Safe solar observing

<body topmargin=0 leftmargin=0 marginheight=0 marginwidth=0> <table cellpadding=0 cellspacing=0 border=0><tr> <td valign="top" colspan=2 height=22 BGCOLOR="#330099" TEXT="#080000" bgproperties="fixed" background="040000d2erkqrf.gif"> <div> Derby and District Astronomical Society - Aries Magazine</div> <div> </div> </td> </tr><tr> <td valign="top" width=145 BGCOLOR="#333399" TEXT="#080000" background="03fa2c00erkjzj.gif"> <div> <A HREF="index.htm" TARGET="_top" TITLE="Aries Astronomy magazine on line From th"><U>HOME</U></A></div> <bR> <div> <A HREF="id52.htm" TARGET="_top" TITLE="Autumn 2001"><U>Autumn 2001</U></A></div> <div> <B>Safe solar observing</B></div> <div> <A HREF="id57.htm" TARGET="_top" TITLE="Venus"><U>Venus</U></A></div> <div> <A HREF="id56.htm" TARGET="_top" TITLE="TV listings"><U>TV listings</U></A></div> <div> <A HREF="sky_notes37.htm" TARGET="_top" TITLE="Sky scene November 2001 to February 2002"><U>Sky scene November 2001 to February 2002</U></A></div> <bR> </td> <td valign="top" height=458 BGCOLOR="#FFFFFF" TEXT="#080000" background="06a92963.gif"> <div> <B>Aries Astronomy magazine on line- From the Derby and District Astronomical Society</B></div> <div> <IMG SRC="04107040.gif" border=0 width="263" height="4" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <DIV ALIGN="LEFT"></DIV> <div>  <A NAME="askjeeves"><IMG BORDER="0" SRC="1x1.gif" HEIGHT="1" ALIGN="bottom" WIDTH="1" HSPACE="0" VSPACE="0" ></A><FONT SIZE="4" COLOR="#FF6666" FACE="Comic Sans MS" >Why not search the internet for more information about the Sun ...</FONT></div> <div>  <IMG SRC="http://service.bfast.com/bfast/serve?bfmid=31103363&siteid=35044309&bfpage=football" BORDER="0" WIDTH="1" HEIGHT="1" NOSAVE > <FORM ACTION="http://service.bfast.com/bfast/click" > <INPUT TYPE="hidden" NAME="siteid" VALUE="35044309" > <INPUT TYPE="hidden" NAME="bfpage" VALUE="football"> <INPUT TYPE="hidden" NAME="bfmid" VALUE="31103363" > <TABLE CELLPADDING="0" CELLSPACING="0" BORDER="0"> <TR> <TD 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</div> </NOBR></tD> </tR> <tR> <tD VALIGN=TOP HEIGHT= 34 WIDTH="466"><div> <I><B>Author: Maurice Batchelor</B></I></div> </tD> </tR> </TABLE></div> <bR> <div>  Just to recap on my previous article, Small telescopes intended for terrestrial use are often available at a relatively low cost but have limitations as far as astronomy is concerned. Terrestrial telescopes have extra lenses known as erecting lenses, which sets the image the correct way up. When light passes through a lens system, a small amount is lost (by reflection and absorption). This means that faint objects will not be seen as easily as with an astronomical telescope. There is, however, one particularly good use to which this type can be put – solar observation. </div> <bR> <div> (IMPORTANT SAFETY NOTE – do not look at the Sun directly through any optical instrument, it will blind you, projection is the safe method to use). <FONT SIZE="4" COLOR="#0099FF" FACE="Arial" > </FONT></div> <bR> <div> It is easier if the telescope is fixed to a tripod of some sort. With a little ingenuity, a suitable device can be fashioned if you don’t have one. The telescope should be arranged at a convenient height (see fig. 1). </div> <bR> <div> <IMG SRC="1567e2e0.gif" border=0 width="638" height="302" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <div> A piece of card can be supported on a nearby chair. This will act as a screen onto which the image of the Sun will be projected. A circle drawn on the card, corresponding with size of the image, is used to enable the sunspots to be marked in with a pen or pencil. This seems primitive but it is easy to set up and reasonably accurate if care is taken. Sunspots usually occur in fairly large numbers about every 11 years and the flares associated with them are responsible for good displays of the Aurora Borealis. Various theories exist as to what sunspots are and how they are formed. Incidentally, it was Galileo who first examined these through his newly made telescope in 1610. Basically, sunspots are rather like cyclonic storms, powered by the Suns strong magnetic fields, in which the expanding gases result in a drop in temperature. They appear dark because they are only half as hot as the rest of the surface. </div> <div> The Sun is our closest star, it is average to small in comparison with stars as a whole and vital to the existence of life on Earth. It is 864,000 miles in diameter and about 93 million miles distant. The light from it (travelling at 186,000 miles per second) takes about eight and one half minutes to reach the Earth (If you could drive to the Sun, at a steady 70 mph it would take 151 years, 8 months, assuming no toilet or food stops were made! - Ed). It takes 26 days for the Sun to rotate on its axis and it is noticeable how the largest spots travel across the surface, only to reappear 13 days later. The largest sunspot group recorded so far appeared in 1947 and covered an area of 7000 million square miles. About 100 bodies the size of the Earth could be fitted into this area! It was considered at the time to be an important factor concerning the weather, coinciding as it did with one of the most severe winters recorded in the twentieth century, as I well remember. As the sunspots travel towards the edge of the Sun’s disc, as seen from Earth, they appear to be foreshortened. This is known as the ‘Wilson effect’ after an eminent Glaswegian astronomer. </div> <div> So, to sum up the information from my two articles, the interested amateur needs only to be equipped with a pair of binoculars or a terrestrial telescope in order to begin to explore the skies with optical assistance. Even a modest pair of 8x40 binoculars will enable the user to view many more stars than are visible to the naked eye, whilst a terrestrial telescope will enable him or her to make records of sunspots (by projection of course). To graduate from this, when finances and space allow, a 3” (75 mm) refractor, or 6” (150 mm) Newtonian reflector are ideal. These have sufficient magnification and resolving power to show the belts and zones of Jupiter and the rings of Saturn. Below are some of the drawings that I have made using this simple set up.</div> <bR> <div> <IMG SRC="15fff720.gif" border=0 width="255" height="370" ALIGN="BOTTOM" HSPACE="0" VSPACE="0">  <IMG SRC="16154720.gif" border=0 width="340" height="370" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> </td> </tr></table></body>