Maximum Useful Magnification

I've read on the Televue website that the maximum useful magnification is limited by the atmosphere to about 300x. Is this is true?

What is the highest useful magnication in a 10" dob for different objects like planets, lunar, galaxies etc?

The atmosphere is a variable filter. Sometimes it ruins the image at relatively low powers, and sometimes it doesn't. There's also the matter of getting enough retina involved to easily make out fine detail. I routinely use about 362x in my 10" Dob on targets like the moon and Saturn. These targets tend to have plenty of contrast to spare for most detail. Jupiter and Mars tend to look better in the 200x-275x range. Going higher seems to drop the contrast too much. As for maximum, I sometimes use 50x per inch with the moon and with globular clusters. I have gone higher, but have rarely (never?) had a better image than at about 500x. For one thing, I have problems with floaters.
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Mike

To me, power depends on three things!
Seeing, good optics and a well collimated scope.

For a 10" Dob in 8+ seeing, thats collimated, with super optics, should handle 350x 850x.
But for most people i would say around 200x 400x should do fine. Any fast scope, that's not collimated will really show its bad side once you get the power above 200x...

I've had many fast 10" scopes, and the ones with bad optics wont handle high powers!

ChasP.

Planetary detail will most likely be limited by the atmosphere more than your telescope, especially in the 8 to 10 inch range. But what the upper limit is will be dependent on your atmosphere. Where I live in New England I have never had a night that really was improved above 220x. (280x was still good, but I could not honestly say that I could see more at 280 than at 220.) Those nights are few and far between around here. I often get more pleasing views (not more visual information) in my 5" than in my 8", but on a really good night apeture certainly rules. Observers in Florida and Arizona do much better than that on a regular basis.

You might enjoy reading some of the short articles on Newtonians on Bob Royces web site (rfroyce.com). He really likes 10" reflectors, and he writes clearly with a lot of common sense.