Chris makes an interesting observation. On my original mask (bottom right) which Adam generously provided to the forum, there are 15 horizontal cuts of ~5mm width for my TEC160. This worked very well for me on first light - excellent focus and easy to see the center defraction spike move in and out of focus. Then David went over the top with his excellent mask generator so I created another mask for the 160 using that. Now, I'm the first to admit that I probably porked some of the data entries into the mask generator but the final product is different from Adams scalable mask. The generated mask has 11 horizontal cuts of ~8mm width which would allow slightly more light through the mask. The idea here is to get the best focus tool with the fewest number of cuts in the mask (I need to also create 80 and 100mm refractor masks). I've attached images of the two masks for comparison and I'll report back after comparing the two in my next imaging session.

Cheers and clears.

Ron