Re: ATM Apodizing Mask

["Peter" <peter@kitgear.com>]

In hind site I should have taken a photo of the mask because it was very
different than your GIF image.  Yours is probably the ideal design.

The mask my friend had was made from ordinary window screen material (you
the black bug screen stuff). He used two layers, one masking the entrance
aperture to around the 50% zone, the second was glued to the first but only
going down around the 80% zone. In short the central region was clear
aperture, from 50% - 80% there was one layer of screen and from 80% - 100%
there were two. I'm sure that the zones need to be calculated for each scope
design.

I'll give him a call this weekend and see if I can take a photo. I'll also
see if he can find the original article describing the construction of his
mask.


Peter

----- Original Message -----
From: David Nicholls <nicholls@u030.aone.net.au>
To: <atm@shore.net>
Sent: Thursday, October 09, 2003 10:19 PM
Subject: Re: ATM Apodizing Mask


> I did a search on the S&T archive (apodize, apodizing, apodization) and
> found only a passing reference to a book (p94, Dec 1998).
>
> However, in my ancient and now gone collection of S&T that covered
> 1962-1969, I remeber an article that referred to a mask with a notched
> inside edge - I'm going to attempt to attach a GIF image of the idea,
> but if it's not allowed on this list, see
> http://www.dcnicholls.com/misc/mask.gif
>
> It would be simple to implement as drawn.
>
> Obviously it's not as extensive as the Suiter design and I don't
> remember the purpose of the original article.
>
> However, if the notches are sufficiently small, it might be possible to
> get some kind of interference effect... I've not even begun to think
> through the physics and the idea may be nonsense or irrelevant.
>
> DN
>
> On 10/9/2003 11:25 PM, David Harbour wrote:
> > Peter,
> >
> > I have seen at least one article about apodizing masks in an old Sky and
> > Telescope. But I no longer have my old Sky and Telescope magazines, the
> > hundred pounds or so of which almost caused me to tangle my PA-28's
landing
> > gear in high tension wires because I was taking off on only one magneto
on
> > one occasion. (Engage brain before flying airplane).
> >
> > But somewhere there must be an index to articles in Sky and Telescope, a
> > sort of archival directory by subject or topic category. Hope you can
find
> > that article, I am sure that I saw it and read it, maybe about a hundred
> > years ago or so, and in fact, remember how to make a rather effective
one.
> > But don't trust my memory; surely someone else will have that issue or
> > issues and will respond.
> >
> > Davey
>
>
> --
> ____________________________________
>
> David Nicholls
> Nicholls Communications
> dcn@dcnicholls.com
> http://www.dcnicholls.com/
> ____________________________________
>


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