Granted I never shot with this lens but I couldn't resist posting this here since I never knew this existed before a week ago and thought some of you may appreciate the lens...
tsangc wrote:
That I own? 70-200mm f2.8L IS with a 1.4x
That I rented? 300mm f2.8L IS with a 1.4x
That I saw at a show? That Sigma 500mm that comes with its own LCD panel.
saaketham wrote: Do you have some samples of this Hubble Telescope setup?
The Hubble Telescope is a mirror-based design, the type of lens that everyone here seems to frown upon. I've considered getting myself a mirror lens to photograph the sky, but I just haven't bothered yet.
That being said, the longest for me is a Nikkor 300 f/4.5 AI-s.
saaketham wrote:
Which is the longest Canon (this word makes it ok to have this thread in this forum, I hope ) lens you've ever shot with? Other brands are also ok.
I'm going to answer your question in a literal sense...My longest lens is about 13 inches but if I retract the hood, it's closer to 10 inches.
Do you have some samples of this Hubble Telescope setup?
) lens you've ever shot with? Other brands are also ok. 
... 
?? Any samples? Please.