Re: (ATM) RE: Super planetary
bruce mcmath (jbmcmath@intellinet.com)
Fri, 25 Aug 1995 17:45:25 -0500
>Certainly, on nights of sub par seeing, the operator of a large scope can
>flop a mask over the end and bring the F: down to the optimum... Very
>difficult to do the inverse however...
>Denny
>
Well if those who say there is no penalty, just no benefit, to having a
larger instrument than the seeing will allow to function at an optimum level
are right, there is no need to stop the larger instrument down. I don't know
the answer to this. The issue remains - is it always better, on the margin,
to seek better performance by focusing ones limited efforts or money in the
direction of size or quality. I think there is no debate that below a
certain size the bargain is in the direction of aperature. However, At some
point that may shift, if your interest is visual resolution - planets.
After all you can't flop a mask on and trade size for quality on those
nights when size is of no value any more than you can make it bigger on
nights when size would provide a benefit. If I can have for the same
investment a truly optimum 12.5" which will give me superior performance on
95% of the nights that are suitable for observing in comparison to a larger
but lower quality instrument that will out perform only on the other 5%
which should I choose?
It would seem, in short, that it is beyound doubt that the air puts cap on
resolution and as you approach that limit gains can only come from having an
instrument that more closely reaches the theortical limit available. where
is that trade off point? I would like to hear from those who have
experiance in this, it obviously is geographically dependant but still it
would be nice to hear from those with various experiances, and thoughts.