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Thread: Which barlow works with 100mm reflector?

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    Question Which barlow works with 100mm reflector?



    I recently bought an Orion Skyscanner 100mm reflector. It came with 20mm and 10mm lenses. It's a fast scope, F4, so the lenses alone don't give a lot of magnification.

    I would like to buy a barlow to get the magnification up to the 120-180x level for seeing basic lunar and planet features. I would guess that a 3x barlow might work best here.

    It's my understanding that some barlows won't work with this fast scope because the focuser won't travel enough to fully focus the image.
    Does anyone have this type of scope, and know what model of barlow will work with this scope?

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    I actually find this a very interesting question. Not sure you'll like what I have to say, however. . .

    You have a very fast telescope. To give you good views right up to the edge of your Field Of View (FOV) you would need some very good (read expensive) eyepieces or something like a Paracorr 2. These would weigh too much for your telescope and cost at least several times more than you paid for your telescope.

    Instead, Orion gave you two eyepieces which have 3 elements in each. This means that they didn't even give you Plossl eyepieces but probably Ramsdens. Ramsdens are really pretty lousy eyepieces and it angers me every time I hear of them being sold to the unsuspecting.

    The point I am easing up to is that your eyepieces are ill-suited to any telescope at all. Now a little caveat to that which is to say that while Ramsdens are pretty bad, they are better at fast telescopes than are Huygens (Huygens get horrible with telescopes which are faster than about F/12 - which are very slow telescopes. . .).

    Buying a Barlow will not rescue you from really bad eyepieces. In this case it will tend to make them worse eyepieces since the Ramsdens (I'm assuming that is what they foisted on you) tend to do better with faster optics. When you plug that 3x Barlow into the focuser you will have changed the telescope (in some sense at least) into an F/12 telescope which is where the Huygens start to be marginally acceptable and the Ramsdens are exceptionally pitiful.

    So you invest good money in a decent Barlow and you turn merely bad eyepieces into pitiful ones. I don't think this is a good investment.

    Then on to another point? Your telescope will not likely be able to utilize more than 100x except under exceptional conditions. Pushing your magnification to greater magnifications will likely just magnify your optical problems and atmospheric issues and make you wish you were watching a re-run of Matlock.

    In case you didn't notice, I hold out little hope for your eyepieces. But the telescope itself shouldn't be all that bad. If you get some decent Plossls you may be able to enjoy some decent on-axis views despite the ridiculously fast design of your telescope.
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    ^ Why not just say "Your telescope is fine, but the eyepieces that come with telescopes are like headphones that come with music players - discards."

    The eyepiece is a microscope looking at the mirror. Shorter eyepieces, say 5mm, will give higher magnification. Mag is focal length divided by eyepiece length. So your 400mm focal length scope divided by 5mm eyepiece equals 80x.

    But the reason you got a 20mm (20x) and a 10mm(40x) is because your mirror is only 100mm. Your scope excels at low-mag wide views of the sky. You can certainly use a barlow, but I'd buy a new eyepiece first. They didn't give you garbage, but the scope is the loss leader. Not good business to sell you a scope that won't benefit from better eyepieces.

    You should get incredible views of the moon as is. I see things clearly with my binoculars I never knew existed. Look along the terminator - the light/dark line - especially near the oncoming full moon. The full moon itself is not that exciting, IMHO. That line of shadow, however...

    Check out Orion, both the belt and his sword. If you go right from his belt, there is a bright star just about in line. Just below that is the Hyades, a group of stars in a vague hexagon pattern. Keep going right on the same line about the same distance again and you can see the Pleaides. Naked-eye it looks like a few stars. In a scope it's a little "Big Dipper" design, with as many dim stars as your scope can pick out.

    Get a better 20mm or 10mm eyepiece before you spend money on a barlow. You'll see more, better, with a better eyepiece, with or without the 2x lens. You don't have to spend a ton of money, less than $50 will improve the telescope greatly.
    Last edited by OneGear; 03-21-2012 at 05:09 AM.

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    Odd, all of my settings on this website are now in French.

    Anyways, I'm not sure these eyepieces are quite as bad as is assumed. They are the Orion E-Series that sell for about $25 each on the Orion website.
    Orion isn't clear about just what they are, as they are listed as "proprietary". I read they might be some kind of modified Kellner(sp?) design.

    I've been satisifed with the view I get from them so far. I can resolve stars down to fairly sharp points, seen Andromeda and Orion nebula, and seen four of Jupiter's moons. I've read on here that some have resolved Jupiter down to four bands using these.

    I do anticipate getting some better lenses down the line, but I'm going to have to start saving up the lunch money again first. Wife has first dibs on payday.

    I'd still like to hear what model of barlow folks have managed to use successfully with this scope.

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    Hi,

    The Orion Shorty 2x Barlow will work just find with your scope. Also, the GSO 2x barlow from Agena AstroProducts will work as well. A nice feature with both these barlows is you can unscrew the lens cell and screw it directly to the eyepiece. This gives you a 1.5x so you effectively have 3 mags with just one eyepiece.

    You are right in that these eyepieces are not that bad. I have the GoScope 80 Refractor with these same eyepieces. Using the 10mm with a barlow gives decent views.

    The attachment below is an article done by S&T magazine about Orion's Tabletop telescopes.

    Clear Skies,
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    Orion StarBlast 4.5 mounted on an Orion Tritech II Field Tripod

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    Quote Originally Posted by xplornevada View Post
    Odd, all of my settings on this website are now in French.
    .
    .
    .
    Toward the bottom left of the page you will find embedded within a blue bar a drop list which will allow you to change back to English. I had that happen once and someone had to point it out to me. . .
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