Back to Home

ATM Forum Message

Forums: Atm · Astrophotography · Blackholes · Blackholes2 · CCD · Celestron · Domes · Education
Eyepieces · Meade · Misc. · God and Science · SETI · Software · UFO · XEphem
RSS Button

Home | Discussion Forums | Amateur Telescope Making | Post
Login

Be the first pioneers to continue the Astronomy Discussions at our new Astronomy meeting place...
The Space and Astronomy Agora
Re: Foucault Testing 8" F/4.5

Forum List | Follow Ups | Post Message | Back to Thread Topics | In Response To
Posted by JimS/">JimS on February 10, 2000 00:54:48 UTC

: : : Sounds like you have a severely rolled down edge if you're talking about the last section. The relative distance from the center gives the difference in Center Of Curvature of the various zones. You should get to a point when traveling out where the left and right sides dim equally. Take as the point for the comparision about 1/4" in from the edge as the edges themselves do generate a nice bright diffraction of light on the left side. If you made a mask, you will also notice that all of the edges of the mask do tend to be very bright. Again this is diffraction at work. You do indicate that the Ronchi Test indicates a good surface which is kind of in disagreement with what the results you're indicating for the Foucault test. Or are you trying to get the diffraction image to work like the rest of the mirror? : : : As far as the slit is concerned, I prefer the slitless method as you don't have to worry about a slit width and can use a .003"-.005" slit if you desire and you don't have to worry about alignment of the slit to the KE.

:I think your right, the edge does some strange thing with the Screen close to the COC of the center. I cant get just 4 or 5 lines,what I see is a "pile-up" of lines along the edge maybe 3 or 4 thightly packed lines in the 85% zone and three widely spaced lines across middle 70% of the aperture.

Follow Ups:

    Login to Post
    Additional Information
    Google
     
    Web www.astronomy.net
    DayNightLine
    About Astronomy Net | Advertise on Astronomy Net | Contact & Comments | Privacy Policy
    Unless otherwise specified, web site content Copyright 1994-2020 John Huggins All Rights Reserved
    Forum posts are Copyright their authors as specified in the heading above the post.
    "dbHTML," "AstroGuide," "ASTRONOMY.NET" & "VA.NET"
    are trademarks of John Huggins