Question about Bushnell 675x5 EQ Reflector Telescope
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.
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
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
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
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
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
A Barlow lens doubles (or trebles) the magnification, but it also degrades the image. You are better off without it. People tend to buy telescopes on their magnification figures, even though these are essentially meaningless, so junk like Barlows get added to the package to increase the advertising impact. The mere fact that one came with this telescope tells you that the quality is not wonderful.
The specification that means something in a scope is the diameter of the objective (the main lens or mirror). Magnification is just the focal length of the objective divided by the focal length of the eyepiece. You can usually see more at lower magnifications, as the resolving power of the objective is often less than the advertised magnification. A smaller distinct image is better than a big blob of fuzz. That's why you were advised to try the scope first with the larger number (lesser magnification) eyepiece.
But try out the Barlow and see for yourself.
Posted on Nov 19, 2010
Testimonial: "Never heard "barlow" before; and this old man will have to look up "focal length" again. Thanks for your help; I appreciate your time & talent."
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