OK, here is an image of Mars, with alot of detail, I super imposed a grid. Mars is sized with the grid to represent it at opposition, about 25 arc seconds. The grids are 1 arc second square. I looked up telescope resolutions, they are as follows..
90mm= 1.3 arcS
4 inch= 1.1 arcS
10inch= .45 arcS
So in theory and perfect atmosphere, a 4 inch could discern details the size of each square a 10 inch could discern details to about 1/2 the size of each square.
Of course this also depends on the contrast of the features and scope also. This at least should give us all an idea of what we could see. After doing this I can see that the atmosphere is really a major limiting factor for most of us. I also can see why people with 4 and 5 inch apos are seeing Mars so well, as most of the time a large scope is not even getting close to it's max capabilities so the apo's crips views and high contrast are beating the veiws of the larger instruments higher resolving power that is not able to be taken advantage of.
I got started on this after all those threads about aperture and seeing, then I read Ed Tings review of the Portaball 12.5 inch, even though it had 1/27th wave optics AND more aperture, he said the two apos that were there that night still beat it on the planets, I infered from him that the ability to see lower contrast outweighed the resoving power of the portaball that night.
So I think atmosphere really is our number one enemy, not our scopes!
Take care!
Ron
90mm= 1.3 arcS
4 inch= 1.1 arcS
10inch= .45 arcS
So in theory and perfect atmosphere, a 4 inch could discern details the size of each square a 10 inch could discern details to about 1/2 the size of each square.
Of course this also depends on the contrast of the features and scope also. This at least should give us all an idea of what we could see. After doing this I can see that the atmosphere is really a major limiting factor for most of us. I also can see why people with 4 and 5 inch apos are seeing Mars so well, as most of the time a large scope is not even getting close to it's max capabilities so the apo's crips views and high contrast are beating the veiws of the larger instruments higher resolving power that is not able to be taken advantage of.
I got started on this after all those threads about aperture and seeing, then I read Ed Tings review of the Portaball 12.5 inch, even though it had 1/27th wave optics AND more aperture, he said the two apos that were there that night still beat it on the planets, I infered from him that the ability to see lower contrast outweighed the resoving power of the portaball that night.
So I think atmosphere really is our number one enemy, not our scopes!
Take care!
Ron
Attached Image: