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Old 03-02-2013, 02:23 PM
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alocky (Andrew lockwood)
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Join Date: Aug 2010
Location: perth australia
Posts: 1,291
I will buy into the limiting useful aperture debate. I use my 25" alongside plenty of smaller scopes in Perth. The atmospheric conditions here are generally average or worse due to the ubiquitous trade winds. Never has a smaller scope been able to operate at anything approaching the limiting magnification of the 25". On a good night I have run it at 800x and wished I had a shorter fl eyepiece.
Now don't take my word for it- as part of the research into the adaptive optics for the VLT the ESO found that resolution is atmospheric limited (ie rarely improves) above 30" or so in good sites, providing your local (ie thermal) conditions were managed.
I use my 25 for outreach events occasionally, and even under heavily light polluted skies a 25" provides brighter and clearer views than anything smaller. I have no idea how some of these myths propagate! I suspect it is more to do with people being too lazy to collimate carefully with the faster scopes, than anything inherent in the design. It's going to look horrible pretty quick at f3.

On the other hand - the ladder is something of a drawback, but at Perth Observatory we have had the public up on ladders since the 19th century without any debilitating injuries.
Andrew.
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