 9k and 12k. This pattern repeats itself with the Master Flat curve. This abrupt change is referred to as "shoulders".

From discussions with knowledgeable folks on the Cloudy Nights forum, I have learned that ......

" ....... If a line profile through your images shows these "shoulders" you can assume the optical cone is being restricted by an aperture stop, possibly the filters. If the curve is smooth, even if it drops off dramatically in the corners, the light falloff is most likely a natural consequence of the telescope optics.

As a quick test, you could remove one filter and shoot through the empty filter position. If the vignetting changes (or not) you'll know if it is caused by the filter."

http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/6011701/page/4/view/collapsed/sb/5/o/all/fpart/2/vc/1

#6020892

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1 1/4" Luminance Filter in EFW2: Individual Flat Sub and Flat Master

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