the blues are still way overexposed in those new flats. you want those histograms all in the middle of the display.
Rod,Glad I could help. Yes that is the type I mean, the one I use is this http://www.earlsmann.co.uk/sections/product/id/10 They can be cut to size and with a bit of DIY I made this:I used translucent plastic (2 sheets) to diffuse the light even more, the card cutouts are just to space the sheets, this fits on the end of the scope and I don't need to move the scope to take the flats. Works fine with the Astronomik CLS-CCD filter and Astrodon 5nm Ha, not tested with other filters yet. At f5 I give 0.3s exposure ISO100 with the CLS and 5 seconds ISO200 for the Ha.
Rod. I have used flats from various screens. More recently a Samsung Galaxy - with no deleterious effect. The streaks in your image are most likely produced by images too closely aligned during acquisition. The effect is pronounced with a small amount of drift between images. Irrespective of mismatched calibration frames, the effect can be eliminated by dithering all your images during acquisition by 10 - 15 pixels.Dithering will resolve a large proportion of your current difficulties. But dithering must be agressive with DSLRs.Flats - about 70 - 75% on your camera preview histogram is about right for starters.There is a tendency to get bogged down in the detail. Unless you dither your shots you will spend all your time post processing artifacts out, which can be minimized by basic acquisition techniques.
