Reassembling a tasco 14x 18mm erecting eyepiece

The different eyepieces are to give different magnifications. This is worked out by dividing the focal length of the telescope, f = 900, by that of the EP. So the 25 mm Kellner (that is the type of optics in the EP) will give 900 / 25 = 36 times magnification.

The erecting eyepiece is used for terrestrial viewing. Normally with an astro telescope everything is upside down as that does not matter when looking at a star. So when you want to look through someone's bedroom window you use this.

A Barlow lens is an add-on magnifier. If you add this onto any EP (it normally fits between the EP and the scope) it will increase magnification x 3.

There is a practical limit to what any scope will deliver, governed by its aperture (the size of the front lens) and for your scope this will be about x 120 magnification. Beyond that the image becomes too dim and fuzzy. This means that your 4 mm eyepiece ( x 225 magnification) won't be much use. It will be hard to find the object you are trying to observe, it will be hard to focus, and the image will wobble around. Nor is your barlow lens much use either I fear.

You might consider another eyepiece around 18 mm to give a nice spread. A Plossl type is good. If you get serious about astronomy, I think you will immediately want a better scope after using the Tasco.

Astronomical telescopes produce an upside down image. Buy an erect image eyepiece if you want to use the scope for terrestrial use.

The Barlow lens goes between the diagonal and an eyepiece. It doubles (2x) the magnification of the eyepiece used.It does this by halving the f/ ratio of the scope.
Eyepiece alone gives 35x; barlow with eyepiece =70x.

Note: this scope comes with an erecting eyepiece and is NOT suitable for atronomy use (other than perhaps the moon)

The eyepiece size (diameter) is the standard 1.25 in.
Erecting eyepiece adapters can be used with this scope.
maximum magnification is 250x therefore highest eyepiece would be 3.6mm
most useful magnification of any scope is 150x (900/150= 6mm eyepiece
Eyepieces provided with scope (Huygens type) have a narrow field of view and are relatively poor for astronomy but should be fine for terrestrial viewing

Astronomical telescopes usually show an upside down image. There is a good reason for this- erecting the image needs more bits of glass in the light path, which reduces the amount of light and increases aberrations. Even if this is only slight, astronomers prefer to avoid it, and they don't really care which way up the Moon or Jupiter appear.

It is possible to fit an erecting prism or eyepiece to most astronomical telescopes, and some of them come with one, but if you want a telescope primarily for terrestrial use, you are much better off buying what is called a "spotting scope".

The poor focus is harder to answer. Tasco scopes are not renown for their quality in the first place. You may simply be expecting too much, particularly if you believe the advertising blurb about magnifications of 300 or 500 times. These magnifications are simply not achievable in practice with a small scope. You should get acceptable results at lower magnifications, but the eyepieces supplied with these scopes are often of inferior quality and design. You can replace them with better ones, but these can cost more than the scope (if not, they probably aren't much better).

There is an excellent website for beginner telescope users at THIS LINK

Astronomical telescopes usually show an upside down image. There is a good reason for this- erecting the image needs more bits of glass in the light path, which reduces the amount of light and increases aberrations. Even if this is only slight, astronomers prefer to avoid it, and they don't really care which way up the Moon or Jupiter appear.

It is possible to fit an erecting prism or eyepiece to most astronomical telescopes, and some of them come with one. One type of erector will make the image appear right way up, but still reversed from side to side. That seems to be what you are using. If you want to use the telescope for terrestrial viewing, you will need a fully erecting eyepiece, or a fully terrestrial telescope (these are often called "spotting scopes").

All astronomical telescopes show upside down images, you must add extra glass to erect the image which will dim the images of deep sky objects in the eyepiece.

You can buy an "erecting" prism for terrestrial viewing.

Here:
http://www.agenaastro.com/GSO-1-25-45-deg-Erect-Image-Telescope-Diagonal-p/odia-gs-pd45.htm

Probably -- the 4mm gives too much magnification for you telescope-- difficult to focus or find thing in the sky-- you should also have had an eyepiece somewhere between 17mm and 24mm for lower power viewing.

Try the other eyepiece first-- no one can fix that scope which is imported. No repair facilities or replacement parts. Next time stay away from those types of scopes-- buy from one of these NORMAL scope retailers--

http://www.tasco.com/pages/instruction-manuals/


http://www.telescope.com/



www.telescopeman.org
www.telescopeman.info
www.telescopeman.us

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.