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Hi, a few years ago I received a telescope, a vivitar 76700. I have a 2x barlow, an erecting eyepiece, a 20mm lens and a 12.5mm lens. 

When I try to put it together, nothing quite fits. I can get the lens into the erecting eyepiece and the barlow into the telescope, but I cannot fit the erecting eyepiece either directly into the telescope or the barlow - it's too small and therefore doesn't perfectly line up which is preventing me from seeing anything.

Am I missing any pieces? Am I doing something stupid?

Any help appreciated :)

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Hi. Could you post pics of your gear? Pics where dimensions are clearly seen, that means components must be shot at the same distance, to avoid the illusion of wrong sizes due to perspective. I was thinking of googling images of the standard accessories in a Vivitar 76700 package, but your set is not necessarily standard.

Or measure the nosepieces: modern size is 1.25" (31.75mm), but some older, obsolete accessories in 0.965" (24.5mm) are still around. Could be some of your accessories are mismatched. Wouldn't be a tragedy because lots of unexpensive replacements are easy to find.

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There are more informative people on here but I would try just an eyepiece first if you cannot focus on anything I would then swap the eyepiece for the erecting eyepiece and the 20mm eyepiece to see if you can focus then if you can you should be able to place the 20mm in the barlow and then the barlow in the erecting eyepiece making it a 10mm. 

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10 hours ago, Ben the Ignorant said:

Hi. Could you post pics of your gear? Pics where dimensions are clearly seen, that means components must be shot at the same distance, to avoid the illusion of wrong sizes due to perspective. I was thinking of googling images of the standard accessories in a Vivitar 76700 package, but your set is not necessarily standard.

Or measure the nosepieces: modern size is 1.25" (31.75mm), but some older, obsolete accessories in 0.965" (24.5mm) are still around. Could be some of your accessories are mismatched. Wouldn't be a tragedy because lots of unexpensive replacements are easy to find.

Ah yes, I think my pieces are different sizes! My telescope and barlow are 1.25" but the rest seems to be the smaller size. 

Do you have any recommendations as to where I can go to get replacements?

Thank you!!

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Looks like the erecting eyepiece is undersize, but that's not a problem for an astro telescope, there's no up and down in space, and all newtonians have upside-down images because adding lenses, especially super-cheapo ones, robs some image quality.

And using a newtonian for terrestrial is not convenient because of the side-mounted focuser, so you can ignore the erecting lens, no stargazer ever employs one. Are you eyepieces marked "H=focal length", "HR=focal length", or "K=focal length"? H and HR are junk, but K is acceptable.

Good cheap "K" (Kellner) and "PL" (Plössl) eyepieces can be had in eBay and all the major astro stores. What country are you in? For a basic scope like yours unexpensive accessories only. When you attach a good eyepiece to a so-called toy scope, it feels much less like a toy.

Edit: you can add some improvised ring around the two eyepieces' nosepieces to be able to use them for the moment.

Edited by Ben the Ignorant
typo
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40 minutes ago, hitoka said:

Do you have any recommendations as to where I can go to get replacements?

There are plenty of places where you can get replacements. There are specialist astronomy stores in various places (which may tend to stock the more upmarket eyepieces that cost as much as your telescope), but if you shop online there are various reputable dealers in the UK and elsewhere. If you are on a tight budget look at 'astroboot' which carries lots of one-off and remaindered items. There is also ebay, if you are able to avoid the rubbish and the "bargain eyepiece sets". As your telescope appears to be a budget model with a long focal ratio you should probably stick to inexpensive Plossl eyepieces which should perform well in it. I suggest ditching the erecting eyepiece which is of questionable utility for an astronomical telescope and may not perform well. You will no doubt get other advice about what eyepieces to buy but something like a 25mm, a 12.5mm and 10mm, (no need to be exact) plus that barlow, should be a good start.

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Thank you all very much! I'll have a dig around for some lenses. This is the start of my astronomy!

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Personally, I would ditch the erecting eyepiece, use the money you would have spent instead on another eyepiece. In space there is no up or down and you will soon get use to the inverted image in the other eyepieces.

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