Friday, October 12, 2012

Stellarium and the Barlow Lens

In Stargazing on a cloudy night I wrote about configuring Stellarium's Oculars plugin so that Stellarium can show you what you'll see through your very own telescope. With the Oculars plugin you describe your telescope as well as your eyepieces.

What about the Barlow lens?  Essentially, a Barlow lens is a device which increases the focal length of your telescope, thereby increasing the magnification of the image in the eyepiece. In other words, an eyepiece which gives you 50x without a Barlow will give you 100x with a 2x Barlow.

I have a 3x Barlow lens to go along with my scope: the Orion SkyScanner 100mm.  Its focal length is 400mm, so when using the 3x Barlow with an eyepiece, it's as if my focal length is 1200mm. To use Stellarium's Oculars plugin with this particular setup, I just added a second telescope with the same parameters as the original telescope, but with the longer focal length. So in my case, I now have two telescopes, the SkyScanner 100, and the SkyScanner w 3x. 

I went out on the evening of October 11, and drew a sketch of Albireo, using the Barlow with a 10mm eyepiece:

Here's a screenshot from Stellarium with the same setup:

It's pretty cool how Stellarium can show you what you'll see when looking through your own scope.  

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