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From: TerryMosel@aol.com
Date: Thu, 22 May 2003 19:01:29 EDT
Subject: Kingsland Obs; Annular Eclipse

Hi all,

1. Eamnon Ansbro's Kingsland Observatory in Co Roscommon will be shown on RTE 
1 Nationwide on Friday 23rd May at 7pm.

2. Partial / Annular Eclipse, 31 May.  The eclipse is partial throughout 
Ireland, with maximum eclipse ocurring before sunrise in all parts of the island, 
so that the magnitude of the eclipse is decreasing from the moment of sunrise 
onwards. The following figures for maximum eclipse at different spots may 
differ from other quoted figures, which relate to the moment of sunrise. But 
that's not much use, since at that time the whole of the sun's disc, apart from the 
extreme upper edge, is still below the horizon! These details are for the 
time when the WHOLE of the Sun's disc has risen: Fair Head 72% (at 04.58 BST); 
Larne 70%; Coleraine 68%; Bangor 67%; Belfast 65% (at 05.00); Derry 62%; 
Newcastle (Down) 60%; Armagh 58%; Newry 58%; Omagh 58%; Enniskillen 53%; Dublin 47% 
(04.10); Galway 26 (04.22)%, Limerick 26%; Cork 19% (at 05.26). You can 
interpolate the time of sunrise for intermediate points
  ANNULARITY:  Some of you may be going to N Scotland to observe the eclipse, 
which is annular over the extreme North of the Country, with best views from 
Orkney & Shetland. Even there, annularity occurs with the Sun only a few 
degrees above the horizon, so a clear view to the NE, and a totally clear sky, will 
be required.
   Since the Sun will be so low, will the normal safety precautions for solar 
observing be required? The safe answer is of course yes, and particularly so 
as it gets higher up during the later partial phases. But when it is within a 
few degrees of the horizon, normal visual grade solar filter ('Mylar', or 
Baader Astro-Solar), may be too dense to show the event clearly.
  So Photo-grade Mylar, which transmits 10 times more light than 
visual-grade, may be OK for visual observing, BUT ONLY WHEN THE SUN IS STILL LOW DOWN.
   And if you want to take photos of it very low down, the photo-grade mylar 
may give too faint an image. If you have ordinary photographic Neutral Density 
filters, try some of the densest of these (ND4 & ND5). 
   In fact, if you use a slow film, a long focal length, and a small 
aperture, particularly with a Barlow or tele-converter, you may not need filters at 
all. I'm sure we have all managed to take photos of the Sun at sunset without 
any special filters at all! But that was probably when it was dimmed by haze or 
some cloud, giving a nicely reddened and fainter image!
   What we will be hoping for is the clearest most transparent sky possible, 
so if we get that, the Sun will be brighter than usual for that altitude.
    So use common sense, and err on the side of safety, particularly for 
observing as opposed to photography (a camera is replaceable, your eyes aren't). 
And of course it particularly applies if you are using binoculars or a 
telescope.
    We may get some nice views of Baily's Beads at the thin edge of the 
'crescent' at the start and end of annularity, but of course there will be no view 
of the Corona, prominences, or the chromosphere.
Are many of you going to Scotland? I know of a few, plus a couple going to 
Iceland where the view is slightly better.

Good Luck,

Terry Moseley

Last Revised: 2003 May 23rd
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