First and foremost observing love: naked eye.
Last but not least, telescopes.
And I sometimes dabble with cameras.
Quote:.You never get to the .5mm exit pupil of legend (equal to 2x the diameter in mm or 50x diameter in inches) but you're forevermore restricted to 0.67 minimum exit pupil. You know what? not a badidea, not at all.
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Quote: Bigger apertures always show fainter objects -- and finer details in small objects -- than smaller apertures.Seeing permitting, an ideal eyepiece collection lets you get to exit pupil of 0.5 mm or smaller. However, this places no constraints on the telescope, since Barlows can be used to achieve arbitrarily high magnifications.Although in theory there are cases where a 7-mm exit pupil will allow you to see faint objects invisible at higher magnifications, such objects are in fact vanishingly rare. In practice, a 4-mm exit pupil is ample for the faintest objects and the most aggressive filters.Nonetheless, all other things being equal, focal ratios slower than f/8 are undesirable, because they make it hard to achieve adequately low magnifications. Nonetheless, since most observing is done at exit pupils of 2.5 mm or less, this turns out not to be a huge limitation in real life. Moreover, many slow scopes can be fitted with focal reducers -- a standard commodity for SCTs.There are objects such as the Pleiades that are simply too large to view in big telescopes. That's why small refractors (and their extreme, hand-holdable binoculars that operate at 10x or lower) fill an important niche.Any telescope is better than no telescope. And given sufficient skill, any observer will get great results with any decent telescope.
Quote:Seeing permitting, an ideal eyepiece collection lets you get to exit pupil of 0.5 mm or smaller. However, this places no constraints on the telescope, since Barlows can be used to achieve arbitrarily high magnifications.
Orion XT12i with Swayze-refigured primary & Protostar secondary
Televue NP101 refractor
William Optics Megrez 90 refractor
Universal Astronomics Deluxe Mounts
15" Obsession #1603 AstroTech AT66
Quote:Someone wiser than me told me once that the magnifications used in a scope were, "Low enough to avoid the flotsam in the eye and high enough to avoid astigmatism".
Quote:I don't know if this has been discussed before but I've been reading this:http://www.rocketmime.com/astronomy/Telescope/SurfaceBrightness.html
Quote:But in all other cases, where resolved, extended objects--and just as importantly, the sky glow itself!--are concerned, such a statement is utterly wrong. This is because the optical principle known as etendue preserves surface brightness, the latter of which depends on the exit pupil, or the eye's pupil, whichever is the smaller.
A man is a small thing, and the night is very large and full of wonders.
Quote: However I still don't understand it in this context. Can you or someone find simpler words to digest?
Quote: Also, thinking about Mr. Ferris's 2 degrees, I don't have a telescope/eyepiece combination that even reach 2 degrees of FOV. How come I can see so many Dso's in that telescope?
Quote:Ok so M1, would be close to 20, and the sky would have to be darkened to 19 which means a 1.585 increase in magnification but the size has to be increased by 2.37, so if I call all that a 3x increase in magnification now the sky is roughly 20 and the size must now go to 26 but the 3x only got me to 24...I feel like I'm chasing my tail here... Is there a short cut?
Quote: The only way to move to the right is filters?oh sorry I know, travel to a better site or use larger aperture of course. Any other way?
Quote:Nils Olof Carlin ... seems to disagree about Clark's interpretation in what appears to be the threshold size.