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Eye piece size?

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Hey everyone,

I've been surfing ebay (mainly for astronomy stuff) and I notice that there are different sizes of eye pieces. How do I know what size mine takes? The manual doesn't say.

I was also wondering if its worth it to buy a converter?

Thanks in advance.

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Hello "Driftwood"

What make is your telescope?

Most modern commercially available scopes take 1.25 inch eyepieces (This is the standard size that is widely available). Your scope may have a focuser fitted which has a part that can be removed to allow the scope to take 2 inch eyepieces.



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I've just looked at an advert for it here:-


It's a 80mm Newtonian Reflector with a tube length of 800mm.

It advertises the scope as having a "multiple" 1/14" eyepiece holder which can take up to three eyepieces.

The advert says the scope comes with a 6.8mm to 16mm Zoom eyepeice, with a field of view of 42 degrees. Also a 20mm eyepiece with a 52 degree field of view, and a 3x Barlow.

So the scope does take the standard 1.25" eyepieces.

Your scope has a Main Mirror diameter of 80mm. This will cope with a maximum magnification of about 160x.

Magnification os worked out by allowing 50x per inch of aperture (mirror diameter).

Your scope has an 80mm (3 1/4" inches).

To get the magnification a particular eyepiece will give can be calculated by dividing the scopes focal length by the focal length of the eyepiece.

Your scope has a focal length of 800mm, so 10mm eyepiece will give you a magnification of 80x (80 times). If you have a 3x Barlow, it will triple that magnification to 240x. This the theoretical maximum for your scope, and would only be useable on the clearest of nights.

A 20mm eyepiece would give you 40x (800 divided by 20 = 40). Fit the 3x Barlow

and you would get a magnification of 120x, which again is a very high magnification for that size of scope.

A 30mm eyepiece would give a magnification of 26.5x. The 3x Barlow would raise this to 53x.

When you say your are wondering whether it's worth buying a converter, do you mean something to allow you to fit 2 inch eyepieces?

If you do, then you would need to check if your scope would allow you to fit one. Looking at the information I saw on the internet, it does not look like your scope will allow you to fit a converter.

I don't know what eyepieces you have with your scope, but I would tend to stick with say one eypiece of 10mm (for use on Moon and Planets - but only under the clearest of conditions!). An eyepiece of 20mm, again to give you good views of Moon and the likes of Jupiter and Saturn. I would have an eyepiece of 30mm to give you "low powered" and wide field views of the stars.

I hope this helps



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