Flats issue

[bottletopburly]

I’ve been plagued with getting good flats with primarily my 8” Newtonian I just don’t think using the El panel they work correctly on the vignetting , I just came across a blog http://astronomy.colinrmitchell.com/index.php/2020/06/15/taking-flats-with-a-large-newtonian/ where this chap seems to have found the answer  by using a projection screen and a light box to illuminate screen , now a few years back I used to point my scope at the living room window for flats and I can’t seem to remember having issues, the window is probably 20ft away So next time I use the Newtonian  I’m going to re try this method and see if this works better than the El panel  and maybe create a custom park so it centres on the window.