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  1. #1
    5bassist's Avatar
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    Default 2 Barlows at the same time



    Just a thought.I have a 2x and a 3x Barlow.Would there be any advantage,or indeed,disadvantage of using both at the same time.ie 2x into 3x and then eyepiece into 2x? What would be the overall magnification is this case,or is it just a stupid notion?
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  2. #2
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    Default

    I've done it with my camera. I used a 2X 2 inch and a 3X 1.25 inch.
    Keep in mind that the more magnification you use the darker the object appears because the light is spread over a larger area. Then more glass means the likelyhood of introducing more errors in the image.
    2X and 3X used together would be 6X.
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  3. #3
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    Default

    To a first order, a 3X Barlow and a 2X barlow will produce about 6X magnification gain (+/- 20%) and might be a little dependent on which order the Barlows are assembled.

    Unless you have a really low power EP (40mm+), this combination will be very likely to have too much magnification for the atmosphere most nights.

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    Default

    Fair enough guys.The only other downside would probably the actual physical size (and weight!) of such a combination.Might give it a try anyway.See what happens.
    Keep Music Live!

  5. #5
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    Default

    I have done this with a 2X 2 inch and a 2X 1.25 inch barlow with mixed results. With some eyepieces your eye position starts to become critical. The image will black out if you are not in the exact correct position. Some eyepieces seemed to take it very well. Both barlows need to be of good quality, that having been said if they are of the same size (both 2 inch or both 1.25 inch) the better of the two should go into the focuser first. The barlow of lesser quality will work better because the light cone will not be as steep.

  6. #6
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    Default

    Quote Originally Posted by 5bassist View Post

    Just a thought.I have a 2x and a 3x Barlow.Would there be any advantage,or indeed,disadvantage of using both at the same time.ie 2x into 3x and then eyepiece into 2x? What would be the overall magnification is this case,or is it just a stupid notion?
    Not stupid if you like the results - tell us how it works out.

    I was convinced in this forum to avoid Barlows. The feedback was "they will still be for sale as long as people buy them". Since then I just bought a 4mm and 5mm eyepiece pair that gives me the most magnification my scope can handle - and even still I wind up using my 10mm more.

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  7. #7
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    Default

    I like barlows, I use mine a lot.

    I think a lot of the anti barlow thought is a hold over from an earlier day when barlows were almost all pretty bad.

    Another thing I have noticed is that many of the people who diss barlows have a lot of eyepieces in their case and have gotten used to eyepieces that are tailored to each specific type of viewing. They see and are bothered by things that us normal guys with a barlow and 5 eyepieces are simply not aware of and so not bothered by.

    This is not a bad thing I hope to one day have the chance to be just like them but advice coming from that perspective really may not be totally on target for those of us who are limited to more modest equipment.

    Until I can afford to pay more for my equipment than I did my car it is probably better I do not know what I am missing.

    The one TeleView eyepiece I received as a gift has already begun to effect me, that Garrett SWA just does not look as good as it once did!

    Back to barlows when I put one of mine in I really can't see any image degradation and I have very modest barlows. (zhumell 2 in ED and GSO 1.25 2X)

    My advice for a guy starting out is don't be afraid to get and use one.

  8. #8
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    Default

    Sadly it multiplies the focal ratio as well so an F10 scope becomes an F 60 scope and then you struggle to see ANYTHING.
    so a 20mm lens becomes a 3.6mm lens!!!!!!! Too much for most scopes straight away!
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  10. #9
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    Default

    I tried t edit my post but I waited too long.

    I do think there is a price point below which you are pretty much assured to get something close to useless. I have a name brand "economy barlow" that cost about eight dollars. I plan to use it as part of a DIY artificial star. I would never want to be forced to look through it!

    f 60 is getting up there pretty high!

    I may be a bit off topic. I will stop now.

  11. #10
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    For plossls and simple EPs a barlow is fine.
    For wide FOV EPs and more complex EPs, I do not use a barlow.
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