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  1. #11
    Sam Wormley's Avatar
    Sam Wormley Guest

    Default Equivalent scopes (or binocs) to match Messier telescope(s)



    Chris L Peterson wrote:

    Messier's telescopes
    http://www.seds.org/messier/xtra/history/m-scopes.html

    1. Ordinary refractor of 25 foot FL, Mag. 138x

    2. Achromatic refractor, 10.5 foot FL, owned by M. de Courtanvaux, Mag. 120x

    3. Achromatic refractor, 3.25 foot FL (Dollond), owned by Duc de Chaulnes, Mag. 120x

    4. Ordinary refractor of 23 foot FL, Mag. 102x

    5. Ordinary refractor of 30 foot FL, owned by M. Baudouin, Mag. 117x

    6. Campani refractor, owned by M. Maraldi, Mag. 64x

    7. Gregorian reflector ('Short') 6 feet FL, owned by M. Lemonnier, Mag. 110x

    8. Gregorian reflector 30 feet FL, 6 inch aperture, Mag. 104x

    9. Newtonian reflector 4.5 foot FL, Mag. 60x

    10. Refractor 1 foot FL, 3-inch aperture, owned by M. de Saron, Mag. 44x

    11. Refractor 19 foot FL, of the Paris Observatory, Mag. 76x

  2. #12
    CNJ999's Avatar
    CNJ999 Guest

    Default Equivalent scopes (or binocs) to match Messier telescope(s)

    Ok, I'll state again that readers should not confuse the often repeated
    listing of telescopes Messier employed for all sort of observations,
    including follow-up examinations of "his objects", with the instruments
    he actually used in his successful search for comets.

    Literature directly pertaining to his discoveries indicates on a number
    of occasions "a 1-foot telescope" was used. Refractors of such
    focal-length of the period generally had apertures of around 2 inches
    or slightly less. Perhaps even more specific to the question at hand,
    Messier refers to the use of a "2-foot night-telescope" in the
    discovery of his 1773 comet. In the parlance of the day this was the
    name for an RFT telescope, one with a relatively large aperture, a
    short focal-length, and low magnification with a relatively wide FOV.

    There are several additional points regarding this subject worthly of
    note. Firstly, virtually all of Messier's discoveries were of comets
    verging on, or of, nakedeye visibility. Very little aperture would have
    been needed to render most of the obvious. Only one or two of his
    comets were clearly below 7th magnitude, while his "comet-like
    objects", particularly the galaxies, were often decidedly fainter.
    Important as well is the concept of Messier's catalog. For the most
    part is was supposed to contain objects that initially could have
    mistaken for comets during his searching. However, if viewed with even
    a modest-sized refractor of 75x-120x, all the Messier star clusters as
    obviously just what their name implies. Only when a very small
    aperture, low power telescope is employed do these objects in any way
    begin to resemble comets. Thus, the catalog was intended for use in
    comet hunting with a very small, low power instrument. Finally, the
    idea of serious comet hunting with an 18th century long-focus, very
    limited FOV, telescope, such as the majority of those contained in the
    preceding list, is just nonsense, as careful sweeping of a swath of sky
    even 30-degrees wide could not begin to keep up with the dirunal motion
    of the sky. Doing so with the typical weather of Paris would have
    doomed Messier's comet-hunting efforts!

    JBortle


  3. #13
    Sam Wormley's Avatar
    Sam Wormley Guest

    Default Equivalent scopes (or binocs) to match Messier telescope(s)

    CNJ999 wrote:

    Thanks John.

  4. #14
    CNJ999's Avatar
    CNJ999 Guest

    Default Equivalent scopes (or binocs) to match Messier telescope(s)

    To set the record straight once and for all and in hopes that perhaps
    this post, or at least the listing below, might be referenced in the
    future when the question of Messier's cometseeker(s) arises, I have
    gone back and once again examined what the historical record indicates
    re this question. Charles Messier is credited with 13 discoveries
    nowadays, although he spotted several additional comets somewhat
    belatedly. The listing below gives the year of each comet officially
    carrying his name, its probable magnitude at the time of discovery, and
    the instrument reported as used in the discovery, if any.

    1759II / 5-6 / 1-foot telescope
    1763 / 5-6 / 1-foot telescope
    1764 / 3 / nakedeye
    1766I / 6 / 6"f/5 Gregorian or 5-foot achromat (different
    sources give conflcting ID)
    1769 / 5-6 / "small telescope"
    1770I / - / no listing for instrument, could have been the
    nakedeye
    1771 / 4.5 / naked eye
    1773 / 5-6 / 2-foot "Night-Telescope"
    1780I / - / 3.5-foot achromat
    1785I / - / "small telescope"
    1788 / 5 / "Night-Telescope" (probably the old 2-footer)
    1793I / 5 / "small telescope"
    1798 / 6 / no listing for instrument

    During Messier's lifetime, Short, the Dollands, and others were
    producing some small, short focus, low power refractors in addition to
    their ungainly, long-focus, lenses and Gregorian telescopes. The
    concept of low-power, wide-field, telescopes for the singular purpose
    of comet hunting seems to already have formed among the successful
    comet hunters by the latter half of the 18th century.

    So, referring back to the poster's original question, today's
    equivalent to Messier's 2-foot Night-Telescope might be a 50mm to 70mm
    monocular of somewhat less than outstanding quality, magnifying between
    10 and 20 times (or perhaps a standard 50mm viewfinder?).

    JBortle


  5. #15
    Chris L Peterson's Avatar
    Chris L Peterson Guest

    Default Equivalent scopes (or binocs) to match Messier telescope(s)

    On 30 Nov 2005 16:36:22 -0800, "CNJ999" <jbortle@aol.com> wrote:


    Perhaps. I think, however, looking at the published list of
    magnifications and focal lengths for many of his telescopes, and looking
    in particular at his actual descriptions of the objects, that Messier
    was using quite a bit higher power. He may have utilized a low power
    telescope for his searching, but it seems very likely that he used more
    for his closer study. Many of his descriptions are simply inconsistent
    with what could be seen at 10-20x.

    _________________________________________________

    Chris L Peterson
    Cloudbait Observatory
    http://www.cloudbait.com

  6. #16
    CNJ999's Avatar
    CNJ999 Guest

    Default Equivalent scopes (or binocs) to match Messier telescope(s)


    Chris L Peterson wrote:
    The original poster asked if anyone could provide the modern equivalent
    in aperture and magnification of the instrument Messier used to
    discover his objects. The question was not what scopes were employed in
    follow-up positional or descriptive observations. I had pointed out in
    my both of my initial posts that these differed quite dramatically.

    JBortle


 

 
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