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  1. #1
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    Default barlow 2 x dark view



    Hello,

    I am very new in astronomy, so pls forgive for my questions "too junior"

    I already have a barlow 2x which I believe is a very low quality one (brand Kion ???) and when I used it the view I got was much much less bright than without. It is barely acceptable with Jupiter and moon and abosolutely not feasible with everything else.

    Is it a problem common to every barlow and with mine it becomes very evident due to its poor quality or if I buy a good one (say a TeleVue) then I do not have a give up in brightness ?

    Moreover I thought that a barlow ( a good one !) was more useful for imaging than for viewing : can it be and affective substute to a large set of eyepieces. Am I correct ?

    thanks

  2. #2
    WWPierre's Avatar
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    Default

    A 2x barlow spreads the same amount of light over 3.14 times the area, so it has to be dimmer.

    (brand Kion ???)
    Probably Kson?

    I have a number of barlows, ranging from $10 to $110, which I have tested against each other in various telescopes. I have never been able to find any correlation between optical quality and price. The quality of all seems within a few percentage points, except for a Kson barlow I obtained from Telescope Warehouse; it gave me a noticably blurrier view.

    At one point I considered importing Kson products for resale on eBay. In view of your experience, together with mine, I'm glad I didn't.

    I recently bought a cheap Seben 2X plastic barreled barlow, simply to use as a spacer, after removing the element. On testing, I found it out performed ALL my other 2X barlows.
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  3. #3
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    Default

    yes KSON..

    Very interesting the results of your experience, I understand from it that an average product is fine, and that the additional marginal quality (when there is one) is not justified by the extra price.

    thank you

  4. #4
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    Default

    well...I am jumping aroung in the web shops and most of the Barlows trades at mid high 50 eurs ...with two big exceptions:
    Celestron Ultima
    TeleVue

    What do they have to cost almost twice ?

  5. #5
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    Default

    What do they have to cost almost twice ?
    Probably better glass - with coatings that are hightransmission
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  6. #6
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    Default

    2 3X barlows: Left cost $12, Right cost $110. View through left is 98% as good as the right one.

    The element is from a 2X barlow. It can be dropped into either of the other 2 to give a 5X barlow. I use my 30mm with this combination as a 6mm. Gives the same view as my 6mm UW, on right in second pic, but much more comfortable, with my glasses on.
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    127 Mak/go-to EQ5; Burgess 127f8 refractor; Sky-Watcher 5" F/5 collapsible dob; 90mm Mak/motorized EQ2; Royal Astro 76/910-GEM; Meade 60x700 refractor/alt/az; Zhumell 25x100 Coin Ops; GalilleoScope. Celestron 8mm-24mm zoom; lots of fixed EPs,some good, some..not so much. A small collection of surveying instruments; a forest of tripods; Canon Rebel Xti. Confirmed gadget junkie; Custodian of the Magnetic North Pole (Send $1.00 to Pierre each time you use a compass.)
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