Daniel. You are using with me what you complain I supposedly did with Larry. I did not like Larry's review because it does not explain anything about the cause of the observed ranking.
In the other link http://www.cloudynig...php?item_id=506
you will see a completely different approach to explain why not being able to use more magnification (and you will see the Lick's scope was able to use much more). I did not want to throw any low bow. The same question (as you read the latter link) was asked them and they answered. Larry can elaborate a bit more on the point of magnification as well as on which were the causes (eg connecting star test to observed image quality).
Low magnification compresses image difference below the detection threshold of the eye (take the two Jupiters on the last column http://i45.tinypic.com/35le043.jpg
and move back from the screen until you re no longer able to see the difference. Then compute the equivalent magnification: it is about 150x). At low magnification the bottleneck is the Contrast Sensitivity Function of the eye, which incidentally you may measure. http://neurovision.b...onCSFchart.html
As for the"dark site" issue, I mentioned it because it is also a site with good seeing. It is a parking lot just at the bottom of these famous peaks in the North Eastern Alps http://www.lemiemont...me_Lavaredo.jpg
The site is 2320 m elevation, high enough to be above most of the planetary boundary layer (except if wind comes exactly form the peaks, which is rare) I did never measure seeing objectively, but my estimate is it to be sub arc second regularly.
Once I compared a TV 101 NP in parallel with a 16" dobsonian there. The 101 was able to achieve 250x of "roll-off" magnification. I stress term "roll off" the actual meaning of which is defined by Mel Bartels (scroll down) http://www.bbastrode...atemirrors.html
. Incidentally, in this other link http://www.cloudynig...php?item_id=506
what people do is just finding the roll-off magnification. I do no use useless magnification. I graually increse magnification until no new details are visible. So believe it or not roll-off is between 400 and 500x on that place (which means r0 approximately 20-25 cm, typical of good sites - where excellent sites have r0 = 30-40 cm.
Conversely at home, which is open countryside on a large flat land, roll-off is less but still often in the 300-400x. I am not the only one using such magnifications. A friend of mine, not far and in similar conditions makes pictures like these http://www.marcoguid...ve/20100922.jpg
There is however a trick in being able to use such high magnifications. It is controlling the boundary layer. My method is this http://autocostrutto...ng-mirrors.html
and Alexis made a nice comparisons of different methods here: http://www.cloudynig...ll/fpart/1/vc/1
I can telly you that it makes the difference. When I star observing images are often blurred at 160-200x, but then they gradually become crisper and crisper and the limit becomes the REAL seeing, which often means 400-500x on Jupiter. Of course a smaller and thinner mirror such as 10" 1" thick will be faster to equalize with the ambient temperature. Not so a 24" 2.25" thick unless some effective boundary layer control is adopted. But if that is used you get such high magnifications.
Anyway the discussion is not about how much magnification can be achieved by 24" but if 140x was enough. Larry does not explain why it was not possible to use higher magnifications. Here they explain http://www.cloudynig...php?item_id=506
Last comment is about seeing better in twilight. That is a problem related with the apparent size of the object. at 100-200x Jupiter looks 1.5-2.5 apparent degrees wide. If t stands onto a dark background the eye does not adapt to the brightness of the object. The object is like "over exposed" because the area considered bye the eye for "exposure adaptation" is wider. However things change when the object covers an apparent size of 5-8° (ie at 400x or more). In this case the planet is wide enough that the eye adapts to the brightness of ts surface without considering the foreground.
Finally, as for how many details you can see at low magnification you can never see more that your CSF permits. Take one picture of a planet (eg http://www.marcoguid...ve/20100922.jpg
) full of details and move at distance such as the apparent size correspond to the magnification you have in mind. Look with one eye. That is what you may at most see at that magnification. The real picture may have a lot more details, but the bottleneck is your CSF. If the picture remains crisp (ie we are below the roll-off magnification) at 250x, then there is NO WAY to see the same details at 135x.
Moreover: the roll-off magnification IS the quality of the image.
I just take it as high as I can until I can't take it any further. Whatever that number happens to be is what it happens to be.
You find the "roll-off" magnification. However ending up with 400x is a totally different story than stopping at 150x. By definition if you stop at 400x that means that with less magnification less was visible. Believe it or not, with exactly your same method, I got 250x with the TV 101 (on perfect seeing) and usually get much more with greater apertures.