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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  • 36 Answers

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.


Posted on Mar 25, 2009


SOURCE: Bushnell Deep Space Series 525x 78-9500

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

SOURCE: Set up a Jason 307 Explorer Telescope?

Jason and Bushnell are the same company. Here is a list of the manuals. Find your telescope-

Look down the web page.

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-

Posted on Jun 01, 2010

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1 Answer

Vivitar 76mm reflector teles.76700 barlow lens 3x eyepiece is to small for there a reducer for the barlow ?kit came with two 3x barlow.same size

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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Sorry-- there are several different ways it could go depending on the barlow. NEVER disassemble an eyepiece or a barlow. Only the outside surfaces need to be cleaned from time to time.

Dec 30, 2010 | Tasco 49114500 Spacestation(r) 114mm...

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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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I have a 3x Barlow telescope that is completely disassembled and I need instructions on how to reassemble thee entire telescope.

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This is a barlow-

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Can't see anything through the lens on a Galeleo D76

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.

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We just got this ata yard sale and for some reason we cant see through it i dont know any thing about these but need some help please

Thanks for the additional info.

Your telescope is a basic introductory model and so has very limited performance, but used correctly it's still a great introduction to astronomy. If you don't have it, download the user manual from here (courtesy of Retrevo).

If complete, it should have come with a 5mm and a 20mm eyepiece, also an erecting tube (so called as it ensures images are upright and also laterally corrected: used for terrestrial viewing only), a diagonal mirror and a 3x Barlow lens.

Only use the erecting tube for daytime viewing of distant objects on land or at sea. The diagonal mirror is what you use for astronomy and it allows a more comfortable viewing position: without it you'd be trying to crouch beneath the telescope and craning your neck upwards to look into the eyepiece. Check that the mirror inside is bright and clean; if it's dirty or corroded then images will be low contrast, dim or even impossible to see. The eyepieces allow different image magnifications; the 20mm one has the lowest magnification, but also the brightest images and vice-versa for the 5mm. To calculate the magnification, divide the objective lens focal length (in this case 700mm) by the eyepiece focal length. For the 20mm eyepiece you end up with 700/20 = 35 and for the 5mm it's 700/5 = 140. If you then add the 3x Barlow lens you end up with 105x and 420x.

You're probably thinking, "OK, but how does this fix my problem?" As long as the diagonal is clean then your problem is almost certainly badly chosen eyepieces by the manufacturer: the greater the magnification, the dimmer the image, and realistically the maximum useful magnification for a 60mm objective in perfect conditions is 120x and more usefully is 30x to 60x and these limits apply to a good quality telescope. Meade, Tasco and a few others are built to price first, impressive sounding features second and quality a very distant third, so those limits can be comfortably reduced. All of this means that whilst the 20mm eyepiece may be capable of providing a useful image, the 5mm really isn't and the 3x Barlow will be low quality and far too powerful. Using the 5mm even without the Barlow is going to result in too high a magnification. As the night sky is mostly dark, unless the telescope is directly pointing at a bright star you'll see nothing. Although a magnified image will show planets as discs, stars are so incredibly distant that even at the unusable 420x magnification they will still appear as near invisibly dark pinpoints, and at 140x will be very dim pinpoints. I use the word pinpoint hesitantly, as in all but the best conditions the Earth's atmosphere will cause the star to twinkle, so the pinpoint will be a blurry blob. The only reason to include the 5mm and the 3x Barlow is marketing: to a novice, a 420x telescope sounds far more impressive than one which may be more expensive but which only offer 120x maximum magnification.

In short, don't use the 5mm eyepiece or the 3x Barlow at all. Stick to the 20mm and if you only have the 5mm then go and buy a budget 20mm and a 12.5mm. If you join a local astronomy club you may even be offered them free of charge as someone is bound to have upgraded to better quality examples. If you stick to these eyepieces then your telescope will be great for observing the Moon and will be able to see Jupiter's four largest moons (don't expect to see details on Jupiter though). It will also be able to show Saturn as a spot with ears sticking out either side (the rings) but you won't see any detail. Mars will be a noticeably red disc but lacking in much detail. Although you won't be able to make stars appear to be any larger, you are able to see how many of them are actually binary stars. You need to upgrade the telescope quite a bit to improve on those images, and also to ensure that you're viewing away from city lights if possible. It also helps immensely if you leave the telescope outside for a few hours before using it, as warm air currents inside the telescope tube itself can be enough to ruin images. As long as you understand the limits of your telescope then even as a budget model it will teach you a lot and show you things you haven't seen before.

One final tip: it can be awkward to get the focus adjusted correctly using the rack and pinion mechanism. Use it to get as good as possible, and then adjust the fine focus using the eyepiece itself: if you examine yours then you'll probably find that the actual lens assembly is simply secured to the eyepiece tube by a screw thread. By tightening the small screw on the diagonal to grip the eyepiece tube you'll find that you can fine focus by turning the eyepiece lens assembly itself back and forth.

Sorry for so much detail, but I hope that you now understand that your bargain find probably isn't faulty at all but just needs the correct eyepiece under the right viewing conditions. Please take a moment to rate my answer or to ask for clarification if anything I've written is unclear.

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1 Answer

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.

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

Here are two:

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Upside down images

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What lens do i insert into scope to view the moon

The moon is big so use the 25mm. The Barlow will have a multiplication marking on it 2x 3x etc. A 2x Barlow lens will effectively double the power of the eyepiece you are using. Do not use the erecting eyepiece for anything other than land viewing. Erecting eyepieces generally reduce the amount of light reaching your eye and thus reduce brightness of the faint objects in the sky.
So basically just place the 25 mm lens in the focuser and point the scope at the moon and you will be amazed at what you can see and how bright it is.

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