NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Sun activity
From: Richard B. Emerson
Date: 2001 Sep 06, 6:21 AM
From: Richard B. Emerson
Date: 2001 Sep 06, 6:21 AM
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