Dave- Regarding your question about aligning the mask : My closed tube would probably make this more difficult than a truss tube design, ----- Original Message ----- From: "David Dunn" <david.dunn@albertsons.com> To: <utah-astronomy@mailman.xmission.com> Sent: Thursday, February 27, 2003 8:52 AM Subject: RE: [Utah-astronomy] Goodwin Mask (short)
I have put curved spiders on three of the four telescopes I have built. I think that it is easier to build the curved spider than to built a vaned spider. I think that I understand the concept of the mask that sits on the mirror. How do you get it lined up on the mirror correctly? It would seem that if you didn't get it just right it wouldn't work.
Dave
-----Original Message----- From: David L Bennett [mailto:dlbennett@mac.com] Sent: Wednesday, February 26, 2003 11:10 PM To: utah-astronomy@mailman.xmission.com Subject: Re: [Utah-astronomy] Goodwin Mask (short)
Brent/Bob,
Is it possible that because the mask is, essentially, touching the mirror there is not the diffraction inherent with the spider and secondary obstruction? I mean, yes, there is a larger obstruction but isn't that obstruction basically diffraction free because of it's proximity to the mirrors surface? I would think that would be the only reason to place it upon the mirror as opposed to above the secondary mirror/spider where an aperture stop or apodizing mask normally would be placed.
David Bennett
On Wednesday, February 26, 2003, at 10:02 PM, Brent Watson wrote:
Bob,
This is an interesting idea, but I don't see that it would make the view any netter. The mask still acts like the spider, and in fact is worse because it is wider. It MAY get rid of the temperature effects mentioned in the article. I would be scheptical about it working, and would have to conduct several careful tests to see if it made an improvement.
Brent
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