What would be the right erect image prism diagonals to get for a vivitar 76mm Reflector telescope

All astronomical telescopes show upside down and or inverted images-- it's completely normal. To use this for terrestrial viewing (klijke a spotting scope) you will need to buy the correct size erecting prism diagonal similar to this one:

http://www.agenaastro.com/william-optics-1-25-45-erecting-prism-diagonal.html

All astronomical telescopes show upside down images. For terrestrial viewing you can buy an erecting diagonal--
http://www.highpointscientific.com/product/ORI-08787/Orion-125-90-Degree-Erect-Image-Star-Diagonal-08787.html

Read my TIPS and frequently asked questions on my profile page.

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".

If the telescope has a standard 1.25 inch diameter eyepiece, then an erecting eyepiece may be found on Amazon or eBay. An erecting prism or diagonal of the type that bends the light through 90 degrees is not right for a reflecting scope. These are used on refractors.

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. For a reflector, an erecting diagonal of the kind that is often used on a refractor is of no use. There are other types of erecting adaptors or eyepieces. However, unless you wish to use the telescope for terrestrial viewing, for which a reflector is badly suited anyway, you might as well fall in with the tradition that astronomical observations are made upside down.

The scope has upside down images--- all astronomical telescopes do this it is normal.

You can buy an "erecting prism diagonal" for this scope if the focuser hole is 1.25 inch-- here:

http://www.amazon.com/Meade-Degree-1-25-Inch-Erect-Image-Diagonal/dp/B001NKP5WE

Turn the diagonal, and the image rotates. Using the scope for star gazing it does not matter. Normally an astronomical telescope shows an upside down image--- no up or down in space. The erecting prism is only used for terrestrial viewing as the prisms inside are probably NOT multi-coated.

All astronomical telescope show upside down images. It's normal, nothing is wrong with your scope. You can buy an "erecting prism" diagonal for terrestrial viewing.

See my TIPS on my profile page.

Dopn't worry about upside down. All astronomical telescopes show images upside down. There is no up or down in space.

You may have what is called an "erecting" prism diagonal that turns the image right side up. Just Google "erecting prism diagonal".

This may also help you.
http://www.cloudynights.com/item.php?item_id=810

All astronomical telescopes show upside down images. You would need to add an additional "erecting prism" to turn them right side up. This just puts more glass between you and the dim sky image. You can buy an "erecting prism" from many on line retailers.

Here is one:

http://www.astronomics.com/main/Image_Erecting_Prisms.asp/catalog_name/Astronomics/category_name/EDNECFUVSRWS8KLNTU5E38XSE1/Page/1

You do not need an erecting prism to view objects at night. These are used if you wish to view terrestrial objects since it turns them right side up.

If you have a reflecting telescope (it uses mirrors) it's normal to not use an erecting prism or as they are also known as star diagonals. Objects will appear inverted and that's normal. A refracting telescope (no mirrors, just lenses) will also invert the image but it is quite often used with a star diagonal to make it easier to view. There are many other types of telescopes that use a combination of mirrors and lenses.

I hope this helps.

-jodair