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  1. #1
    Michelle Stone's Avatar
    Michelle Stone Guest

    Default Should I buy nebula filter for my 120mm refractor?



    I'd go with the O III filter. Hydrogen rich nebula will never look better.

    Michelle Stone
    Custom Telescopes by Plettstone
    http://www.plettstone.com/telescopes


    anteperkovic@vip.hr (Ante Perkovic) wrote in message news:<f7ead98e.0309091023.34fc3a68@posting.google. com>...

  2. #2
    David Knisely's Avatar
    David Knisely Guest

    Default Should I buy nebula filter for my 120mm refractor?

    Hi there. You posted:


    Well, the problem is that the brightest Hydrogen emission line (H-alpha, at
    6562.8 Angstroms) is so far into the red that the human eye has difficulty
    seeing that kind of emission. The OIII also eliminated the effect of the
    second brightest line (H-Beta at 4861 Angstroms), so for hydrogen emission
    nebulae in a small telescope, the OIII isn't exactly the filter of choice
    (although it certainly can be used in smaller instruments). For planetary
    nebulae which have the strong OIII emission lines, the OIII overall is the
    better filter, but for smaller apertures trying for diffuse emission nebulae,
    the UHC (or another narrow-band filter) can be somewhat more useful. The
    broader bandwidth of the UHC will also not dim the stars quite as much as in
    the OIII, so it will be a little easier to "navigate" areas, especially in
    smaller apertures. In fact, there are some nebulae which are hurt by the OIII
    over the UHC or H-Beta filters. On the Cloudynights web page
    http://www.cloudynights.com is an article comparing the performance of various
    filters on over 80 emission and planetary nebulae, and it can be a useful
    guide to which filter to use.
    --
    David W. Knisely KA0CZC@navix.net
    Prairie Astronomy Club: http://www.prairieastronomyclub.org
    Hyde Memorial Observatory: http://www.hydeobservatory.info/

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  3. #3
    Shneor Sherman's Avatar
    Shneor Sherman Guest

    Default Should I buy nebula filter for my 120mm refractor?

    Hi Michelle,
    I think perhaps the H-Beta might do better on hydrogen rich nebulae.
    Clear skies,
    Shneor Sherman




 

 

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