In writing when someone talk about an amateur writer, it’s often a pejorative term. In the astronomy world, that’s not the case at all. The word amateur comes from the word “amore” to love. So amateur astronomers are people who love astronomy. That’s a distinction between the writing world and the astronomy world that he loves.
It’s something you can get into as deeply or as lightly as you want. Essentially it involves looking at the night sky. Looking and learning what’s out there. Most of what he shared about the solar system, came from looking through telescopes and binoculars and being interested enough to learn more about it.
He’ll talk about the things you can do with simple things. Even without telescopes or binoculars.
Two basic ways to focus light and make an image. The point of a telescope is not to make an image bigger, but to gather more light.
Lenses – Refracting telescopes. The lightwaves cross over each other, so you put another lens in to flip it back over. The effect is to take all that light and fit it into a small enough beam to fit into the pupil of your eye. When you do that, you magnify the image.
Reflector – Light bounces off a mirror onto a secondary mirror and to an eyepiece.
With lenses you get a chromatic diffraction. When it goes through, the blue light gets focused in a different place than the red light. You can correct for that, but you have to do that with each wavelength you want to do that for. Each one must be ground to an incredible degree of accuracy.
With a mirror all the light hits the point you want it to. So you can get a much bigger surface for the money.
Most amateurs are reflectors. It’s so simple, you can grind your mirror. It’s easy, but time-consuming. A machine ground mirror used to not be good enough, but they are now. It’s still a rite of passage for amateurs.
Last stages of grinding are with pitch and jeweler’s rouge. The curve is very slight. 1/8″ over the surface of the glass. You aren’t taking off much glass. You push 200,000 times. You don’t want to make it spherical. You want to make it parabolic. The last stage is to have the back aluminized.
Binoculars will give you a very good view. Typical is 7 x 35. You pupil is only 7 millimeters, so a 35 millimeter objective is going to open up a lot of what you can see. The basic idea is that any tool you can use that will bring a lot of light down to a small point will help with seeing the stars.
There’s a phenomenon called “aperture fever” where you want to get bigger and bigger telescopes.
This is where the machine ground mirrors make a difference. When you’re pushing a piece of glass over another piece of glass about 2′ is about as big as you can reach. There’s pitch and it’s sticky. So machine ground amateur telescopes are starting to be available in the 36″ range.
The ratio of the diameter of the mirror and the actual focal point. The longer the focal length the more magnification. The downside is that the larger the magnification, the smaller the field of view.
The shorter scope gives you less magnification, but a larger field of view. You can vary the length of your eyepiece.
You can get about 50 power per inch of appateur. That would give you 150 power. Which is frankly more than most astronomers use, because you can’t see a very wide field. Most amateurs use 25 -30 power. Maybe up to 40.
Dobsonian telescope is mounted like a cannon. So it goes left right and top bottom. But the stars move in an arc, so you can’t follow them.
Equatorial mounts. The axis points at the north star. So you get the rotation, but it’s hard to set up.
Jerry has invented a new type of mount. Trackball. A ball that sits in a cradle.
Computer mounted scope with GPS. You point it north, then it swings to a bright star. It’s a little off, so you center it and tell it, “Yeah, that’s where Vega is.” Then it swings to another one. Again you center it. That locks it in. And from there you can tell the computer what stars it wants to see. The downside is that if you bump the tripod, then it has to be retrained about where it is.
Jerry says that he’s old school. The Harlan Ellison of astronomy, whacking away on his manual typewriter. He showed us a Star chart. Very cool. It’s like a puzzle. It’s a way to test your abilities and is fun.
The actual cost:
You can get a telescope, a really decent one, for $150, $200 which would give you a 6″ reflector. You can see a lot of stuff. For $500, you can get something with a motor which will track the star. An object will only stay in the eye piece for a couple of minutes. The sky moves 15 degrees per hour.
At star parties, you’re showing the public what you can see through the telescope, so you’ve got a long line of people waiting to look through the eyepiece. If your scope tracks then you don’t have to jump in after every person to reset the telescope.
They have a small refractor that they keep in the trunk of their car. So they can jump out and be viewing in minutes. It has a small finder scope, which is lower magnification, making it easier to aim it at the right part of the sky.
When doing photos, exposures are 5 to 10 minutes. So you have to guide it to nudge the star back to the center, or it will leave a streak. They call it the “world’s most boring video game.”
Schmidt-Cassegrain telescope is a reflector, but you look through the back.
Think about how much morning you’d spend on a boat. It’d be really hard to spend that much on amateur astronomy.
Truss-tube Dobsonian. There’s no tube, just an open framework.
Trackball telescope! Jerry invented this. It avoids the problems of the other two telescope mounts.
He showed us a bunch of photographs of telescopes which were very, very cool.
The deeper you get into the hobby, the more you want to make your own gear. A group of amateur astronomers stand around and talk and argue about gear. The motorized telescopes versus push telescopes. So it’s “Go-to” versus “push-to.”
6th magnitude star is the dimmest you can see on average with the naked eye on a dark sky. People can see 7th magnitude but 6th is average.
When you are looking at the moon, the best place to look is lunar sunrise or sunset, the terminator, because you get sharp shadows which make it easier to see the images.
Amateurs can do real science. “Real” astronomers love it when the amateurs do things like this. So, using different observers, at different latitudes, with synchronized watches, they can watch an asteroid occult a star. By doing this and carefully timing when it blocks the star and the star reappear, they can tell how the asteroid is shaped.
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One of the things that I found interesting is that a lot of the things that the telescope mounts are trying to solve are very similar to problems that puppeteers try to solve with neck joints and controls.
