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From: freeman@spar.UUCP (Jay Freeman)
Newsgroups: net.astro
Subject: Re: Pleiades, Meteors, Comet Halley
Message-ID: <477@spar.UUCP>
Date: Wed, 21-Aug-85 17:19:11 EDT
Article-I.D.: spar.477
Posted: Wed Aug 21 17:19:11 1985
Date-Received: Sat, 24-Aug-85 18:54:52 EDT
References: <1428@cbosgd.UUCP>
Reply-To: freeman@max.UUCP (Jay Freeman)
Organization: Schlumberger Palo Alto Research, CA
Lines: 32

In article <1428@cbosgd.UUCP> djb@cbosgd.UUCP (David J. Bryant) writes:
>I've heard stories about reliable observers back in the 1700's who reported 
>seeing as many as 14 stars in the Pleiades.  ... I only see six, as do most
>people I've talked to. ... I've never viewed the nebulosity naked eye, nor
>have I heard anyone claim to.

I can maybe see eight stars naked-eye under excellent conditions.  I also
believe I can see nebulosity filling the cluster under similar conditions,
though there are a couple of necessary caveats:

(1) Bright stars seem to "spread out" on the retina in any case, so that one
must always suspect self-deception.  My conclusions are based in part on
differential observations of closely-spaced stars where there is no
nebulosity (in some cases rich-field telescopic views of clusters, for there
is certainly no northern-hemisphere cluster as bright and compact as the
Pleiades); in part on comparing the difference in appearance of the Pleiades
on the best of nights and on occasions when it isn't quite so dark.  To my
eyes the cluster looks distinctly nebulous on good nights.  The appearance
resembles what I see through 7X50 or 11X80 binoculars under similar
conditions -- the whole cluster immersed in a blob of nebulosity whose
diameter is perhaps twice the width of the group of six naked-eye stars.

(2) A trace of fog or high cloud will make bright stars appear nebulous.
Again the test is differential observations.

(3) It is easy to "see" something when you know it is there.

(4) I suspect that the brightest part of the Pleiades nebulosity -- the
Merope Nebula -- is too close to Merope to show well for the naked eye.
Thus it does not surprise me that what I see is a whole cluster full of
nebulosity, not just patches near the bright stars.
-- 
Jay Reynolds Freeman (Schlumberger Palo Alto Research)(canonical disclaimer)