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Subject: Sun activity
From: Richard B. Emerson (navsys@XXX.XXX)
Date: Thu Sep 06 2001 - 08:20:53 EDT
Herbert Prinz writes:
> Russell Sher wrote:
> > [...] I also heard on the local news that solar activity may affect satellite communications
> > between now and October 15 - one wonders whether this could affect GPS
> > signals.
>
> It is also likely to affect sextant navigation: While shooting the
> sun, the navigator might become entranced observing the sun spots
> and mess up the sight. Last week there were several so called
> "naked eye sunspots" to be seen. To be sure, "naked eye" refers to
> the size only and is not to be taken litterally. A sextant,
> however, is a suitable observation instrument.
While practicing on Monday while sailing up the Chesapeake, I did
notice the last of Active Region 9601 towards the west limb of the
Sun. AR 9591 was comparable in size; AR 9601 was just barely visible
in my 6x monocular so I think these groups were "close but not quite".
It's been a while since a really large sunspot grouping ("naked eye"
size) has formed but, particularly last summer, I have been able to
point out "naked eye" sunspots as the Sun set, dimming its light
significantly. It's a surprise when people think "that dot" isn't a
bird or cloud but a giant sunspot. For those interested in observing
the Sun safely, filters can be made with "Baader film", a safe and
optically clean film developed in Germany. Try Scope Stuff at
http://www.scopestuff.com and drill down to the Baader film page. An
A4 sized sheet (7.9" x 11.4") of film costs $29.99. Instructions for
making custom filters with little more than card stock from manila
folders and the film are included on the page. A good web site for
white light images of the Sun is
http-://sohowww.nascom.nasa.gov/sunspots/
and a good site for reports on overall space weather (e.g. risk to
satellites) is
http://www.sec.noaa.gov/SWN/
Rick
S/V One With The Wind, Baba 35
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