Question about Bushnell 675x5 EQ Reflector Telescope

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Focusing the Barlow lens

I have a 3x barlow lens that I can't see anything out off. This telescope was given to me. The 22x lens works fine. There is a tube that goes with the barlow lens, not sure what this is. Thanks for any help.

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  • Lee Sturgess
    Lee Sturgess May 11, 2010

    Hello first things 1st your barlow lens should be about 2 - 4 inches in length it consists of an eye piece screwed on to a tube,this barlow goes in the 1.25 inch hole (visual back) then your 22mm eye piece fits into the barlow,One thing will stop this from working is if your telescope is exceding its maximum useable magnification. In other words trying to magnify the image too much. You can calculate this by dividing the focal length of your telescope by the eyepiece, In this case 22mm. For example 900mm focal length divide 22mm eyepiece = 40x Magnifcation then include 3x barlow = 120x mag which should be fine with your telescope.Try screwing the tube onto the barlow then inserting the eyepeice into the barlow. Hope that helps Good Luck

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SOURCE: i dont know how to use my barlow lens

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.

-jodair

Posted on Mar 25, 2009

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The erecting prism can be used for both terrestrial and star gazing-- put it innto the scope first.

The 3x barlow probably will NOT be very useful... it triples the power of any eyepiece. Your small scope cannot go much over 100 power-- before the image degrades.

Put the eyepiece with the BIGGEST number written on it into the erecting prism which you previously stuck into the scope... now go outside during the daytime and practice focusing on a distant object.

The bigger the number on the eyepiece the LOWER the magnification.

Posted on May 16, 2009

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Posted on Aug 30, 2009

SOURCE: I don't know how to work my telescope I don't

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.

Posted on Nov 12, 2009

SOURCE: I have a 3x Barlow telescope that is completely

There is no such thing as a 3x barlow telescope. A barlow is a small accessory that multiplies the magnification of any eyepiece.

This is a barlow-
http://www.agenaastro.com/GSO-1-25-2x-Barlow-Lens-p/obar-gs-gs2bl.htm

Posted on Jun 01, 2010

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Just bought a starnavigator 114. Purchased a Barlow lens to use with my 26mm lens, but with the barlow I can't see anything. Do I need to make changes in the lens config. in the Autostar?


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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No the barlow increases the magnification by 3 TIMES for any eyepiece --
this will be too much for that small 76mm telescope.

Magnification is the least important quality of a telescope. Aperture and quality ioptics are much more important. I usually never use a barlow -- just the straight eyepieces in various mm sizes.

Read my tips on my profile page.

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The 3 x barlow will be useless for this small telescope.

Put the 1.5 x erecting PRISM into the telescope and then put the eyepiece with the largest number written on it into the erecting prism. This is your lowest magnification.

Take the scope outside during the daytime and practice focusing on a distant object. Turn the focuser knobs slowly until the object comes into sharp focus.

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What is the barlow lens for and how do i use it


It multiplies the normal magnification of the eyepiece. They come in 2x, 3x, 4x, and 5x powers.

Normally in a very small telescope like your scope, they are completely useless! They generate too much magnification for that small aperture.

You would normally put the barlow into the telescope, and then put the eyepiece into the barlow lens.

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There is no such thing as a 3x barlow telescope. A barlow is a small accessory that multiplies the magnification of any eyepiece.

This is a barlow-
http://www.agenaastro.com/GSO-1-25-2x-Barlow-Lens-p/obar-gs-gs2bl.htm

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I believe this is a refractor style telescope. Put the eyepiece with the largest number written on it into the telescope. DO NOT use the 2x or 3x barlow if you have one.

Practice focusing on a distant object during the day time. The moon should be your first target at night.

Read the web site listed below and my TIPS on my profile page.
http://www.texasastro.org/telescope.php

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The barlow is inserted into the diagonal and then the eyepiece is inserted into the barlow.

Try this during the day and practice focusing oin a distant object. I think you will discover that using the barlow gives to much magnification, and makes focusing very difficult.

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.

The maximum magnification for any telescope is 50 times aperture. So a 4 inch scope is 200 power. Usually you will never be able to get 50 times but only 30-40 times due to turbulence in the atmosphere.

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I don't know how to work my telescope I don't understand what the 3x barlow goes and what it is for I cant' see anything I tried to set up the crosshairs with the lens but can't figure it out and I have no...


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.

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You mean your 2x or 3x barlow. These can be purchased from many on-line retailers:

Here are two:

http://www.telescope.com/control/category/~category_id=barlows

http://www.agenaastro.com/Barlow-Lens-1-25-inch-s/66.htm

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Cant see anything out of it


These are known as toy telescopes. Put the eyepiece with the largest number written on it into the telescope. DO NOT USE the 2x or 3x barlow.

Go outside in the day time and practice focusing on a distant object.

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