Eyepieces and Barlows

Guest · Posted: Wed Nov 21, 2007 12:46 pm Post subject: Eyepieces and Barlows

Is there any optimization of some types of eyepieces and barlows for particular types of telescopes e.g. refractor vrs SCT vrs Mak vrs Newton? I saw an ad for a barlow that said optimized for a SCT. I will be buying a refractor and I will need eyepieces and a barlow. I also saw one ad that said the barlow was specially designed for fast telescopes and this concerned me as I want a slower refractor. Getting confused. I thought I only needed to worry only about price and magnification but now I am wondering if design specificity is also critical. [I am only talking about 1 1/4" EPs and barlows].

Guest · Posted: Wed Nov 21, 2007 12:51 pm Post subject:

Can I ask the same question about diagonals. Are they interchangeable with various types of telescopes or are they type-of-scope specific?

Jne_K · Site Admin Joined: 24 Sep 2003 Posts: 5512

Hi

Eyepieces are interchangeable based on barrel size. For instance, any eyepiece with a 1.25" barrel size will fit in any focuser that uses 1.25" eyepieces. Any 2" eyepiece will fit in any focuser that uses 2" eyepieces. There is no need to specify an eyepiece based on telescope design, such as a refractor, reflector and so on. However, you need to select the focal length of the eypiece, carefully, to get the appropriate magnification for you application. A given focal length of eyepiece can produce a tremendous range of magnifications based on the telescope you use it in. To determine the magnification with any eyepiece and telescope combination, divide focal length of the telescope by focal length of the eyepiece.

Digonals are interchangeable, but not to the same extent. You need to consider the telescope design and, sometimes, the specific model of telescope in question. Proceed with caution, here.

For the basics and how to choose a telescope, see my article
How to choose the right telescope

For the basics on how to setup and use any brand of telescope, see my article, Telescope FAQs
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Guest · Posted: Wed Nov 21, 2007 3:45 pm Post subject:

Are you lumping barlows with EPs? So any barlow will work with any telescope (given there is enough focuser travel distance)?

Jne_K · Site Admin Joined: 24 Sep 2003 Posts: 5512

Hi

Yes, you can think of barlows as eyepieces as far as interchangeability, but you need to use this accessory, carefully. It is easy to produce more magnification than the telescope can handle with a barlow.
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