eyepieces

Hey guys,
Shazzie again.I am a newbie to all this so this may sound like a stupid question :oops: but I have seen some of you talking about 3xBarlow lens-what exactly do these do,how much do they cost and where do you get them?Just wondering would they be a useful addition to th eyepieces supplied with the ETX-70 or can ye sucggest other eyepieces that might be needed.
Thanks again
Shazzie

Hi Shazzie,

If you bought your ETX70 in Lidl, then you should already have a 3x Barlow lens as one came with it, or at least, there was one in mine.
I'm new to this too, at least with a telescope. I've been at this about a year but have been using binoculars up till now. I don't know how good or bad the supplied 3x barlow is as I have, a) nothing to compare it to, and b) I haven't used it yet anyway! as for what it does, it does exactly what it says on the tin - it magnifies your view by 3. for obvious reasons, I can't/won't recommend anything, but am interested in what the more knowledgeable and esteemed members have to say.

Best of luck.

That will tell you how new I am I couldnt see any mention of a barlow lens just the magnification of the three eyepieces ie 25mm etc :oops: oh well I'll learn!

You should have the 3x barlow in the box from lidl. It is in a small Meade labelled box, and looks a bit like another eyepiece.

Slot an eyepiece into this and then slot the whole lot into the telescope and you should see images 3x bigger. Not necessarily as sharp though if you use too much magnification.

Optically it trebbles the focal length of the scope so the 350mm ETX70 becomes a 1050mm focal length f/15 scope. How exactly it accomplishes this optically I dont know.

The one in the box works fine, it does not induce more colour into the image, and once you dont use the smallest eyepiece the images are still sharp. The best comparison I have is with the 2x meade barlow and it seems to perform as well as that using the 2 larger eyepeices in the box.

I did try using a 5x powermate in the ETX-70, but that was overkill and looked it!

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Optically it trebbles the focal length of the scope so the 350mm ETX70 becomes a 1050mm focal length f/15 scope. How exactly it accomplishes this optically I dont know.
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I like your explanation. AFAIK Barlows don't do much more than put a negative lens between the eyepiece and the objective to effectively increase the focal length of the objective. They can be useful. Here is one thing I learned recently. Why would you use a 2x barlow with a 12mm eyepiece when you already have a 6mm eyepiece? You do lose a bit of image quality with the extra glass between you and the star, but what you gain is eye relief (distance between the eyepiece and your eye). So if you wear eyeglasses you might appreciate the extra bit of eye relief a barlow can give you.

Barlows got a bad reputation from the single element plastic barlows included with cheap telescopes so the manufacturer could boast "675x" for a 60mm refractor. (but they were able to make venus look like a psychodelic rainbow!)