Generic eyepieces - Yay or nay?

[StellariuS (Jayden)]

Evening guys,

Been looking around for a 2" eyepiece, I've come across a few, but they are cheap. I was wondering if someone could perhaps take a look and and help me determine if its worth it.

http://cgi.ebay.com/ws/eBayISAPI.dll...%3DI%26otn%3D2

This one is has a F/L around what I'm looking for, but will i be let down if i get it?

Any comments will be appreciated

[astro744]

Depends what telescope you intend on using it with and how old you are.

I have not seen the 15mm but the 30mm/80deg 1rpd is a fine well built solid eyepiece with a eye lens giving bright and clear images. However, it suffers from field curvature and the outer 30% particularly is out of focus when the centre is in focus. The severity of the curvature will depend on the focal length and ratio of your telescope. Whether your eye can adjust for the foucs will depend on your age, the younger the better. Not sure if the 15mm 1rpd would have the same field curvature as the 30mm.

The 30mm does Barlow well to give 15mm and perhaps the 15mm Barlows just as well to give a 7.5mm with 2" 2x Barlow. The eyepice will perform better in longer focal ratio telescopes.

[casstony]

Originally Posted by StellariuS

This one is has a F/L around what I'm looking for, but will i be let down if i get it?

"A world-class eyepiece. Don't worry! You're going to be surprised how good it is, including performance at the edge of the field"

If you believe the claims made by the seller you will probably be disappointed. This is a cheap range of eyepieces best suited to schmidt cassegrains. The 30mm is ok as an observing eyepiece in a SCT, and ok as a finder eyepiece in Newtonians. The 20mm is the 30mm eyepiece with a barlow element screwed on which makes the eyepiece perform better. I haven't used the other focal lengths but reviews I've read don't inspire confidence.

A 13mm hyperion or stratus would be far superior.

[StellariuS (Jayden)]

Cheers for the heads up guy. I'm still young so age isn't an issue for me. I'll be using it with my F/5 scope so perhaps ill get a bit of focus curvature. ill look around for one with a FL of 15mm or lower. I'd love a low mag wide field piece but if 30% will be out of focus i might just get me a 30-40mm 1.25" eyepiece.

thanks again

[casstony]

Here's a couple of links if you want to read about eyepieces Jayden:

http://www.astrosurf.com/luxorion/re...ons.htm#barrel size

http://www.quadibloc.com/science/opt04.htm

[astro744]

Originally Posted by StellariuS

Cheers for the heads up guy. I'm still young so age isn't an issue for me. I'll be using it with my F/5 scope so perhaps ill get a bit of focus curvature. ill look around for one with a FL of 15mm or lower. I'd love a low mag wide field piece but if 30% will be out of focus i might just get me a 30-40mm 1.25" eyepiece.

thanks again

I have only tried the 30mm 1rpd and not the 15mm 1rpd so results may vary. Being young your eye will adapt to the change in focus much faster and you may find the eyepiece works for you.

If you want a sharp but smaller apparent field you cannot go wrong with a Tele Vue 32mm Plossl as an alternative. The magification is about half though to that of the 15mm. A Tele Vue 20mm Plossl would also be a good choice to go with the 32. Note although the 32 will Barlow it will have a rather long eye relief when done so. A Powermate would be a better alternative to a Barlow for the 32mm.