So now the primary mirror is reflecting all the light back to the front of the tube. But if you look down the tube, you block all the light. This is where the secondary mirror comes in. This secondary mirror is a small flat fellow that sits inside the tube, and reflects the concentrated spot of light out the side of the tube.
Now at the side of the tube is the eyepiece and focus mechanism. All the magnification comes from the eyepiece. The magnification can be calculated as the ratio of the eyepiece focal length to the primary mirror focal length.
-4.5" F/8 36" focal length primary mirror with adjustable mount,
secondary mirror w/mount and spotting scope: $29.75 from the
-Reflector focuser assembly (really junky): $19.95 from the surplus shed.
-25 and 12.5 mm focal length PLOSSL eyepieces: $28.50 each from surplus shed.
-6" Nominal diameter PVC pipe, 5 ft long: $25.93 from McMaster-Carr
-6" Nominal diameter PVC pipe cap (lens cap): $9.75 from McMaster-Carr
-Monster BOGEN tripod: FREE from the nice dumper at Stanford
-Misc. hardware..nuts and bolts..
So this comes to a total cost of about $150 bucks. Not too bad
I'd say. I'll bet you couldn't touch one in the store for that
price and it was really fun to get working.
Here are a couple of photos; down the tube and a view of the spider (mount that holds the secondary mirror). And a couple shots of the moon...
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Last updated: 06/20/03