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Thread: Aperture vs seeing.

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    Default Aperture vs seeing.



    I remember past discussions concerning aperture versus seeing.
    I think the general idea was that, depending on seeing, that smaller (or larger) aperture scopes were less (more) beneficial.
    Was it to do with the size of the cells in the atmosphere and their altitude?
    Is there any new consensus on this effect?

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    Default Re: Aperture vs seeing.

    I'm not sure about a consensus among the membership here, but in my experience I have found that more aperture always helps up to the limitations of seeing. These limitations being either light pollution or seeing conditions. As you approach the current limitation, more aperture benefits less and less until there is no benefit from more aperture.

    I rarely use my 12" Dob at home in my moderately light polluted small town. My limit there is my 8" scopes (SCT and Dob) as I can reach as far with them as I can with the 12". But that is only IF the limiting factor is the light pollution. If seeing is limiting the conditions beyond that, I can reach just as far with a 6" or 4" scope, so they actually see more use there than the 8"ers.

    At the dark site, I do not have to deal with artificial light pollution, the ole' hateful orb and the seeing conditions are the only limiting factors. I can almost always benefit from more aperture there if there's no moon and conditions are fair. And now it comes down to how much scope I want to take and how much time I can spend. Regardless, the 25x100s ALWAYS go and many times that's all.

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    Default Re: Aperture vs seeing.

    Seeing typically kicks in at high powers. If you looking at the Moon, planets or splitting doubles if seeing is bad, (let's say 3") there is no point drugging out the big guns, since they will not provide more resolution over 80mm which has resolving power of ~2".

    For DSO it is more complicated, bad seeing is not as much issue here (unless you looking for a very small targets like PNs). For DSOs transparency is more important and you need to find right combination of exit pupil an power for each target.
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    Default Re: Aperture vs seeing.

    Quote Originally Posted by goldstar View Post
    I remember past discussions concerning aperture versus seeing.
    I think the general idea was that, depending on seeing, that smaller (or larger) aperture scopes were less (more) beneficial.
    Was it to do with the size of the cells in the atmosphere and their altitude?
    Is there any new consensus on this effect?
    My favorite answer - it depends.

    Bigz and Ozman have made that apparent.

    Cheers,
    JT
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