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  1. #1
    NCAstronut's Avatar
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    Default Which Barlow For Imaging



    I been looking at barlows, and I'm not sure which power to get. a 2X, or 3X. My scope is a Orion Astroview 6 eq. 750mm Focal Length,
    And I'll be useing my Philips SPC900NC webcam for the time being.

    Thanks

  2. #2
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    Default

    Easy to start with a x2 Barlow, cheap and cheerful. Later on you can look at higher mag' barlows.

    Clear Skies

    Pete
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  3. #3
    NCAstronut's Avatar
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    Default

    This is the one I have in mind.
    1.25in. 3x Orion HighLight 5-Element Barlow Lens | Orion Telescopes

    I only want to buy once, and get the right thing to start with. No money to waist. Also I plan on getting a Good Zoom Eypecice latter.

    Hey does installing/useing a barlow change the focal lenght? Will it effect where I usely get a target such as Jupiter in Focus? When I put the barlow in and drop my webcam in, will I have enough focus in either direction to get the target in focus? Sorry I just asked three questions of the same princable to be sure to get the correct awnser.

    Thanks
    Last edited by NCAstronut; 07-17-2010 at 10:51 PM.

  4. #4
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    Default

    that's a serious barlows.all i can add is try to make sure you
    don't overdo things on power.first find out what the limits are
    for your scope.having a 3x doesn't mean it will be useful for
    every ep.
    clear skies,
    andy

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    NCAstronut's Avatar
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    Default

    Quote Originally Posted by andyp180 View Post
    that's a serious barlows.all i can add is try to make sure you
    don't overdo things on power.first find out what the limits are
    for your scope.having a 3x doesn't mean it will be useful for
    every ep.
    clear skies,
    andy
    My scope's highest magnification is 300X

    I'm not sure how much magnification the webcam will add thou. But with a 10mm eyepeice and this barlow will yeild 225X

    750mm ÷ 10mm =75X Plus a 3X Barlow = 225X

    Wander what my scope and this barlow, with a Philips SPC900NC will yeild?

  6. #6
    NCAstronut's Avatar
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    Default

    I found my awnser.

  7. #7
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    Default

    hey nc

    given your scope is 152mm @ 750mm and your saying that the max is 300x, that would be 50x per inch at very good seeing. 300 is hard to get, i would use a practical measure lets say
    30x per inch=180x. now if you get a 3x barlow should give you almust the same mag about 200x, now if you gona buy a barlow id go with a televue, and there prices are very low . specs for telvue barlows focal length is 2x is 74.4mm and the 3x is 52.3mm.
    i got one a few years back and never looked back awsome barlow!
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  8. #8
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    Default

    Quote Originally Posted by ozzmozizz View Post
    hey nc

    given your scope is 152mm @ 750mm and your saying that the max is 300x, that would be 50x per inch at very good seeing. 300 is hard to get, i would use a practical measure lets say
    30x per inch=180x. now if you get a 3x barlow should give you almust the same mag about 200x, now if you gona buy a barlow id go with a televue, and there prices are very low . specs for telvue barlows focal length is 2x is 74.4mm and the 3x is 52.3mm.
    i got one a few years back and never looked back awsome barlow!
    I'm not aiming at 300X Thats the highest maximum useful magnification my scope can be used at.

    With a 10mm eyepeice and a 3X barlow will yeild 225X thats well under 300X and should not be a problem.

    I think a 3X with my webcam will be right on the money.

    What I want to figure out is this> With my telescopes 750mm focal length, and a 3X barlow, how much magnification will it be useing my webcam?????????????????????
    How can I figure out what the webcams power or size in mm is, like comparing it to a 10mm eyepeice.
    Last edited by NCAstronut; 07-18-2010 at 09:17 PM.

  9. #9
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    Default

    .....webcam and barlows tells me you're thinking of planetary imaging - if I'm correct with this presumption you'd be better off getting a 2X barlow and using extension tubes.....with a 2X barlow you'll get up to 3.5X with 100mm of extension tube (and anything in between by varying the ET length.)

    I use 2X, 3X & 5X barlows (the 5X being a Powermate) and with these on the C11 I can get anything at all from 2X to 7.7X

    For my money the TeleVue barlows are extremely hard to beat.....if your scope is a 6" job then undoubtedly the 2X barlow and extension tubes would be your best option....!

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    .....ps: there are tables that will calculate image scale/focal lengths to relative magnification.....do a search on said, but I think Anthony Wesley (bird) also has something on his website on this.....

 

 
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