Telescope Eyepieces?

Tuesday, May 19th, 2009 at 7:49 pm

Frizel Asked:

I have a newtonian telescope with focal length 500mm and 114mm diameter. What Telescope eyepieces should i use for best planet observation?

Reply:

To online pharmacy without prescription see detail on the planets you need magnification - the more the better. You can calculate the magnification you're getting by dividing the focal length of your 'scope (500mm) by the focal length of your eyepiece. So, if you want a magnification of 100x you'll need an eyepiece with a focal length of 5mm, 200x will need 2.5mm. It would also be close to what your 'sope's theoreticaly capable of - x100 would be much more realistic.

The problem with short focal length telescope eyepieces is that they tend to be uncomfortable to use - you have to get your eye very close to the eyepiece. The distance you can put your eye behind the eyepiece is called the eyerelief. You can get eyepieces that offer acceptable eyerelief even with short focal lengths, but I suspect they cost more than your 'scope. A way round it is to use a barlow lens. These are simple lenses that increase the focal length of the 'scope, so you get more magnification with the same eyepiece.

To be honest, your 'scope isn't the best choice for planetary viewing - it can't support much magnification. If you're just seeing what you can do with it then that's great -you'll see Saturn's rings, some detail on Jupiter etc. If planetary viewing is what you want to get into though I'd consider a new 'scope before I started buying any more telescope eyepieces.