Tuesday, January 05, 2010

New Telescope

On the Carousel of Hobbies, the astronomy horsie has apparently come around again. I was big into it a few years ago, I built an 8" reflector that packed down into a suitcase, which I brought to Moab, Utah with us. Unfortunately it was much cooler in its transformer-like aspects than in actual optical performance. Then I owned a series of cheap commercial scopes. I enjoyed the 4" refractor the most.

Refractors are the ones that most people picture when they picture a telescope - glass at the front, eyepiece in the back, long tube in the middle. They have mostly been supplanted by reflectors, which use mirrors instead of glass, and can be built much larger. But there's some holdouts for the refractor, mostly because they can be sharper on planets and the moon.

I bought a small refractor (3 inches) from Craigslist and was hooked again, so I started looking for bigger ones, but they are either expensive or poor quality. I went over to SurplusShed.com and found that they had a 127mm mounted objective (the glass in the front) for about $150! Since 5 inch refractors from commercial sources start at $400, this was quite a deal, so I got the objective and a cheap focuser.

Since Mars is approaching us in January I wanted to be sure I had something to look at it with. The small refractor I have is too small to give much magnification, and I didn't want to go find the right diameter aluminium tube for the big lens, plus buying all the stuff to do it "right" would end up costing as much as buying the commercial one in the first place.

So.... here's what I have so far. A lens and a focuser on a plank, supported by plumbing fittings and a big ugly tripod. As simple as you can get. I am planning to enclose the tube with some lightweight paneling and add blackout paper to the inside, but this works! I'm really pleased with the performance of the lens, I was able to see the polar and equatorial belts on Jupiter just fine last night (before my butt froze off).

I took the focuser apart and re-greased it and shimmed it so it doesn't move around all over the place. Next step will be to check the collimation (alignment) of the lens and eyepiece, close in the tube, and paint it.

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