What I Learned Today
I'm just back from an install job. I ran into some unusual stuff and want to leave some record, in case someone else runs into the same.
So, this morning my job was to install a replacement computer, copy all the files over, and then install a couple of CAD/CAM programs--MasterCam 8 and MasterCam X3.
Now, this was a machine shop, with some older equipment; he was using serial port networking, for compatibility. We were installing a Windows XP machine (for backward compatibility). The only thing that was relatively new was the replacement computer.
Not that I don't understand. I'm a great one for holding onto something that still works, until it doesn't. These guys were early adopters of computerized milling; they have big bucks tied up in their investment; and so they need special, obsolete equipment to support it.
So, I turn on the machine, do a little setup, copy over the files. Good so far. Next, I installed Aladdin drivers (MasterCam uses a hardware hasp for registration), and then MasterCam 8. Ran it to confirm that all was good.
Now I installed MasterCam X3. Ran it to confirm that all was good.
Just for fun, I tried running MasterCam 8 again.
Wouldn't run. Couldn't find an ocx file.
I did a repair install. Ran it. Tried to open a file. Crash.
For the next couple of hours, I tried various permutations of the install order, while searching online, for answers, til I was blue in the face. Crash. Crash. Crash. You get the idea.
I took five, had a think out in the brilliant sunshine. Immediately after installing X3, 8 couldn't find an ocx file. Now, I knew that an ocx is so named because it is an "OLE Control Extension." I also knew that it had to be registered. What if, somehow, during the install process it had been unregistered?
On the machine, in Windows Command Prompt, I ran:
regsvr32 mcbitmap.ocx -u
then
regsvr32 mcbitmap.ocx
(The first iteration unregisters object, just in case. The second reinstalls it.)
And it still didn't work.
Ah, said I. Windows XP is old stuff, and quite frequently needs rebooting after system changes.
I rebooted, and we were off to the races.
Oh, and the serial port networking? It just worked.
*Phew!*
-Bill
Friday 22 February 2019
Wednesday 13 February 2019
"Is That a Star, or a Planet?"
Occasionally, you'll notice a passerby spotting a particularly bright star and asking, "Is that a star, or a planet?"
Here's how to tell the difference--and why there's a difference.
In real short form, the difference is that stars twinkle, while planets shine steadily.
Now, why is that?
The answer lies in the apparent diameter of a planetary disc, versus the apparent diameter of a 'turbulence cell' in the upper atmosphere.
Let's go back to the beginning. In any amateur telescope, a star is an infinitesimal point of light. You can magnify it to the limits imposed by the physical parameters of your telescope; but unless you're using a huge, research-grade instrument, you'll never get a measurable disc from a star. What you see in your telescope is a 'diffraction disk,' whose size is a direct measure of the perfection of your instrument; the smaller, the better.
A planet, however, being much smaller than any star, but also much, much, much nearer, displays a measurable disc. Some--Jupiter, Venus, Saturn, for example--show a measurable disc in binoculars. Some people with very sharp eyesight can actually see for themselves. The point is that a planetary disc is much larger than a star's.
Now we must shift our attention to the upper atmosphere, where cells of air are shifting up and down and otherwise roiling with motion. On most nights, the cells tend to be of on the order of a metre or two in diameter. From the ground, that makes their apparent diameter larger than a star's, but much smaller than a planet's.
So, a star--that point source of light--is affected by every turbulence cell between you and it, and it will twinkle in all but the most exceptionally stable sky. In a telescope, you'll find that it will even change apparent position minutely, from instant to instant, the result of refraction effects.
With a planet, it's very much different. The entire planetary disc is covered by dozens, even hundreds, of individual turbulence cells; their combined effect is negligible.
That's not to say that a particularly unstable sky won't still ruin planetary images. In 'bad seeing,' the planetary disc will appear 'smeared,' with lower definition, at times misshapen and shimmering, because of all those turbulence cells roiling away.
So now you know; and now you know why. Another Useless Fact for your exploitation. You're welcome again. ;-)
-Bill
Occasionally, you'll notice a passerby spotting a particularly bright star and asking, "Is that a star, or a planet?"
Here's how to tell the difference--and why there's a difference.
In real short form, the difference is that stars twinkle, while planets shine steadily.
Now, why is that?
The answer lies in the apparent diameter of a planetary disc, versus the apparent diameter of a 'turbulence cell' in the upper atmosphere.
Let's go back to the beginning. In any amateur telescope, a star is an infinitesimal point of light. You can magnify it to the limits imposed by the physical parameters of your telescope; but unless you're using a huge, research-grade instrument, you'll never get a measurable disc from a star. What you see in your telescope is a 'diffraction disk,' whose size is a direct measure of the perfection of your instrument; the smaller, the better.
A planet, however, being much smaller than any star, but also much, much, much nearer, displays a measurable disc. Some--Jupiter, Venus, Saturn, for example--show a measurable disc in binoculars. Some people with very sharp eyesight can actually see for themselves. The point is that a planetary disc is much larger than a star's.
Now we must shift our attention to the upper atmosphere, where cells of air are shifting up and down and otherwise roiling with motion. On most nights, the cells tend to be of on the order of a metre or two in diameter. From the ground, that makes their apparent diameter larger than a star's, but much smaller than a planet's.
So, a star--that point source of light--is affected by every turbulence cell between you and it, and it will twinkle in all but the most exceptionally stable sky. In a telescope, you'll find that it will even change apparent position minutely, from instant to instant, the result of refraction effects.
With a planet, it's very much different. The entire planetary disc is covered by dozens, even hundreds, of individual turbulence cells; their combined effect is negligible.
That's not to say that a particularly unstable sky won't still ruin planetary images. In 'bad seeing,' the planetary disc will appear 'smeared,' with lower definition, at times misshapen and shimmering, because of all those turbulence cells roiling away.
So now you know; and now you know why. Another Useless Fact for your exploitation. You're welcome again. ;-)
-Bill
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