Loading ...
Sorry, an error occurred while loading the content.
 

Re: [ccd-newastro] Splitting Stars/Viewing

Expand Messages
  • Alain Drozd
    Hi Rick, for seeing, take a look to Marc Sylvestre site page concerning determination of seeing by counting stars. It looks very accurate at:
    Message 1 of 3 , Jan 4, 2001
      Hi Rick,

      for seeing, take a look to Marc Sylvestre'site  page concerning determination of seeing by counting stars.
      It looks  very accurate at:

      http://www.astrosurf.com/universia/Anglais/index1anglais.htm

      Alain
      Astro: http://adrozd.free.fr
       

      "Foster, Rick" a *crit :

      Hi Ron and CCD'ers

      I hope this is not too far off topic or not appropriate for this list.
      Please let me know if it is.

      One other question, How do you determine seeing level?  Is it done by
      whether or not you can see a star of certain magnitude? Is the star
      twinkling or not?  If so, what is good seeing (assuming one has 20/20
      vision)?

      Thanks and clear/dark skies,
      Rick Foster

    • Ron Wodaski
      From the Celestron web site: For telescopes this is referred to as Dawes limit. It is the ability to separate two closely-spaced binary (double) stars into
      Message 2 of 3 , Jan 4, 2001
        From the Celestron web site:

        "For telescopes this is referred to as "Dawes limit." It is the ability to
        separate two closely-spaced binary (double) stars into two distinct images
        measured in seconds of arc. Theoretically, to determine the resolving power
        of a telescope divide the aperture of the telescope (in inches) into 4.56.
        For example, the resolving power of an 8" aperture telescope is 0.6 seconds
        of arc (4.56 divided by 8 = 0.6). Resolving power is a direct function of
        aperture such that the larger the aperture, the better the resolving power.
        However, resolving power is often compromised by atmospheric conditions and
        the visual acuity of the observer."

        Note that Dawes' limit is based on two stars of equal magnitude; if the
        stars have different brightness, you may not get an accurate assessment. It
        has been shown that in practice, modern telescopes often exceed Dawes limit,
        especially at the high end.

        Here are some links that you might find interesting:

        http://www.umanitoba.ca/faculties/science/astronomy/courses/astro280/98R/Mik
        e/calculations.html

        http://www.atmpage.com/calc.html
        http://www.ast.cam.ac.uk/gallery/observing/m13.html
        http://www.seds.org/billa/lm/rjm.html
        http://www.njaa.org/meteors/maglimit.html


        Ron Wodaski
        The New CCD Astronomy Book
        web site: http://www.newastro.com



        -----Original Message-----
        From: Foster, Rick [mailto:rick.foster@...]
        Sent: Thursday, January 04, 2001 7:36 AM
        To: 'ccd-newastro@egroups.com'
        Subject: [ccd-newastro] Splitting Stars/Viewing


        Hi Ron and CCD'ers

        I hope this is not too far off topic or not appropriate for this list.
        Please let me know if it is.

        I would like to determine the relative resolution capabilities of my scope.
        I understand that to a degree the smaller the distance between two stars you
        can discern (minus the seeing level) the better the optics of the scope are.
        Does anyone have the relative split in distance a scope should be able to
        split by aperture size? I have a list of stars that are close together with
        their separated values but I do not know to what level I should be able to
        split. I have seen reference in books that you should be able to split
        these two stars in say a 6". I have a LX200 10", F10. It does not appear to
        grossly out of collimation yet (the secondary in an out of focus state is
        centered).

        One other question, How do you determine seeing level? Is it done by
        whether or not you can see a star of certain magnitude? Is the star
        twinkling or not? If so, what is good seeing (assuming one has 20/20
        vision)?

        Thanks and clear/dark skies,
        Rick Foster

        To unsubscribe from this group, send an email to:
        ccd-newastro-unsubscribe@egroups.com
      Your message has been successfully submitted and would be delivered to recipients shortly.