Finder Scope For The Window Telescope

Posted by Bad Bob
on Sunday, February 14, 2010

       I took this photo shortly after completing (in a preliminary way) the finder scope for my window telescope. The finder's eyepiece is the large black entity above the main telescope tube in the right part of the photo. It is a homemade "Huygens" eyepiece (this eyepiece has an equivalent focal length of approximately 8 inches!) that I put together from sheets of black cardboard and glass magnifyers that I bought from a local dollar store (the field lens of this eyepiece has a diameter of 100 mm!) Notice that this eyepiece (you can see the eye lens of the eyepiece by the reflections off the glass surface) resides in a relatively convenient location, close (but not too close) to the eyepiece of the main 4.7-inch refractor. The objective lens of this finder is not visible in this photo; it lies just to the side of the 4.7-inch lens, intercepting starlight reflected from the 12-inch flat mirror, just as does the main refractor's 4.7-inch lens; the light from the finder objective is reflected upward by a small flat mirror to a second small flat mirror (visible in this photo; this mirror is mounted in a ring of light bluish-green plastic), which reflects the starlight into the finder's Huygens eyepiece. The finder objective is made from the lens in a pair of dollar store eyeglasses (f.l. approximately 32 inches) and the two mirrors come from two of my mother's old make-up compacts and, even though they are second-surface mirrors, they are only about 1 mm. thick and have amazingly good optical quality, probably good enough for this 4-power finder scope (I looked after my mother at home until she passed away in 2007 at the age of 96). I will send more photos and give updates on how well this telescope and finder actually work at observing the universe (the finder scope has an actual field of view approximately 8 degrees wide, which should allow me to conveniently sweep the southern sky by the flat mirror's control arms, the long, thin pieces of wood shown in the photo). I should also mention that the finder tube is held in place by two crudely-cut pieces of cardboard from a box I got for free from a grocery store. I was thinking about painting them eventually, but I will likely leave them as they are; in any of my telescope-making projects, I like to leave something humorous as part of the construction; many of my friends would likely state that my entire projects are humorous!                                           

Bad Bob

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