[renormalised (Carl)]

On the issue of where to place the Bahtinov Mask, I usually place it on the naked optical tube ( i.e. minus the dew shield), although I did once do a quick test, placing it on the dew shield and it appeared to work/focus just as well. My dew shield is a homemade foam tube that easily slides off and my Bahtinov Mask sits more snugly on the naked OTA hence I focus with the dew shield removed.

That OTA should be ashamed of itself going without clothing in public!!!