FreeLists / az-observing / [AZ-Observing] Re: [Fwd: Re: Mars Sunday night]

["Stanley A. Gorodenski" <stan_gorodenski@xxxxxxxxxxxxx>]

Although aperture stops will reduce resolution it also reduces some of poor
seeing. I think the issue is when will the advantage gained from aperture
stopping by 'improving' seeing be outweighed by the disadvantage of reduced
resolution.
Stan


>  Have never been a fan of aperture stops. In some scopes of short FL, this
> may be ok, but more often it seems like a waste of aperture paid for. If its
> a good mirror or lens, it should be possible to observe with all of it, using
> filters to control the light. I have used such masks in places with extreme
> poor seeing, only. Too often, a club gets a person who pushes these devices,
> and everone is wasting glass they bought and carry outdoors. I was using a
> club scope back in New England 15 years ago for Mars at its last great
> opposition. The image looked dull and lacking color. I later started to
> view deep sky and saw the same result. I tilted the tube down (It was a big
> Clark and Sons 9" f13 1905) walked to the lens end expecting to find a layer
> of dew and found instead someone had previously used the scope and left a
> 5.5" stop on it! Removed that item and all was well, and Mars was, as is now
> a very attractive view. Resolution reduction is not the way to go.

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