When less aperture is preferred

Dec 11

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12/11/2012 8:27 PM  RssIcon

Because of clouds or other commitments, I don't always get to view every single object I talk about in the "Eyes on the Sky" videos near the time I talk about them.  Usually I have seen these objects at some time in the past, though not always.  This week is a good example; I know what the larger asteroids in our solar system should look like - I just hadn't ever actually seen one before.

Until now.  Of course, it looked very star-like, unlike the high-resolution photo on the right.

I literally went outside with just my coat on (it got pretty cold here near Chicago early this week), did not bother to dark adapt, and simply had my 7x50 binoculars around my neck.  I had taken a good look at the star chart I made, and made a mental note of where the 5th and 6th magnitude stars near Aldebaran and Vesta were, and what they should look like in my binoculars.  Basically, I remembered a skewed trapezoid shape, knowing that Vesta should be only as bright as the dimmest star in that trapezoid, and it's location would be somewhere slightly below the lower two stars, but nearly centered.  It helped that also knew approximately how far to move my binocular field from Aldebaran to find my target area.

Knowing the field of view really does matter.

It took me less than 10 seconds, and sure enough, there it was - dim, but right where it should be.  Now, if I'd dark-adapted even a few minutes, or bothered to take out a slightly larger telescope, it would have looked brighter.  But in a way, this was a good thing: I knew that the other stars in the area would be far dimmer than Vesta - 8th, 9th magnitude or dimmer.  So because I was NOT dark adapted, those stars weren't even visible.  What was visible was exactly what I wanted to see: My four "trapezoid" stars, and Vesta.  That's it.  Nothing to muddle the view or confuse me.

And that is when using less aperture can be of benefit.  So often we're told, "Bigger is better," or "You always want more aperture."  

That's not always the case.  It was a "less is more" moment, and Vesta did not disappoint.  Sometimes it's a matter of, "What is the minimum aperture I need to get the job done."

Done.  Cut.  Print.

Or... something like that. ;-)

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The Nightlight

This blog includes what to see in the night and daytime skies, thoughts on telescopes, binoculars, and other astronomy observing accessories and equipment, plus my own occasional notes on objects I've seen and observed. Oh, and the random theater or other "my take on life" post. In other words, there is always something interesting. Check it out.