Re: [ATM] Odd question...

[Bern Kosicki <kosicki@verizon.net>]

At 06:34 PM 2/21/2008, Norm Prince wrote:
>Does pointing your scope at the sun w/o a filter cause any actual damage 
>to the mirrors/lenses of the scope?
>
>Obviously any attemt at observing would be harmful to a person w/o 
>filtration?...but does it hurt the optics???


You can use an unfiltered telescope or binoculars to project the image of 
the Sun onto a card to see Sunspots and other features.

I've done this for my Project Astro classes, and the kids love it to look 
at the images. (Right now of course the Sun if very quiet, but in a few 
years it should be showing a lot of Sunspots).

I use a standard 8 x 40 set of binoculars, with one lens blocked.  I've 
never had any damage to the prisms or optics that I've noticed.  Somewhere 
I read that about 40mm binoculars is the limit (don't try this with your 
large aperture astronomical binoculars, or the heat might soften the cement 
holding the prisims).  There is plenty of brightness to the image using 8 x 
40.

To see the image, you need to put some sort of shield around the 
binoculars- I use a piece of cardboard about 1 square foot in size, with a 
small hole in the center thru which I put the objective.  This hole needs 
to be a relatively tight fit- you want to cast a shadow into which you'll 
put the card to image the Sun.

You probably could also try this safely with a refractor (without using the 
diagonal).  The concentration of heat in the objective would not be an 
issue- but you wouldn't want to put your hand at the focus obviously.


Bernie Kosicki 

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