Aberrations in astronomy

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  • #574926
    James Dawson
    Participant

    I’m planning an online meeting for my local society on “aberrations in amateur astronomy” – the exact title is to be decided and will probab;ly include how to deal with these aberrations.

    I wanted to pick out the commoner issues with visual astronomy and astrophotography. 

    Topics I was thinking of talking about include:

    • collimation
    • thermal currents
    • coma
    • field curvature
    • vignetting
    • cone error

    What other issues and aberrations should I include? 

    Thanks.

    James Dawson
    Nottingham Astronomical Society
    https://www.youtube.com/c/NottinghamAstronomicalSociety/videos

    #584008
    Andrew Smith
    Participant

    Achromatic, tracking, field rotation. Eyepieces bring a new set kidney bean, astigmatism,  distortion….

    Regards Andrew 

    #584009
    Paul Leyland
    Participant

    The first Dobsonian I had showed serious spherical aberration.

    Worked just fine as a light bucket, which I what I wanted it for.

    #584010
    Robin Leadbeater
    Participant

    pinched optics, mirrors with turned edges

    #584011
    Ron Arbour
    Participant

    Insufficient Annealing of Optics

    #584012
    Graham Winstanley
    Participant

    Could be a long meeting, James!

    Atmospheric dispersion?

    Regards, Graham

    #584013
    Alan P Buckman
    Participant

    Hi James – You probably need to show how to measure qualitatively using Ronchi grating as a star test. There is an excellent book on the subject – Star Testing Astronomical Telescopes by Harold Suiter although he only uses intra-focal and extra-focal image appearance. Now that is an art!.

    Cheers

    Alan

    #584014
    James Dawson
    Participant

    Thanks all for the replies. Some very useful additions to my list.

    I’m planning to keep it simple (like me) and concentrate on the errors and aberrations which are common and [relatively] easy to resolve. I’ll get someone to talk about star testing to make people aware of the more advanced methods of testing optics available.

    Thanks.

    James

    #584015
    Andy Wilson
    Keymaster

    Another couple of thoughts. Fundamentally, even with a “perfect” telescope a star is a disc due to diffraction in the optics, and you rarely see performance at the diffraction limit as atmospheric turbulence blurs this disc.

    Cheers,

    Andy

    #584018
    James Dawson
    Participant

    Alan,

    I got a copy of this book maybe a year or two ago as part of a job lot of books. I flicked through it at the time and saw some equations and complicated graphs and decided it was too advanced for me, so I stuck it on a shelf… I’ve now looked in it in more detail on your advice and it is a remarkably accessible book. Yes there are equations and in places, it goes off on another level, but there is a good proportion of the book which is very helpful and informative. Thank you for making me get it off the shelf.

    James

    #584064
    David Arditti
    Participant

    A better title would be something like ‘Optical aberrations: identifying and treating them’.

    The word ‘aberration’ in general means something abnormal. So an ‘Aberrations in amateur astronomy’ would mean anything abnormal in amateur astronomy – like someone claiming to speak Venusian.

    David

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