Telescope lens. F-number what one?
Discussion
OK. Here is a good start: I know sod all about F-Stops or numbers etc. But I purchased a telescope from a boot sale (Yeah, yeah Pikey and all that crap) anyhow the eyepiece is missing 
Its a Tasco 302012 Now, this chap is selling a load of them that he says will fit.
http://shop.ebay.co.uk/merchant/knobblybobbly_W0QQ...
d=114 f=900 - I presume this is the focal length? (Maybe talking crap here and tying to look intelligent).
Now, I would like to look at the Moon and distant starts and thats it - I am not interested in anything 'terrestrial' so to speak. So what one/two should I choose?
TA,
Its a Tasco 302012 Now, this chap is selling a load of them that he says will fit.
http://shop.ebay.co.uk/merchant/knobblybobbly_W0QQ...
d=114 f=900 - I presume this is the focal length? (Maybe talking crap here and tying to look intelligent).
Now, I would like to look at the Moon and distant starts and thats it - I am not interested in anything 'terrestrial' so to speak. So what one/two should I choose?
TA,
Edited by Morningside on Sunday 9th August 15:50
e mail these guys. http://www.telescopesandbinoculars.co.uk/acatalog/...
Telescope eyepieces generally come in two sizes - the really good quality expensive ones tend to be 2" and at the other end of the scale are 1.25". This size refers to the diameter of the telescope aperture that the eyepiece slots in to. Having said that 1.25" are at the bottom end of the scale, this is a bit of an over exaggeration, as you can pay a lot of money for eyepieces at this size, and they produce extremely good results.
It's almost certain that your scope will require a 1.25" eyepiece. The other measurement you need to consider is the eyepiece focal length. This is measured in mm and the smaller the number, the greater the magnification. Don't rush out to buy the smallest mm eyepiece you can find though, thinking that you want as much magnification as possible. To view the moon doesn't require great magnification, and eyepieces at the longer end of the scalewill also give you a wider angle of view, which makes them easier to use.
If you can afford a couple, I would start off with something like a 22mm and 15mm. If you want a bit more magnification for looking at some of the planets, a 9mm should be a good place to start.
It's almost certain that your scope will require a 1.25" eyepiece. The other measurement you need to consider is the eyepiece focal length. This is measured in mm and the smaller the number, the greater the magnification. Don't rush out to buy the smallest mm eyepiece you can find though, thinking that you want as much magnification as possible. To view the moon doesn't require great magnification, and eyepieces at the longer end of the scalewill also give you a wider angle of view, which makes them easier to use.
If you can afford a couple, I would start off with something like a 22mm and 15mm. If you want a bit more magnification for looking at some of the planets, a 9mm should be a good place to start.
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