lenses. 10x 20x

[aussie_finder (Ryan)]

Ive got a telescope from Australia geographic store and it came woth 10x and 20x lenses, can u get different ones ? I was looking at Jupiter the other night and i wanna be able to see it abit bigger,

Any help or information would be great

[barx1963 (Malcolm)]

Hi Ryan
What sort of scope is it? Secondly, I am gusesing what you have is a 20mm and a 10mm eyepiece. The magnification provided by your eyepiece is worked out by dividing the eyepeice focal length by the focal length of the scope.

So if you have one of these http://shop.australiangeographic.com...telescope.html then the 10mm will give 650/10 = 65X and the 20mm one will produce 650/20 - 32.5x

You can get more "powerful" eyepieces but their effectiveness is limited by the scope itself, in a small scope the high power eyepieces are not as effective.

If you are not sure about the scope, perhaps post a picture of it.

Cheers

Malcolm

Originally Posted by aussie_finder

Ive got a telescope from Australia geographic store and it came woth 10x and 20x lenses, can u get different ones ? I was looking at Jupiter the other night and i wanna be able to see it abit bigger,

Any help or information would be great

[aussie_finder (Ryan)]

Heyy malcolm thanks for the help the telescope i got is http://shop.australiangeographic.com...pe-bundle.html

[Somnium (Aidan)]

Hi Ryan, you can also get a barlow lens which magnifies the image, something like this
http://www.bintel.com.au/Eyepieces-a...oductview.aspx

but as Malcolm mentioned the quality of the image and the amount you can magnify is going to be limited by the size of the aperture of the scope and the quality of it. you will always want a bigger and clearer image, that is why we get aperture fever

[AEAJR (Ed)]

Eyepieces come in 3 diameters, .965, 1.25 and 2 inch

Your scope is most likely using .965" or 1.25" eyepieces.

We need you to measure the diameter of the hole in the focuser where you place the eyepiece. Or measure the outside diamater of the barrel of the eyepiece at the end that goes into the telescope. It should be about 1" or 1.25". Then we will know what kind of eyepieces you can use.

There is no hard and fast rule but a general guide line is that maximum practical magnification is about 2X the aperture in mm. So a 70 mm scope would suggest 140X as a practical max magnification, but there is no law that says you can't try higher.

--------------------------------------------
Specifications:

Optical Design: Refractor telescope
Aperture: 70 mm (2.76in)
Focal Length: 900 mm
Focal Ratio: 10
Eyepiece 1: 20 mm (0.79 inches)
Magnification 1: 35x
Eyepiece 2: 10 mm (0.39 inches)
Magnification 2: 70xFilters:
Moon Filter included -
==========================

Something seems to be off on the specs. The specification says focal length 900 mm.

A 10 mm eyepiece used with a 900 mm FL scope would yield 90X. But they report it as 70X.
A 20 mm eyepiece used with a 900 mm FL scope would yield 45X. But they report 35X.

That would suggest the FL is 700 mm. The focal ratio of 10 would also suggest 700 mm FL so i think the focal length spec is wrong.



To get this 700 mm focal length scope to 100X you would need a 7 mm eyepiece. A 5 mm eyepiece would take you to 140X. Depending on the quality of the optics, the eyepieces and the mirror in the diagonal that might be as high as you would want to take this scope, although there is nothing that says you can't try higher.

The highest magnification you can really use on any scope will be dependent on the viewing conditions, the atmosphere, and the brightness of the object you are viewing. You might get Venus, Jupiter, Saturn and the moon up to 140X in that scope. Dimmer objects would likely look better at lower magnifications.