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(IAAC) Re: Pothier naked-eye objects



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Lew Gramer <owner-netastrocatalog@jovian.com>
------- Forwarded Message
Date: Sat, 1 Jan 2000 13:44:13 -0700 (MST)
From: Brian Skiff <bas@lowell.edu>
To: WebbSoc@listbot.com
Subject: Re: Pothier naked-eye objects
The Webb Society - http://www.webbsociety.freeserve.co.uk
     Several weeks ago Yann Pothier posted a list of presumed naked-eye
objects visible from northern latitudes.  This is something I've thought about,
too, and having ready access to true-dark sky I have spent several years making
observations to test various candidates.  I append below Yann's list (with all
but the names trimmed out), with added comments.  Several objects in Yann's
list are shown twice under different names, and many of the Collinder clusters
simply are not real or much too sparse to be considered "deep-sky objects". 
Some objects are simply too faint, and published total magnitudes for some
clusters include a single bright star or two, but one would not see these as
clusters visually.
     Following from discussions elsewhere, I have posted an all-sky list of 
certain or near-certain naked-eye objects at the Lowell ftp area:
ftp://ftp.lowell.edu/pub/bas/deepsky/naked.dso
...to which I may add a few new ones based on Yann's suggestions.
     Although many of the objects are easy or straightforward from a true-dark
site, in the marginal cases one must be very careful to sort out neigbouring
mag. 7 and 8 stars in order to make sure you've found the correct object.  It
makes one's claim more useful if such details are provided as well.  I can post
a discussion of what was necessary to identify M81, for example, if desired.
     I was pleased to see that Yann included Sharpless 264 (Sh2-264), the
very large nebula surrounding the lambda Orionis group.  I find this readily
visible from the Lowell Anderson Mesa site, but I don't think anyone's ever
mentioned it in print being a naked-eye object.  On the other hand I have
never convinced myself that I could see Barnard's Loop because there are so
many faint stars strung along it that can mimic nebulosity.  Still again, the
Rosette Nebula is pretty easy to see even from a somewhat light-polluted
site when using a UHC or [OIII] filter.  This is a good target to start your
challenging naked-eye viewing with, since the change in the size of the object
going from unfiltered to filtered is dramatic.
\Brian
==================================
Blanco 1  too sparse
Cr 065    not real
Cr 069    lambda Ori cluster, easy
Cr 070    Belt of Orion, easy
Cr 089    not real
Cr 106    not real
Cr 121    too sparse
Cr 132    too sparse
Cr 135    too sparse
Cr 140    too sparse
Cr 316    = Trumpler 24 (preferred name)
Cr 399    easy; Brocchi's cluster = Coathanger
Cr 464    not real
IC 0348   too faint
IC 1396   nebula readily visible
IC 1805   nebula too faint
IC 1848   nebula too faint
IC 4665   straightforward
IC 4725   = M25; easy
IC 4756   readily visible
IC 4996   too faint, too small
M002      probably visible
M003      straightforward
M004      easy
M005      straightforward
M006      easy
M007      easy
M008      easy
M011      easy
M012      probably visible
M013      easy
M015      straightforward
M016      straightforward
M017      straightforward
M018      too faint
M020      easy
M021      straightforward
M022      easy
M023      easy
M024      = IC 4715; easy
M025      = IC 4725 above
M028      background too bright?
M029      too small/faint
M031      easy
M033      straightforward
M034      easy
M035      easy
M036      straightforward
M037      straightforward
M038      straightforward
M039      straightforward
M041      easy
M042      easy
M044      easy
M045      Pleaides
M046      straightforward
M047      straightforward
M048      straightforward
M050      straightforward
M052      maybe too faint
M062      background too bright?
M067      straightforward
M081      tough but visible
M092      faint
M093      straightforward
Mel 020   = alpha Persei cluster
Mel 022   = Pleiades
Mel 111   = Coma Berenices cluster
NGC 0253  reportedly visible from the south
NGC 0281  too faint
NGC 0752  easy
NGC 0869  easy
NGC 0884  easy
NGC 1499  visible with filter
NGC 1746  straightforward
NGC 1981  straightforward
NGC 2232  brightest star only
NGC 2237  Rosette Nebula, visible with filter
NGC 2244  Rosette cluster, easy
NGC 2264  brightest star only
NGC 2451  easy
NGC 2546  easy
NGC 5128  reportedly visible from south
NGC 6124  straightforward
NGC 6231  easy
NGC 6530  = M 8
NGC 6633  easy
NGC 6871  too small/faint
NGC 7000  North America Nebula; straightforward
NGC 7243  background too bright?
NGC 7293  several reports (without filters!)
Sh2-264   lambda Ori nebula, straightforward (much easier than Barnard's Loop!)
Sh2-276   Barnard's Loop; often confused with encircling mag 5-7 stars
Steph 01  delta Lyr cluster; brightest star only
Stock 02  bright background, barely discernable
Tr 10     probably visible, but in very crowded area
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