The Tube Straps

<body topmargin=0 leftmargin=0 marginheight=0 marginwidth=0> <table cellpadding=0 cellspacing=0 border=0><tr> <td valign="top" colspan=2 height=90 BGCOLOR="#006699" TEXT="#080000" bgproperties="fixed" background="015285a1erlcgo.gif"> <div> <FONT SIZE="3" COLOR="#FFCC66" FACE="Arial" ><B>N.T.L. - The Starfinders' Home          </B></FONT><A HREF="http://astronomie.n-t-l.de" TARGET="_top" TITLE="http://astronomie.n-t-l.de"><U><B>To NTL-AstroHome</B></U></A><B>     </B><A HREF="http://www.n-t-l.de" TARGET="_top" TITLE="http://www.n-t-l.de"><U><B>To  NTL-Homepage</B></U></A></div> <bR> <div> <A HREF="starfinder_types.htm" TARGET="_top" TITLE="Overwiew of Types"><U>Overwiew of Types</U></A>   |   <A HREF="starfinder_eq_eng.htm" TARGET="_top" TITLE="The Starfinder EQs"><U>The Starfinder EQs</U></A>   |   <A HREF="starfinder_faq_eng.htm" TARGET="_top" TITLE="The StarfinderFAQ"><U>The Starfinder-FAQ</U></A></div> <div> </div> </td> </tr><tr> <td valign="top" width=150 BGCOLOR="#FFCC66" TEXT="#080000" background="013d4c00dkelyh.gif"> <bR> <div> <B>Overview of Types</B></div> <bR> <div> <B><U>The Starfinder EQs</U></B></div> <bR> <div> <B><U>The SF1</U></B></div> <bR> <div> <B>The</B></div> <div> <B>RA-Drive</B></div> <bR> <div> <B>Astro Photography</B></div> <bR> <div> <B>Stabilizing the </B></div> <div> <B>tube straps</B><FONT SIZE="3" COLOR="#003399" FACE="Wingdings" >ü</FONT></div> <bR> <bR> <div> <B>The Dobsonians</B></div> <bR> <div> <B>The Starfinder-FAQ</B></div> <bR> <div> <A HREF="starfinder_eq_eng.htm" TARGET="_top" TITLE="The Starfinder EQs"><U><B>back</B></U></A></div> </td> <td valign="top" height=390 BGCOLOR="#000066" TEXT="#F7F7FF"> <bR> <div> <I><B>Stabilizing the tube straps</B></I></div> <bR> <bR> <div> The screws wich tighten the tube straps round the OTA are one principle flaw of the SF1 equatorial</div> <div> mount. Roughly spoken, they don't allow a stiff connection between the tube assembly and the mount's</div> <div> wedge. This is mainly because they are designed to be tightened manually.</div> <bR> <div> <IMG SRC="39700c00.jpg" border=0 width="256" height="192" ALIGN="BOTTOM" HSPACE="0" VSPACE="0">     <FONT SIZE="3" COLOR="#00FF00" FACE="Arial" >This is one of the two originial screws</FONT></div> <bR> <div> These screws have two disadvantages:</div> <bR> <div> <IMG BORDER="0" SRC="Symb075c00b700f000ccff00.gif" HEIGHT="16" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">On the one hand, it can be very painful to tighten these small screws with one's fingers, especially</div> <div> on cold winter nights.</div> <div> <IMG BORDER="0" SRC="Symb075c00b700f000ccff00.gif" HEIGHT="16" WIDTH="24" ALIGN="bottom" HSPACE="0" VSPACE="0">On the other hand one can't tighten these screws fast enough using only bare fingers.</div> <bR> <div> There is one very very cheap and simple workaround: a quarter inch nut!</div> <bR> <div> <IMG SRC="39900c00.jpg" border=0 width="256" height="192" ALIGN="BOTTOM" HSPACE="0" VSPACE="0">     <FONT SIZE="3" COLOR="#00FF00" FACE="Arial" >With this nut everything will be better!</FONT></div> <bR> <div> Using a normal wrench, You don't have to hurt Your fingers and You can fix the tube</div> <div> very tightly on the mount. You can improve the stability further on by putting some</div> <div> damper material (foam gum) between tube and wedge as shown in the next picture:</div> <bR> <bR> <bR> <div> <IMG SRC="39b00c00.jpg" border=0 width="256" height="192" ALIGN="BOTTOM" HSPACE="0" VSPACE="0">     <FONT SIZE="3" COLOR="#00FF00" FACE="Arial" >The OTA with additional damper element</FONT></div> <bR> <div> Of course I tried to measure the time needed by the OTA to stabilize after elongation.</div> <div> The scope was elongated at 44x magnification by a tough fingertip for about 1/4 degree in</div> <div> RA-axis-direction and in DEC-axis-direction.</div> <div> At 228x magnification the scope was elongated for about 0,2 degrees, the maximum sensful</div> <div> amount, which correlates to very hard touching the focusser. Elongation in this case was</div> <div> introduced via the focussing wheels.</div> <div> The decay times have been measured with a stop watch at the eyepiece without touching</div> <div> the tube. If You would damp the OTA a bit with Your fingers, You could reduce all these</div> <div> times about 50%.</div> <bR> <div> <TABLE BORDER="2" CELLPADDING="2" CELLSPACING="1" WIDTH="617" BORDERCOLORLIGHT="#C0C0C0" BORDERCOLORDARK="#808080" FRAME="BOX" RULES="ALL" ALIGN="BOTTOM" HSPACE="0" VSPACE="0" > <tR> <tD VALIGN=TOP BGCOLOR=#BBBBBB HEIGHT= 57 WIDTH="146"><div> <B>Setup</B></div> </tD> <tD VALIGN=TOP BGCOLOR=#BBBBBB WIDTH="146"><div> decay time/ amplitude @  44x in </div> <div> RA-axis</div> </tD> <tD VALIGN=TOP BGCOLOR=#BBBBBB WIDTH="146"><div> decay time/ amplitude @ 44x in DEC-axis</div> </tD> <tD VALIGN=TOP BGCOLOR=#BBBBBB WIDTH="146"><div> decay time/ amplitude after focussing @ 228x</div> </tD> </tR> <tR> <tD VALIGN=TOP HEIGHT= 19 ><NOBR><div> MEADE screws</div> </NOBR></tD> <tD VALIGN=TOP WIDTH="146"><div> 5,5sec / 0,25°</div> </tD> <tD VALIGN=TOP WIDTH="146"><div> 4,0sec / 0,25°</div> </tD> <tD VALIGN=TOP WIDTH="146"><div> 6,5sec / 0,2°</div> </tD> </tR> <tR> <tD VALIGN=TOP HEIGHT= 38 WIDTH="146"><div> MEADE screws + damper element</div> </tD> <tD VALIGN=TOP WIDTH="146"><div> 4,5sec / 0,25°</div> </tD> <tD VALIGN=TOP WIDTH="146"><div> 3,0sec / 0,25°</div> </tD> <tD VALIGN=TOP WIDTH="146"><div> 6,0 sec / 0,2°</div> </tD> </tR> <tR> <tD VALIGN=TOP HEIGHT= 19 WIDTH="146"><div> Standard nuts</div> </tD> <tD VALIGN=TOP WIDTH="146"><div> 4,5 sec / 0,25°</div> </tD> <tD VALIGN=TOP WIDTH="146"><div> 2,0sec / 0,25°</div> </tD> <tD VALIGN=TOP WIDTH="146"><div> 5,0sec / 0,2°</div> </tD> </tR> <tR> <tD VALIGN=TOP HEIGHT= 38 WIDTH="146"><div> Standard nuts + damper element</div> </tD> <tD VALIGN=TOP WIDTH="146"><div> 4,0sec / 0,25°</div> </tD> <tD VALIGN=TOP WIDTH="146"><div> 1,0sec / 0,25°</div> </tD> <tD VALIGN=TOP WIDTH="146"><div> 4,0sec / 0,2°</div> </tD> </tR> </TABLE></div> <bR> </td> </tr></table></body>