2x or 3x barlow lens?

Question

I have the option of getting either a 2x or 3x barlow lens, and I have currently have one 25mm eyepeice, and I am expecting a 9 mm eyepiece later this week. Should I go with the 2x or 3x. I am beginning to think that the three would be too much magnification on my 9mm eyepiece, and too little magnification for my 25 mm eyepiece. Currently with my 25 mm eyepiece I am only getting 22x magnification, so I really need this barlow lens.

And also, is there a difference between using a barlow lens, and using an eyepiece that would get you the same magnification? Which is better. Thanks

Answer 1

what kind of scope? this is kinda important...

a barlow ups the magnification while maintaining eye relief, much more than an eyepiece with the equivalent focal length.

Answer 2

With a 25 mm eyepiece and a 9 mm eyepiece, the 2X is the better choice.  That way your 25 mm will act like a 12.5 mm and your 9 mm will act like a 4.5 mm.  That will give you four distinct magnifications.

With th 3X, your 25 mm will act like an 8.33 mm (too close to the 9 mm), and your 9 mm will act like a 3 mm.  You would really have only three distinct magnifications.

Optically, 2X Barlows are typically better than 3X.  

Long focal length eyepieces usually have better eye relief than short focal length eyepieces.  So if you use your 25 mm eyepiece with a Barlow, you'll have the same eye relief even with the Barlow in place.

The main disadvantage to a Barlow is that you'll probably have to move your focuser quite a bit when you insert the Barlow.  The shorter focal length eyepiece usually doesn't require as much focuser travel.

Personally, I like having the individual eyepieces and not messing with a Barlow.

Answer 3

3 * 9 = 27, which is much like 25.  I'd go with 2x, since it's more magnification options.

But i actually only use my 2x barlow with my high power eyepiece.  So maybe it matters more what high end magnification you want.

And, despite barlows being cheap magnification, my 10mm with 2x barlow does much better than my 5.1mm does without.  It's not the scope.  And it's not the eyepiece.  It's some combination of my eye and this particular 5.1mm eyepiece.  Other people like my 5.1mm just fine and on several scopes.

My advice, try before you buy.  Your club can help you there.  Don't have a club?  Why not?

Oh, it would have been nice if you told us your aperture and scope focal length.  Then we could have told you if the 3x barlow was just plain silly or not.

Answer 4

For the same magnification, using a Barlow means that you have the eye-relief of a longer focal length eyepiece - that's usually more comfortable, and important if you have to observe while wearing glasses. Adding more lenses is likely to degrade the image though.

The 3x Barlow is pretty pointless - in effect you'd end up with 8mm and 3mm eyepieces.  The 8mm is too close to the 9mm, and the 3mm would be almost useless.

Answer 5

i think i'd go with the 3x because it should be ok with your 25mm piece, and the 2x would be still way too much for your 9mm unless you are looking at something very bright.

Answer 6

Barlow lenses are cheap substitutes for doubling the magnification or 3times .But quality sufferes.

Answer 7

there is so much light loss from a Barlow that you are likely to use it once, store it and never get it out again.

Answer 8

A 2x barlow will double the magnification but reduce the light level by

one half. if your prime aperture is large enough,good results can be had.

the 3x barlow will triple the mag/reduce intensity by 3. etc