[AstralTraveller (David)]

Jason,

As my grandmother would have said, 'you want your cake and eat it too'. You and most astronomers! Getting good wide-field views is fighting laws of nature. But, hey, what are laws for?

I think the best 'wide-field scope with aperture' may be a schmidt-newtonian. According to the manufacturers, a f/4 s-n has the off-axis coma of an f/5.6 newt.

Consider the effects of vignetting in any scope but particularly newts where the secondary size is often the limiting factor. But of course you want to keep the secondary diameter <25% of the aperture or you lose too much contrast (20% obstruction is best).

Remember the limitations of eyepieces. My 30mm 80 degree fov eyepiece is sold as the widest possible true field (in 2" barrels). On a 20cm f/4 that gives 3 degrees.

{EDIT: If the exit pupil is larger than your pupil not all the light will get into your eye and so in 20cm scope you will only 'use' 18cm or 15cm or 10cm.... of it's aperture. The diameter of the exit pupil is aperture/magnification and your dark-adapted pupil will be between 7mm and 5mm depending on age. This gives a usable minimum magnification of 28x to 40x. A 30mm eyepiece in a 20cm f/4 gives 26.7x and so is just usable.}

If you really want 5 degree fov why not get some good binos and a good stand and chair. I enjoy my 15x80 binos a lot.

Cheers