Thanks guys, I think my prime focus, long focal length imaging through an F12 optical tube are over! It was so sweet to not have star trailing and guide star issues with the 400mm F5.6.
I’m not sure if the “central hot spot” is a hot spot/vignetting artefact or simply the Sagittarius star clouds? Next time, I’ll take some Flats to see what results I get.
Mike – the 400mm F5.6 cost me just over $1400 from
Discount Digital Photographics and it pairs up nicely with the Canon 40D. Remote Live View running on the notebook was an essential aid for manual focusing, absolutely indispensible IMHO.
Cheers
Dennis