[Bassnut (Fred)]

I’ve come to considering a wider FOV via a bigger cam, or mosaics with what I have (ST10).Mosaics are a severe time consuming exercise, at least I thought so until I looked into the options.
Assuming in my case, that the most exposure time is with Ha (both in narrowband and Ha as Lum in LRGB), it was most interesting to see how a larger chip would influence exposure time for a given approximate image scale and FOV.
Here’s an analysis of 2 options available with a 10" scope, using a 0.67f FR to try and keep the images scales roughly equivalent.
On a 10" scope
Chip QE at 700nm, pixel, image scale, FOV arc min
KAF 3200 (ST10) 80% ,7um, F6 0.93, 23 * 34
KAF 11002 (ST11k) 25%, 9um, f9 0.82, 37 * 55
KAF 16803 40% ,9um, f9 0.82, 56 * 56
To get roughly the same FOV as a KAF 11002 (ST11k) would require 4 panels from an ST10, a KAF16803 would require 6 panels. Doubling the f ratio requires 4 times the exposure for the same flux, so the FR in this case from f6 to f9 would double exposure time.
To get the same flux and FOV then from an ST10 mosaic with 1hr Ha requires these exposure times with multiple panels.
KAF 11002 (ST11k) 4 panels of 1hr =4hrs on an ST10 at f6 to equal a single panel of 6.2 hrs at f9 .
KAF 16803 6 panels of 1 hr = 6 hrs on an ST10 at f6 to equal a single panel of 4 hrs at f9.
The ST11k then requires more exposure time for the same result, and the 16803 less, but im not convinced the diff is worth the money. Certainly mosaicing is not the horror one would expect.