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View Full Version : Barlow Benefits?



MatthewE
2003-Dec-29, 09:24 PM
Hey Guys, quick question, is there any benefit to using a barlow besides getting 2x or 3x the power? i remember hearing it helps to reduce unwanted light or something such as light pollution, can you please help clairify this for me, i currently have the Celestron Eyepiece set with the 32mm, 25mm, 15mm, 10mm,9mm,6mm and 4mm EP with a 2x Barlow, and the 7 filters.

Thanks.

Stéphane
2003-Dec-31, 12:40 PM
Hello. Sorry for my bad english :unsure:

The barlow lens, beside the magnifying effect you said, can be handy to picture moon and planets with a SLR camera or webcam. Having fewer lenses than common eyepieces, the barlow lens gives sharp pictures without the hassle of mounting the so-called "telephoto" system by Celestron.

This is the main reason why you can find even 5x barlow lenses on 2".

Edwin
2004-Jan-07, 09:31 AM
Hi There

Our local group is getting into web cam in a big way and we are all using Barlows to increase the focal length of our telescopes.

I must admit though that I very rarely use the Barlow when doing normal observing as I find that the definition is reduced.

Should you have one in your set? Yes
given the choice between a 20mm eyepiece with a 2x Barlow or an eyepiece of 10mm I would choose the eyepiece.

All the best
Ed

Dave Mitsky
2004-Jan-08, 03:00 PM
Originally posted by MatthewE@Dec 29 2003, 09:24 PM
Hey Guys, quick question, is there any benefit to using a barlow besides getting 2x or 3x the power? i remember hearing it helps to reduce unwanted light or something such as light pollution, can you please help clairify this for me, i currently have the Celestron Eyepiece set with the 32mm, 25mm, 15mm, 10mm,9mm,6mm and 4mm EP with a 2x Barlow, and the 7 filters.

Thanks.
A Barlow lens will not "reduce" light pollution to any greater degree than using an eyepiece of equivalent focal length. Boosting the magnification increases "contrast" so that in sense the ill effects of light pollution are somewhat lessened whenever power is increased. (Since the greater light grasp of a larger telescope allows higher magnifications to be used, a larger aperture, despite the urban telescope myth stating otherwise, will outperform a smaller one whether the sky is dark or not - http://skyandtelescope.com/printable/howto...article_508.asp (http://skyandtelescope.com/printable/howto/scopes/article_508.asp) .) A Barlow lens will reduce astigmatism in poorly corrected eyepieces but won't do anything to correct the chromatic aberration, as is sometimes assumed, inherent with fast achromatic refractors.

Modern high quality Barlow lenses such as the Celestron Ultima, the University Optics Klee, or the Tele Vue Barlow cause little or no noticeable image degradation - see Myth #6 at http://www.televue.com/engine/page.asp?ID=141. The Tele Vue Powermates, which are not really Barlow lenses at all, are simply superb - http://www.cloudynights.com/accessories/powermate.htm

Dave Mitsky

jenda111
2004-Jan-20, 02:25 PM
Hello.
I have had a telescope(8inch f/6 reflector) for about 4 years.At first I had 2 eyepieces -32mm and 12.5mm and a 2x Barlow.I used it sometimes,but only to get 2x power.Now I have more eyepieces - 20,9 and 7mm.With observing I found that the Barlow lets you use,say 20 mm,
but unlike the equivalent eyepiece(10mm),the glass is larger,making observing easier.
Clear skies
Jenda111

moosemanuk
2004-Jan-21, 12:21 AM
I have an 8" Dobsonian with two eyepieces - 20mm and 10mm. In both eyepieces I suffer bad degradation of the image when using the barlow. Like an earlier post I would rather use the 10mm than the 20mm with the 2x Barlow - does anyone else experience bad degradation of image with the Barlow, or is it just me? :-) is it something I should expect anyway when using the Barlow?

Clear skies and peace to all
Moo$e

jenda111
2004-Jan-21, 01:36 PM
Hello again
I use a Barlow quite a bit,without degradation of image.Some Barlows have an apperture stop,to correct poor quality lens.If possible,try another Barlow,or try other eyepieces with yours.Some eyepiece designs work better than others,not to mention the $$$$ factor ;-)
clear skies
jenda111

Dan Luna
2004-Jan-22, 05:35 PM
I have no complaints about my Celestron Ultima 2x Barlow. I normally use it for videoing the Moon and haven't noticed any loss of image quality. If looking through the scope I find my 25mm plus Barlow much easier on the eyes than the 9mm eyepiece. The trouble with the 9mm it is has low eye relief so I have to take my glasses off to get my eye close enough to see through it. Then it's out of focus for anybody else wanting to look and I need to put my glasses back on to realign through the finder scope etc. :blink: