Magnification Question

lalee17

Hey all, [by the way I've read the 'Observing tips for beginners' thread]
I bought a Celestron Astromaster 130 EQ telescope recently, and have observed the moon, and tonight viewed Mars. I was using a 10mm eyepiece, and it only appeared as a small bright orange-red dot.
Should I get a 4mm eyepiece for viewing other planets like Saturn and Venus?
Also, is the telescope I bought a decent one?
Thanks

backboiler

Telescope is 130 mm objective with 650 mm focal length (so f/5). 4 mm lens will give 650/4 magnification, about 160x. Usual guide is not to exceed magnification of twice the objective diameter in mm, so 260x in your case. You should be well within limits on the light-gathering side of things.
The thing about the 4 mm eyepiece is that it's very hard to get the focus spot on (even small adjustment of focus knob causes movement that is significant compared to 4 mm focal length). Also it's fairly difficult to line up your eye with the tiny aperture of a 4mm eyepiece.

That said I've used a 4 mm on a 102 mm f/10 (well beyond recommended limit) to view Jupiter and moons.

So personally I wouldn't spend a lot on a 4 mm eyepiece but if you could pick a half-decent one up cheaply then it would be handy to have.

djhaxman

A 2x barlow lens would double the magnification on your 10mm eyepiece to 130x giving you the same aperture.

A 3x barlow would give you 195x magnification. And barlows tend to be cheaper than eyepieces too.