Well, it seems we are in agreement, but quite it's ingrained in advertising and even in articles that attempt to explain it get it wrong.
E.g.
http://www.dur.ac.uk/astronomical.so...ction=articles
Quote:
When using the telescope for photography, a "faster" telescope, that is one with a small f/ratio, will produce brighter images of extended objects. This simply means that you can get away with shorter exposure times compared to if you were using a "slower" telescope with a higher f/ratio.
For visual astronomy, the main influence the f/ratio has is that a "faster" telescope with a small f/ratio will deliver a wider field of view for a given eyepiece - this would help on some of the more extended objects such as the Andromeda Galaxy or star clusters such as the Double Cluster in Perseus.
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I put this in because it's a university teaching astronomy, yet they are misleading to the point that I would say they are plain wrong.
The second paragraph is correct, it also qualifies the conditions, i.e. the same eyepiece.
The first paragraph misleads more than it informs. It just makes a blanket assertion without qualifying what they mean.
I've found sites that specifically say that an 8inch F/6 is a brighter telescope than an 8inch F/10.
No qualifiers at all, just a blanket statement that implies lower F ratio means brighter image even on two scopes of the same aperture size.
Oh well.
I think this is one misconception that is too ingrained to be able to be changed.