Friday, February 19, 2021

Junk Scopes: Meade Infinity 60mm & 70mm

In this article, I'm going to talk about two more junk scopes being sold under a major brand name. Though I am pointing out bad scopes in this post and the last, I want to be clear that there are good telescopes for beginners and youth on the market. I will be highlighting some of those in other articles. They cost a bit more. But they are worth it, because scopes sold for under $100 (U.S.) have to make compromises that ruin their ability to view the night sky. Even under $200-300, there are going to be compromises, but they aren't always going to be deadly ones that ruin the scope.
The scopes I brand as "Junk Scopes" are just junk. They don't just make compromises, they're basically unusable without a superhuman effort. They destroy an interest in science, rather than nurture it. The companies that sell them should be embarrassed to have their name on them.

Today, we're looking at two scopes on the dreaded "Yoke Mount." Back in the 1960s and 1970s, many small telescopes were sold with this terrible mount. Later, we saw improved designs for beginner scopes begin to displace this design, such as the small Dobsonian, fork mounts, and pan-tilt heads with workable slow motion controls. My first and second telescopes had terrible yoke mounts. I fought the mounts far more than I ever looked at anything in the sky with those telescopes. When I was a teenager, I modified them to make them somewhat usable, but they were never good mounts. Here's a closer look at the yoke mount on the Meade Infinity 60 and 70mm telescopes:

There are three fatal flaws to the yoke mount:
  • You can't lock it on the thing you're looking at.
  • You can't keep it on the thing you're looking at.
  • You can't move it smoothly.

  • Notice the silver bar that goes across from the mount to the tube of the telescope. That was a 1970s addition to try to make the yoke mount usable without actually fixing it. You can't balance a telescope that's screwed directly to its mount. Which means it's going to slip off its subject. The locking mechanism on a yoke mount (friction from a thumbscrew) isn't strong enough to hold a scope up that is the least bit unbalanced, so they put this locking bar on to try to give it more strength to hold the scope. Spoiler: It doesn't work.

    The scope will still slide off target, the bar will get scarred from the lockscrew making it rough and bumpy, making the movement of the scope in altitude (up and down) even worse than it already is.
    And it's already bad because of the trunnions (the "ears") that sit in the fork. They and the fork aren't shaped right for each other. It can sit there, but when you try to move it up and down the friction varies, meaning it has favorite places to rest and places it just won't stay put at. Which means you can't point your telescope at the thing you want to look at. Even something as big as the Moon. It won't do it.

    The central shaft under the fork, on top of the tripod, is part of why you can't use this scope. Notice that lock screw? When you try to use it, it will shift the entire scope by pressing against the support for the fork above. It will only move it a fraction of an inch. But that little move right there will throw the telescope off into an entirely different part of the sky. If you don't use the lock, the scope will move too easily, again, throwing it off into a completely different part of the sky. You lose either way.

    The upshot is, if you see a yoke mount on a telescope, run away!
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