Tuesday, July 25, 2006

It's a hard-knock life for us, it's a hard-knock life for us! --Annie

First off, the good news: I'm getting my grubby little paws on a friend's digital camera tomorrow. Prepare for some rather amateurish photos of flowers, trees, my garden, the marsh, and the bunny and the kitties!

Now—to the hard knocks.

It seems one can learn a lot by trial and error. In my case, mostly by error. I finally began corresponding with "astronomy boy" Jeff DeTray, and he cleared up some important little details for me regarding such things as focal length (FL), scope tube length, and optics. As a result, I'm having to rethink this whole scope project.

But don't despair! With just a few adjustments, a couple of purchases, and some tape and stuff, I should be on my way!

Let's go through the illusions shattered:

1. If I use my 26mm FL eyepiece and the 800mm FL objective lens, my scope will have be almost 32 inches long. Not exactly what I had in mind for a portable, user-friendly scope. Granted, the power would be 30X, but it's just not practical.

2. If I use the 26mm FL eyepiece with the 200mm FL objective, my scope will only have about 7X power. That's barely enough to read the spines of the books on my bookshelf from my couch. BUT the scope would only be about 8 inches long! Hey—bright side, people, bright side.

Jeff went on to tell me that spotting scopes work with short-FL eyepieces and objectives with FL of 350 to 500mm, hence, their shorter tube length as well.

Thus, my new plan:

1. Order a new eyepiece—there's a two-element RKE eyepiece set with a FL of 8mm. Back to the Surplus Shed web site. Only $3.50.

2. Pair the 8mm FL eyepiece with the 200mm FL objective lens, in a tube that will be about 8 inches long. (200mm = 7.87 inches) Portability with 25X magnification. Not too bad.

3. Buy a 45-degree image-erecting diagonal. I was going to just look at things upside-down and backwards, but when I made a low-power experimental prototype last night, I discovered it's much harder to use than I thought it would be. I figured I could just adjust my brain like you do when you're brushing your hair in the mirror, but it just makes it really hard to sight things through the scope. I have enough problems just by accident without inventing more of them for myself.

For the prism, I have a couple of options.

a. The semi-expensive option: I could buy a 45-degree diagonal from Orion for $40. It would be easy to mount on the end of the tube then just attach my eyepiece and I'm good to go.

b. The cheaper option: Buy a prism, make a mounting for it, and then attach it somehow to the tube. I'm tempted by my desire to keep things as low-priced as possible; however, will it end up being a big mess like the rest of this project has been? Should I just bite the bullet and spend the $40 and get the pre-mounted thing? Or should I retain my pioneer spirit, my can-do attitude, and buy the prism and make a mounting out of god-knows-what—puka shells? How would I know? What do I know about mounting prisms?

What to do, what to do. I suppose I should just buy the mounted diagonal. It would make putting the scope together easier.
. . . what would Galileo do?

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