Surface brightness vs aperature vs sky glow

Tony Flanders has put together a website on Messier Objects that is worth a view. Even better than the Messier catalog that he's got, are some essays on Surface Brightness, Telescope Limiting Mag and Aperature vs. Sky Glow. Throughout, he compares how a TV Ranger stacks up against a 178mm newt on some common objects in urban, suburban and rural sites of varying light pollution. At the bottom of the article on Aperature vs. Sky Glow there are some artists renditions of aproximately what M31, M38, and M42 look like through these scopes. These articles and their accompanying pictures and charts are worth reading. I especially recomend them to folks who are undecided about what aperature scope to get for their viewing conditions. Tony's focus is on faint fuzzies, not planets, but there is plenty of info there to start lively debates on a whole range of topics.

http://mysite.verizon.net/vze55p46/index.html

Just click on the topics to the left, and click on various hyperlinks throughout.

Mike Swaim

Interesting, and about as it is. Tony Flanders made a good point, that dark skies can be more important than aperture size for certain object types (i.e. galaxies in general). A 4" at 21 mag/arcsec sky would likely show about as much as a 16" at 18mag/arcsec sky. Another thing is that large apertures use in general lower relative magnification, which makes sky background brighter, so that their actual advantage is less than what the nominal light-gathering figure implies.

But for some other object types aperture size is more important factor. Large apertures have also resolution advantage, but only on those objects that can take higher magnifications (this also requires good seeing).

Thanks for interesting and informative reading.