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I dont know how to use my barlow lens

The guy in the video says that i dont need the barlow lens and keep practice on my telescope but i want to increase my view by using them

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I use a barlow lens quite a bit with my telescope. It is usually inserted before the diagonal if you use one or before the eyepiece if you don't. The barlow lens for your telescope will double the power of the eyepiece used.

However, despite what the manufacturer claims for your telescope things will look quite poorly if you try to view at 180 power. Generally you'll get the best images by using 50x for each inch of your objective lens. For example, your telescope has a 50mm lens. That's roughly 2 inches. 2 inches times 50x gives you a maximum useful power of 100x. Depending on the viewing conditions you may be able to exceed this or not even reach it. Things will look blurry and dim when you try to use too much power.

Your power or magnification is calculated by dividing your telescope focal length which is 360 mm by the eyepiece focal length. You have two eyepieces with focal lengths of 4mm and 20mm. If we divide 360mm by 20mm we get 18 power. If you add a barlow to that you get 36 power. Dividing 360mm by 4mm (no barlow) we get 90 power. That would be your maximum useful power.

Therefore, you should be able to used the 20mm eyepiece with or without the barlow but the 4mm should only be used without the barlow.

I hope all of the math wasn't confusing.


Posted on Mar 25, 2009


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We receive more complaints on that brand than just about any other. There are two types of scopes.

A refractor with a lens in front and a focuser on the back--- and a reflector that uses mirrors.

For a refractor-- insert the diagonal onto the rear of the scope and then put the eyepiece into the diagonal-- DO NOT USE the 2x barlow. Take it out in the day time and practice focusing on a distant object.

If it is a reflector-- just put the same eyepiece into the focuser -- do not use the 2x barlow if you have one. Again take it outside during the day time and practice.

Read this:

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The barlow may be too much magnification for that aperture telescope. The higher the magnification the SMALLER the sweet spot is in focus.

Turn the knob slower and also practice focusing during the day time on a distant object.

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You are using too much magnification. Put the eyepiece with the largest number written on it into the telescope. DO NOT use the 2x barlow if you have one. Take it outside during the day time and practice focusing on a distant object.

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This is a simple small refractor telescope. Put the eyepiece with the largest number written on it into the telescope. DO NOT USE the 2 x barlow if you have one.

Practice focusing on a distant object during the daytime- you are not focusing the scope properly.

Here is Tasco's manuals web site:

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This is a barlow-

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You mean TELESCOPE not microscope.

Do NOT use the 2 x barlow.

Put the diagonal into the telescope, then put the eyepiece with the largest number written on it into the diagonal. Go outside during the day time and practice focusing on a distant object.

Read my TIPS on my profile page.

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Put the eyepiece with the largest number written on it into the diagonal WITHOUT using the barlow and note how much easier it is to focus.

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It multiplies the normal magnification of each eyepiece THREE times! In your small telescope you will probably never be able to use it. Magnification is the least important quality of a telescope.

Use the eyepiece with the largest number written on it, which is your LOWEST magnification. Practice focusing on a distant object during the day time. At night the moon should be your first target.

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DO NOT USE THE barlow. Put the eyepiece with the largest number written on it into the telescope. Practice focusing on a distant object during the day time.

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Do NOT use the barlow lens-- put the lowest magnification eyepiece into the scope-- practice focusing on the moon -- turn the focus knob slowly in and out until you get a sharp image.

Telescopes only show an area of sky about 1 degree wide or LESS--- this is about the size of the TIP of your finger held at arms length................ your scope is best used at low magnification.

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