why fast newtonians?

[bambuko]

The subject has been covered to a point where we started jesting , so perhaps I should let the sleeping dogs lie, but...

I have come across very interesting book: "Visual Astronomy of the Deep Sky" by Roger N.Clark (published by Cambridge University Press)

"...The typical handbook devotes considerable space to observing the Moon and planets, but when the subject of galaxies and nebulae comes up, it has less to say. Usually it just recommends that because these objects are faint, low power should be used.

     Such works have inculcated the idea among amateur astronomers that one should have a "richest-field telescope" and low-power eyepieces for deep-sky work.
     This concept seemed wrong to me. My impression at star parties in the dark skies of the Cascade Mountains of Washington state was that an 8-inch f/10 telescope gave a more detailed view of most obj ects than richest field telescopes of the same or even slightly larger aperture!

     This was one reason I built an 8-inch f/11.5 Cassegrain. Although I had started to build an 8-inch f/4.5, my opinions changed so much that I decided on the longer focal length partway through the project.

     I heard a few experienced amateur astronomers express the same thoughts-but none could give a good reason why high f/ratio telescopes seem to work better on faint objects...."

"...During research for this book I found the answer. The impression that higher f/ratios by themselves give a better view is largely wrong..."

"...The magnification used, not the f/ratio, determines what can be seen in a very faint object. A higher f/ratio telescope simply yields higher power with a given
eyepiece, and therefore it is more likely to be used that way..."

And... there is a lot more in this book that I found interesting, so rather than quote it all - I recommend that those who are interested borrow and read it.

Of course I am not trying to convince anybody about anything   and if you prefer and are happy doing your visual observation using fast reflector than that's fine.

I am just pleased to find someone else seeming to suggest that long slow scopes might have advantages for DSO, not just planetary observation.