EP Help

[lepus]

Hi

I'm sure this question has been asked before so please forgive me for asking again!

I'm looking to purchase some new EP's my main interests are DSO's and planets.

Being at the back of the queue when the maths brains were being handed out I don't know what size EP's to buy I have a 70mm scope.

Thanks in advance

Kelly

[John]

For planets you generally need more magnification which means eyepieces with shorter focal lengths (the number in mm, eg: 5mm, 7mm etc). For DSO's the opposite is generally true (there are some exceptions though) so eyepieces with longer focal lengths such as 25mm, 32mm etc will give you the lower power views you need.

What focal length is your scope ?

[lepus]

Hi

900mm

[ronin]

70mm dia and 900 focal length will be f/13, (close).

If you want to look at DSO's then you will need fairly long focal length eyepieces.

I would say 20, 32 mm.

The 32 eyepiece use to locate the object as it will give a wider field of view.

With a scope that long I think that you will only need fairly long eyepieces.

A 13mm eyepiece should be fair for magnification and I would not go below say 10mm.

[michael.h.f.wilkinson]

You could go to even longer focal length EPs, but you will need to have a 2" eyepiece holder in your focuser, otherwise you will not get a decent sized field of view. If your focuser accepts 2" eyepieces, getting e.g. a 40 or 50mm would be great for DSOs.

[lepus]

Hi

Thanks for the advice.