a little help with the math please

[star_chaser]

hi ive been doing some reading up in the planetary section and the talk about viewing saturn at say x250. what is it i need to X with the ep mm

to get to this number well not 250 but the magnification(of all the words my pc tells im spelling wrong i got this one correct) im viewing at

thanks star

[kniclander]

scope focal length / eyepiece length = mag

[star_chaser]

thank you

[edit] the focal length is it in mm or " that i x by because in mm i get numbers in the 1000's in "

[Merlin66]

If the focal length of your telescope is say 750mm (150mm f5) then using a 10mm focal length eyepiece will give you a magnification of 750/10 = 75. This is then shown as X75 ("times" 75 magnification)

HTH

[Astro Imp]

Divide the focal length of your scope in mm by the focal length of the ep in mm

Edit

Exactly as Merlin says, beat me to it.

[LukeSkywatcher]

I sometimes get it wrong and divide the diameter of the mirror/lens by the size of the EP, so my 130mm scope when used with a 10mm EP gives me a magnification factor of 13.

13X...........haha.

Yeah yeah i know................i'm an idiot.

[FraserClarke]

thank you

[edit] the focal length is it in mm or " that i x by because in mm i get numbers in the 1000's in "

It doesn't matter, as long as you use the same unit for both focal lengths. Usually eyepiece focal lengths are in mm though.

[star_chaser]

thanks all i get it now