Hello Friend,

         Dobsonian Telescope set on fire by Sun...

         Yup, it's true.

Several years ago, while I was attending the annual STARFEST star party in Mount Forest, Ontario,
I was standing on the 2nd floor of the what was then the commercial vendors display building, on the
outside deck, and noticed that smoke appeared to be coming from an unattended large Dobsonian telescope.

     The owner had left it uncovered, and unattended and thus the Sun had crossed the path of the telescope,
and the intense reflected heat, set the instrument on fire. 

By the time I figured out what was happening, some quick thinking passers by who also noticed the smoke emitting
from the tube. ,  moved the instrument from the Optical
path of the Sun.  (Usually one hesitates to touch anyone else's equipment, but in this case, it was certainly warranted).

     So, keep this in mind, if you ever leave your telescope outside and unattended on a Sunny day.

There a few different methods of safely observing the Sun.

1) Solar filter that fits directly over the objective (front) of your telescope, these will show only Sunspots.

2) Dedicated Solar Observing telescope such as those made by Coronado or Lunt Solar Systems.
    These will show Hydrogen Alpha, and other surface detail on the Sun, and are 100% safe

3) Herschel Wedge: Baader makes a quality one. This is one of my personal favorites, because
   it works on most makes and brands of telescopes.

Some don'ts:

1) Projection method of the Sun against a wall or white background. 
    I hesitate to recommend this method, because the intense heat can damage cemented objective lenses.
2)Any kind of thread in solar filter that fits into an eyepiece (common with many telescopes manufactured several
    years ago. Throw these away! They can crack.

Clear Skies,

Ray "Sun of a gun" Khan

PS Always play it safe, when observing the Sun.  Don't use makeshift stuff, like Space Blankets, or untested types
     of Mylar. Stick with reputable brands and qualities.