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  1. #1
    sandy's Avatar
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    Default OK Just Looked Through the Barlow Again...



    When looking through a barlow, is your intended object dimmer than with just an eyepiece?

    I am getting a crisper cleaner image with just the 25mm.

    I just went out to look at Saturn. With the 25 it is TINY, but can focus it clear. When I use it with the Televue barlow it seems harder to focus on. I got it clear for a second, than could not get it focused again. I did get a clear focus on the moon though...

    Another thing is it seems when using the EZ Finder the object is centered for the 25mm, but with the barlow it is not. Is that normal??

    I wasn't sure if something could be wrong or if it is me?? (Collimation looks good)
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    Hi Sandy! Your view,might be slightly dimmer,with the barlow,but not by much. If the object,in the finder is not exactly centered,just off a slight bit ,the barlow will show it as being off,twice as far.Hope that helped!

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    Default

    Hi sandy ... Also in addition to what astrobl was saying , by the time you get the barlow in the eathe has rotated enough that it will make a object look like it has moved ...Mabey ..As far as the focus issues go it could be the seeing conditions wernt the best .....
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    Default

    Hi Sandy!
    some of the cheaper barlows dont have the best coated optics so you do lose some of the light through them but the better ones should have good coated optics, and you shouldnt lose much of the light.

    Televue makes a great barlow, but maybe your seeing conditions were not the best for that high of a magnification. Have you tried viewing on a different night?
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  5. #5
    sandy's Avatar
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    Default

    I tried a couple weeks ago, looking at Jupiter but couldn't get it to focus. It was low on the horizon so I thought that was the issue. I think Saturday is the next chance to look. It is supposed to be lower humidity and temps so will give it another shot and let you guys know how it turns out!
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    Sandy,what is the lenghth of your,barlow? If it is longer than 4" then,it is the type,that has a really small lens inside. If that is the case,then,that would really cut down on,your light,and your field of view!

  7. #7
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    Default

    Just wanted to add this. A barlow is used to increase magnification. As your magnification goes up, your exit pupil becomes smaller and hence the object will become dimmer.

    Also, your focus issues could be due to air turbulence (which is more pronounced at higher magnifications). This might explain why it is easier for you to focus on the Moon then on Saturn. Saturn's features are much smaller, so more noticably smeared by turbulence.
    Craig
    Last edited by caheaton; 07-31-2009 at 02:59 PM.

 

 

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