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  1. #1
    Soliddriller's Avatar
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    Default eyepiece selection?



    hello all.i was wondering about barlows.do i lose clarity for example if i use a 5mm ep and then use a barlow? seems like if ep's are made as small as 2mm or so up to 40mm+ then why should i use a barloiw?i guess most folks seem to think it'll save costs as well as ep's.it seems to me that a barlow "magnifies" the subject but decreases in clarity.im considering buying a wide range of ep's from 2mm up to 40+mm in high grade optics.the more i speak with or text you guys the more you say to research and buy the best ep for what i wish to view.i would appreciate your comments as well guys. thanks and clear skies!!
    Skywatcher 10" collapsible dob (2x barlow-10mm & 26 mm eyepieces-extension tube)my ep's are 1.25"

  2. #2
    WWPierre's Avatar
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    It's probable that the average astronomer would see little difference between the views through, say as an example, a barlowed 24mm, and a 12mm of the same FOV.

    I have a pretty cheap barlow, and that is my experience.

    By the time you get down to 2mm, that target is gonna be really scooting across your FOV.
    Last edited by WWPierre; 03-28-2010 at 05:45 AM.
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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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  4. #3
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    Quote Originally Posted by WWPierre View Post
    It's probable that the average astronomer would see little difference between the views through, say as an example, a barlowed 24mm, and a 12mm of the same FOV.

    I have a pretty cheap barlow, and that is my experience.

    By the time you get down to 2mm, that target is gonna be really scooting across your FOV.

    You know....if you choose the focal length of your eyepieces wisely, with a barlow you can save money by buying only half as many eyepieces as you would without a barlow. That's what I did. I call my 2x barlow my "in-between" eyepiece!
    Name: Eric

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  6. #4
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    Also, some folks use them because they are able to retain the eye relief of their longer f/l eyepieces.

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    Quote Originally Posted by Soliddriller View Post
    it seems to me that a barlow "magnifies" the subject but decreases in clarity=
    In my experience as an "average astronomer" [whatever that means], the negatives of using a Barlow lens are most pronounced with faster (lower f number) telescopes (which means usually larger aperture Newtonians).

    I have looked at this issue extensively with careful head to head studies using an 8 inch reflector [Orion XT8i; report forthcoming]. My conclusion is that the small differences I have seen using a Barlow lens [Celestron Ultima] are due mainly to decreased light transmission vs impairment of clarity--hence, this become a real phenomenon when attempting to detect the fainter moons or faint colored bands on (for example) Saturn. That being said, for very fine detail work on double stars when attempting reach the Dawes limit--a Barlow lens may add sufficient fuzziness so as to make it a poor choice [versus a lone eyepiece] when added to the optical train.

    Others on this forum have reported detrimental effects on clarity (fuzziness) when using their Barlow--if you do decide to purchase a particular brand, try to read as many reviews as you can.

    Retainment of eye relief using a Barlow as mentioned by Griffin is a huge plus for many and must be considered (particularly those who observe wearing eyeglasses).
    Last edited by MarkM; 03-28-2010 at 02:27 PM.
    Location: 30° 19' N; 97° 54' W; elev 248 meters; yellow/green zone; NELM 5.7
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  9. #6
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    That is my experience with using barlows. The Orion Shorty-Plus in my opinion was terrible and it gets fantastic reviews. It definitely distorted my images and decreased light by quite a bit. I sold it and replaced it with the Televue 2x barlow and it was definitely an improvement. The images are not distorted and keeps everything relatively clear, however it still steals light. It almost feels as if I have the Ultrablock filter on while using it. As of right now I have staggered EPs and the barlow for cost effectiveness, but eventually I'll keep adding EPs and the barlow will be a dust collector.

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    Quote Originally Posted by TCA View Post
    the barlow will be a dust collector.
    Unless you decide to implement the Barlowed laser technique for collimation.
    Location: 30° 19' N; 97° 54' W; elev 248 meters; yellow/green zone; NELM 5.7
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    Quote Originally Posted by MarkM View Post
    Unless you decide to implement the Barlowed laser technique for collimation.
    Yeah, I'm looking for a good night collimation tool. Do you have any suggestions? Been looking at the Glatters.

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    Quote Originally Posted by TCA View Post
    Yeah, I'm looking for a good night collimation tool. Do you have any suggestions? Been looking at the Glatters.
    I own a Howie Glatter single beam, 1.25" version. It is excellent!

    Very useful for not only barlow but also in place of sight tube to align diagonal. **Also, the underside of this laser now has a white surface which obviates the need to place a paper circle over the barlow (something I hate doing) in order to see the reflected centering device (donut, triangle, etc.)
    Location: 30° 19' N; 97° 54' W; elev 248 meters; yellow/green zone; NELM 5.7
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    Quote Originally Posted by MarkM View Post
    I own a Howie Glatter single beam, 1.25" version. It is excellent!
    Nice, I'll check it out. I have a few other purchases in front of it though.

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