Your response simply will put me in a permanent doubts then.notFritzArgelander wrote: ↑Sun Oct 27, 2019 11:27 pmWell since this was addressed specifically in response to me, I'll answer. You are going by "what you can see" which is fine if that is what gives you confidence. But there are other criteria such as objective measures of telescope performance For planetary observation light is almost never a problem but one is more concerned about 1) resolution and 2) contrast on small objects. Those are completely different considerations.TareqPhoto wrote: ↑Sun Oct 27, 2019 10:13 pm
Ok, let me put it this way then.
I visited 2 places or centers of Astronomy in my country, and they do visual even for public, one placing C9.25, and the other placing Meade 10" SCT, i looked through both of them, both are amazing, BUT, none impressed me enough, i mean they are almost the same view or even less than my Mak, my Mak is sharper and their SCT are brighter, that's all, so i couldn't feel the difference, so in imaging even with larger aperture advantage i don't think both of C9.25 or C11 will impress me, i already saw hundreds or thousands of results from C11 on the net, none of them changed my mind from C14 or 16" Dob results, in fact even 12" Newtonian is better result than C11 from what i saw, means i have to forget about 9" or 10" or 11" and start from 12", and because i will have 20" Dob later so i feel i will not go with 16" or 14", but 14" is still in list but less priority, 12" is shining more in my list and head, but i have to wait and see, i may buy anotehr mount, or i may risk with 12" on EQ6, or maybe i can increase the 20" scope so i can buy an EQ platform and use that, but nothing is yet confirmed, but the only confirmation i have is that 9.25"/11" are not in list and also 12"/14" SCT are not in list, if i must buy a new mount for 12" SCT or 14" SCT then it is very affordable for me to get 12" Newt and another mount then, i can save more by this.
Your point about is C9.25 and C11 is very correct, i should start with that actually last year so maybe i won't think about larger scopes yet, but my mistake [maybe not] is that i went with 7" Mak and 8" Newt, and results telling me that 10" and closer aren't gonna cut for me on planetary, 12" is also not much, but it is the largest cheaper options i can get right now later.
Now I don't like standard SCTs for visual use. They always appear "soft". However aplanatic SCTs like the Celestron Edge HD and Meade ACF are something else again. They are full up to giving crisp visual views like a refractor or Maksutov. They also cost more. But I have to say that while the plain vanilla SCTs don't hold a candle to a Rutten-Maksutov the aplanatic SCTs are worthy rivals (Edge, ACF).
Nevertheless Damien Peach's results show that at the right site a standardSCT does splendidly at planetary imaging. Visual appearances should not be taken as an adequate indicator of what to expect when imaging. I know this from experience studying and working at a university observatory in the US. For imaging, one must go by the numbers. So what do the numbers say about 1) resolution and 2) fine contrast?
1) Resolution
Without an atmosphere, resolution is determined by theaperture . The resolution is inversely proportional to theaperture . For most places on Earth resolution is limited by the atmosphere so that 10"aperture or 0.5 arc second of resolution is about all you will ever get. Board member Luc CATHALA gets exquisite lunar images with his large Newtonian optic because he is fortunate to have a site with better than average seeing. For most places on the planet for almost all days anything larger than 10" gives no resolution gain.
2) Fine contrast
Visually folks note that the large central obstruction of SCTs diminishes contrast on large objects. However the obstruction increases fine contrast.
The quantitative measure of fine and coarse contrast performance is given by the modulation transfer function or MTF.
https://www.telescope-optics.net/mtf.htm
The effects of a central obstruction are shown in figure 104 at the following link.
https://www.telescope-optics.net/obstruction.htm
The green line in the graph shows the MTF of a perfect unobstructed optic. The orange line shows the MTF of a perfect 32.5% obstructed optic. Notice that for low frequencies the orange line is below the green line showing the loss of contrast for large objects compared with the perfect unobstructed optic. However above 0.6 in frequency see that the orange line is above the green line showing that for planetary contrast discrimination an obstructed perfect optic is BETTER than an unobstructed perfect optic.
I paid for Damian Peach videos on Patreon, and i can't really judge if his comments or videos are paid for him to give what he said or he was honest, but i believe even Damian can do much better with 14"-20" Newt/
Again, you said most of the world or maybe the whole planet but then there are people using largest scopes such as 14" or 16" or 24" or 30", imaging isn't my only goal although it is, but i want to see the power of visual with largest
I follow what i see by my eyes, not what i read from studies and analysis and charts and lines and curves, and i saw the best planets images so far in my life are from Space telescopes followed by 1 meter scopes and then i only say from amateur scopes up to 20", i liked from 20" then 18" then 16" then 14" and then 12", the problem is people didn't use their 16"-20" in same conditions as Damian and Go did, if they did then i am sure they won't be any less than C14 world known imagers, so i follow of what i saw as results from those, and it tells me simply that "
I have enough time to decide until next year, I can't afford premium
Bottom line, all what you said is respected and understandable, but sometimes i go with something else more than just facts or studies or theories, many put Damian as a reference because of his results, but look at his results, Barbados and 1meter scopes are talking, while his images with C11 or C14 in UK isn't any special to be honest, so i am not that kind of guy who just go with one eye, i looked at all Damian results from the past on different planets, only his images from 1 meter and C14 in Barbados standing out, while from UK for example i saw better results than those, so i don't know if i should believe Damian in his videos or you or others or my eyes.