Combining mosaic frames aligned against a StarGenerator master image

[RobF2]

Help please.  I've been playing with a 3x2 mosaic of RGB images taken with my QHY9.  The StarAlignment Register/Union-Mosaic mode with Frame adaption is impressive, but no matter how I combine individual images or groups of images I seem to end up with some geometric distortion.  

Tonight I've successfully generated a master image with StarGenerator and performed StarAlignment (Register/Union - Seperate) (with Generate Masks) for 3 of these images.  I gather the combination of these images is ideally done using Pixemath (Max function?) but this is beyond my current meager understand of PM.  Could someone please explain how I could combine these registered images?

I suspect I might be able to crop down the registered images then to a union mosaic function, but I don't really want StarAlignment having the opportunity to distort my nicely registered frames.  Any assistance appreciated.  I should add at this point in time I'm only working with the Red filter images.

Rob

[Astrocava]

Perhaps this thread will help you:

http://pixinsight.com/forum/index.php?topic=2715.0

Have fun!

Sergio

[RobF2]

Thanks Sergio - I did plunder that thread and others, but I don't yet have the smarts to figure out how to do this bit in PixelMath:

"Then use PixelMath to generate the whole mosaic with a maximum operation between all registered frames"

I'd would greatly appreciate a guru showing a screenshot of the correct expression loaded up into PM pretty please....
I'm pretty sure I'll end up going back to using DynamicAlignment too, but the learning curve has been steep the last few nights - I need another beer I suspect....!  
In the meanwhile I guess I'll have to grow up and get my head around PM workflow.....

[RobF2]

Like this maybe?