Hi Brend,
An excellent description of mirrored. My images are not mirrored, just in need of rotating. Another piece in the learning curve. And BTW I'm with you on this, there are no mirrors in the Cosmos!
As for all the other help, it would be difficult for me to fully express my appreciation; thanks to your help, I'm moving up the steep learning curve at an accelerated pace!
Going forward I will migrate to manual preprocessing and in the meantime I will always take Dark Flats so that option 3 will be available to me. A quick batch preprocessing followed by a decision to improve if the image warrants it.
So thanks again for all your help.
I am now bound for a weekend in a dark place in the Scottish Highlands, just up the road from Glasgow. It will be dark, but will the skies be clear?
Clear skies
Colin