Re: ATM Apodizing Mask

[David Nicholls <nicholls@u030.aone.net.au>]

Peter,

Dick Suiter's web page Paul mentioned at
http://home.digitalexp.com/~suiterhr/TM/apodize.htm - in particular the
second PDF file link - has some good photos of how he made his mask,
which sounds a bit like yours.

I may try the "inverted spikey collar" mask and see if it works (somehow
I think that's a bad name).  It should be possible with a bit of deft
scissor work and stiff black paper, wrapped into a circle.

The lack of multiple criss-crossing fibers should make it a bit cleaner
than the standard apodizing mask, but the real question is will it work?

DN

On 10/10/2003 10:23 PM, Peter wrote:
> 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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-- 
____________________________________

David Nicholls
Nicholls Communications
dcn@dcnicholls.com
http://www.dcnicholls.com/
____________________________________